5 6082617462954656629

((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) If R1 is the primary winding resistance and R2 is the secondary winding

resistance then the equivalent resistance of the transformer as referred to the
ENTER primary is
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) R1+ R2/K2

THIS IS
MANDATORY
OPTION
((OPTION_B)) R2+ R1/K2

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) R1+ K2R2

This is optional
((OPTION_D)) R2+ K2R

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION When secondary resistantance transferred? to primary..It is divided by Suare of

)) This is also k..
optional
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) The purpose of the transformer core is to provide ____________
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) High reluctance path

THIS IS
MANDATORY
OPTION
((OPTION_B)) Low reluctance path

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) High inductive path

This is optional
((OPTION_D)) High capacitive path

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION The purpose of a transformer core is to provide a low-reluctance path for the
)) This is also magnetic flux linking primary and secondary windings. In doing so, the core
optional experiences iron losses due to hysteresis and eddy currents flowing within it
which, in turn, show themselves as heating of the core material.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Transformer core is designed to reduce ______________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Hysteresis loss

THIS IS
MANDATORY
OPTION
((OPTION_B)) Eddy current loss

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Hysteresis loss and Eddy current loss

This is optional
((OPTION_D)) Cannot be determined

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION Hysteresis loss and eddy current loss are the losses which take place in core of
)) This is also the transformer thus they are also termed as core losses. While other losses
optional take place in winding or in air gap which can’t be dealt with core design.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Transformers windings are generally made of __________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Steel
THIS IS
MANDATORY
OPTION
((OPTION_B)) Steel
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Copper
This is optional
((OPTION_D)) Steel iron alloy

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION In order to avoid losses due to loading current, winding materials must be
)) This is also chosen wisely. Winding conductors are thus made of copper or more precisely
optional saying they are made of high conductivity copper by some industrial processes.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Transformer ratings are given in _____________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) kW
THIS IS
MANDATORY
OPTION
((OPTION_B)) kVAR
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) HP
This is optional
((OPTION_D)) kVA
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION There are two types of losses in a transformer, Copper Losses and Iron Losses or
)) This is also Core Losses or Insulation Losses. Copper losses (I2R) depends on current passing
optional through transformer winding while Iron losses or Core Losses or Insulation
Losses depends on Voltage. That’s why the rating of Transformer is in kVA.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Primary winding of a transformer ______________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Is always a high voltage winding

THIS IS
MANDATORY
OPTION
((OPTION_B)) Is always a low voltage winding

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Could either be a low voltage or high voltage winding

This is optional

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION Primary winding used in a transformer, can be at higher or lower voltage

)) This is also potential, depending on the number of turns with secondary winding. For step
optional up and step-down transformers primary winding will be at lower and higher
potential respectively.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) If a transformer is having equal number of turns at primary and secondary then
transformer is called as _______________
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Step-down
THIS IS
MANDATORY
OPTION
((OPTION_B)) Step-up
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) One-one
This is optional
((OPTION_D)) Autotransformer
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION A transformer is having equal number of turns at primary and secondary then
)) This is also transformer is called as one-one transformer. This transformer have turns ratio
optional equal to 1, so is the voltage ratio for the one-one transformer.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Sandwiched type of winding is used in ____________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) In all transformers

THIS IS
MANDATORY
OPTION
((OPTION_B)) In core type transformers

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) In shell type transformers

This is optional
((OPTION_D)) In all transformers except shell and core type transformers

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION According to the construction of transformers core type transformers don’t

)) This is also require sandwiched wiring. While, in the shell type transformer, the primary and
optional secondary windings pass inside the steel magnetic circuit (core) which forms a
shell around the winding.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) A transformer cannot work on the DC supply because __________________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) There is no need to change the DC voltage

THIS IS
MANDATORY
OPTION
((OPTION_B)) A DC circuit has more losses

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Faraday’s laws of electromagnetic induction are not valid since the rate of
change of flux is zero
This is optional

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION For DC supply the direction and the magnitude of the supply remains constant,
)) This is also produced flux will be constant. Thus, rate of change of flux through the windings
optional will be equal to zero. As a result, voltage at secondary will always be equal to 0.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) For DC supply the direction and the magnitude of the supply remains constant,
produced flux will be constant. Thus, rate of change of flux through the windings
ENTER will be equal to zero. As a result, voltage at secondary will always be equal to 0.
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) True
THIS IS
MANDATORY
OPTION
((OPTION_B)) False
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C))
This is optional
((OPTION_D))
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION The primary and secondary windings have zero resistance. It means that there is
)) This is also no ohmic power loss and no resistive voltage drop in the ideal transformer. An
optional actual transformer has finite but small winding resistances.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Identify the correct statement relating to the ideal transformer.

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) no losses and magnetic leakage

THIS IS
MANDATORY
OPTION
((OPTION_B)) a common core for its primary and secondary windings

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) interleaved primary and secondary windings

This is optional
((OPTION_D)) interleaved primary and secondary windings

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION There is no leakage flux so that all the flux is confined to the core and links both
)) This is also the windings. An actual transformer does have a small amount of leakage flux
optional which can be accounted in detailed analysis by appropriate circuit modelling.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) An ideal transformer will have maximum efficiency at a load such that
_____________
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) copper loss = iron loss

THIS IS
MANDATORY
OPTION
((OPTION_B)) copper loss < iron loss

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) copper loss > iron loss

This is optional
((OPTION_D)) cannot be determined

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION Maximum efficiency of a transformer is defined at the that values when, copper
)) This is also losses become completely equal to the iron losses. In all other cases the
optional efficiency will be lower than the maximum value.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) What is the no-load current drawn by transformer?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) 0.2 to 0.5 per cent

THIS IS
MANDATORY
OPTION
((OPTION_B)) 2 to 5 per cent

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) 2 to 5 per cent

This is optional
((OPTION_D)) 20 to 30 per cent

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION The no load current is about 2-5% of the full load current and it accounts for the
)) This is also losses in a transformer. These no-load losses include core(iron/fixed) losses,
optional which contains eddy current losses & hysteresis losses and the copper(I2*R)
losses due to the no Load current.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Purpose of no-load test on a transformer is ___________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Copper loss

THIS IS
MANDATORY
OPTION
((OPTION_B)) Magnetising current

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Magnetising current and loss

This is optional
((OPTION_D)) Efficiency of the transformer

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION No-load current is little bit greater than actual magnetizing current. Total no-
)) This is also load current supplied from the source has two components, one is magnetizing
optional current which is utilized for magnetizing the core and other component is
consumed for compensating the core losses in transformer.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Greater the secondary leakage flux ___________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) less will be the secondary induced emf

THIS IS
MANDATORY
OPTION
((OPTION_B)) less will be the primary induced emf

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) less will be the primary induced emf

This is optional
((OPTION_D)) cannot be determined

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION Since emf induced in the transformer coils is directly proportional to the change
)) This is also in the flux with respect to time, we can say that if flux reduces the change in flux
optional after some time will be less which will induce less voltage in secondary.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) In a given transformer for given applied voltage, which of the following losses
remain constant irrespective of load changes?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Friction and windage losses

THIS IS
MANDATORY
OPTION
((OPTION_B)) Copper losses

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Hysteresis and eddy current losses

This is optional

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION Hysteresis and eddy current losses together called as core-loss in a transformer.
)) This is also These losses remain constant for constant voltage and frequency applied to a
optional transformer, these components remain same irrespective of load.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Leakage flux in the transformer depends on _____________________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Load current

THIS IS
MANDATORY
OPTION
((OPTION_B)) Load current and voltage

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Load current, voltage and frequency

This is optional
((OPTION_D)) Load current, voltage and frequency

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION Leakage flux is directly proportional to the current, as if is current increased net
)) This is also value of flux increases thus, flux leakage also increases which further contribute
optional to the losses as it is then not able to link with secondary windings .
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) The full-load copper loss of a transformer is 1600 W. At half-load, the copper
loss will be
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) 6400 W
THIS IS
MANDATORY
OPTION
((OPTION_B)) 1600 W
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) 800 W
This is optional
((OPTION_D)) 400 W
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION Copper losses are defined as I2*R losses many times, as they are directly
)) This is also proportional to the square of current flowing through them. Thus, copper losses
optional will reduce if load is reduced that too in square proportion.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) While conducting short-circuit test on a transformer which side is short

circuited?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) High voltage side

THIS IS
MANDATORY
OPTION
((OPTION_B)) Low voltage side

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Primary side

This is optional
((OPTION_D)) Secondary side

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION It’s a common practice to conduct SC test from HV side, while keeping LV side
)) This is also short circuited. Thus, short circuited current is made to flow from shorted low
optional voltage terminals i.e. LV side.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) During short circuit test why iron losses are negligible?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) The current on secondary side is negligible

THIS IS
MANDATORY
OPTION
((OPTION_B)) The voltage on secondary side does not vary

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) The voltage applied on primary side is low

This is optional
((OPTION_D)) Full-load current is not supplied to the transformer

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION Very small amount of voltage is given to the transformer primary thus the
)) This is also magnetic losses which are dependent on magnetic flux density will get minimum
optional value, hence iron losses are negligible.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Short circuit test on transformers is conducted to determine ______

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Core losses

THIS IS
MANDATORY
OPTION
((OPTION_B)) Copper losses

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Hysteresis losses

This is optional
((OPTION_D)) Eddy current losses

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION Short circuit test is used to determine the copper losses taking place in the
)) This is also transformer under operation, while open circuit test gives us the value of core
optional losses taking place in the transformer.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) The purpose of the transformer core is to provide ____________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) High reluctance path

THIS IS
MANDATORY
OPTION
((OPTION_B)) Low reluctance path

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) High inductive path

This is optional
((OPTION_D)) High capacitive path

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION The purpose of a transformer core is to provide a low-reluctance path for the
)) This is also magnetic flux linking primary and secondary windings. In doing so, the core
optional experiences iron losses due to hysteresis and eddy currents flowing within it
which, in turn, show themselves as heating of the core material.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Transformer core is designed to reduce ______________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Hysteresis loss

THIS IS
MANDATORY
OPTION
((OPTION_B)) Eddy current loss

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Hysteresis loss and Eddy current loss

This is optional

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION Hysteresis loss and eddy current loss are the losses which take place in core of
)) This is also the transformer thus they are also termed as core losses. While other losses
optional take place in winding or in air gap which can’t be dealt with core design.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Transformers windings are generally made of __________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Steel
THIS IS
MANDATORY
OPTION
((OPTION_B)) Iron
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Copper
This is optional
((OPTION_D)) Steel iron alloy

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION In order to avoid losses due to loading current, winding materials must be
)) This is also chosen wisely. Winding conductors are thus made of copper or more precisely
optional saying they are made of high conductivity copper by some industrial processes.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Transformer ratings are given in _____________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) kW
THIS IS
MANDATORY
OPTION
((OPTION_B)) kVAR
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) HP
This is optional
((OPTION_D)) kVA
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION There are two types of losses in a transformer, Copper Losses and Iron Losses or
)) This is also Core Losses or Insulation Losses. Copper losses (I2R) depends on current passing
optional through transformer winding while Iron losses or Core Losses or Insulation
Losses depends on Voltage. That’s why the rating of Transformer is in kVA.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Function of transformer is to _________________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Convert AC to DC
THIS IS
MANDATORY
OPTION
((OPTION_B)) Convert DC to AC
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Step down or up the DC voltages and currents

This is optional
((OPTION_D)) Step down or up the AC voltages and currents

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION A Transformer does not work on DC and operates only on AC, therefore it Step
)) This is also up of Step down the level of AC Voltage or Current, by keeping frequency of the
optional supply unaltered on the secondary side.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Transformer core is generally made of ___________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Single block of core material

THIS IS
MANDATORY
OPTION
((OPTION_B)) By stacking large number of sheets together

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Can be made with any of the above method

This is optional

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION Transformer core experiences eddy current losses when transformer is in the
)) This is also operations. In order to reduce eddy current losses, it is advisable to use large
optional number of sheets laminated from each other are stick together than using one
single block.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Transformer core is constructed for ______________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Providing least effective magnetic linkage between two windings

THIS IS
MANDATORY
OPTION
((OPTION_B)) Providing isolation between magnetic linkages of one coil from another
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Providing most effective magnetic linkage between two windings

This is optional

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION Transformer core is so chosen that it will provide low reluctance path and will
)) This is also transfer maximum amount of flux from one winding to other, providing most
optional effective magnetic linkage between two windings.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Which of the following statements is/are correct?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) High frequency power supplies are light weight

THIS IS
MANDATORY
OPTION
((OPTION_B)) Transformer size gets reduced at high frequency

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Transformer size is more at higher frequency

This is optional
((OPTION_D)) High frequency power supplies are light weight and transformer size gets
reduced at high frequency
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION From the induced emf equation of transformer emf is given by E ∝ φf. For same
)) This is also emf, φf = constant φ1f1 = φ2f2 i.e. B1A1f1 = B2A2f2. For constant flux density B1 =
optional B2. A1f1 = A2f2. For high frequency f2 > f1, A2 < A1. Thus, at high frequencies
transformer size get reduced and also light weight.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Transformer operating at 25-400 Hz frequency contain core made of

_____________
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Highly permeable iron

THIS IS
MANDATORY
OPTION
((OPTION_B)) Steel alloy

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Air core

This is optional
((OPTION_D)) Highly permeable iron and Steel alloy

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION When core is made of highly permeable iron or steel alloy (cold-rolled, grain
)) This is also oriented sheet steel). This transformer is generally called an iron-core
optional transformer. Transformers operated from 25–400 Hz are invariably of iron-core
construction.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Which type of flux does transformer action need?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Constant magnetic flux

THIS IS
MANDATORY
OPTION
((OPTION_B)) Increasing magnetic flux

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Alternating magnetic lux

This is optional
((OPTION_D)) Alternating electric flux

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION The energy transfer in a transformer, is from one winding to another, entirely
)) This is also through magnetic medium it is known as transformer action. Therefore,
optional transformer action requires an alternating or time varying magnetic flux in order
to transfer power from primary side to secondary side. Since induced emf in the
winding is due to flux linkage.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Different core construction is required for core type and shell type transformer
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) True
THIS IS
MANDATORY
OPTION
((OPTION_B)) False
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C))
This is optional
((OPTION_D))
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION In the “closed-core” type transformer, the primary and secondary windings are
)) This is also wound outside and surround the core ring. In the “shell type” transformer, the
optional primary and secondary windings pass inside the steel magnetic circuit (core)
which forms a shell around the windings.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) here is only one magnetic flux path in the circuit. The transformer is definitely
________________
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Core type

THIS IS
MANDATORY
OPTION
((OPTION_B)) Shell type

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Can be any of the above

This is optional
((OPTION_D)) Depends on other parameters

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION In core type transformer, winding is placed on two core limbs, while in case of
)) This is also shell type transformer, winding is placed on mid arm of the core. Other limbs
optional will be used as mechanical support. Core type transformers have only one
magnetic flux path.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Which of the following is correct statement?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Core type transformer has more output than shell type
THIS IS
MANDATORY
OPTION
((OPTION_B)) Core type transformer has higher efficiency compare to shell type
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Core type transformer has lower efficiency than shell type
This is optional
((OPTION_D)) Can’t predict

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
In core type winding is surrounded with considerable part of core whereas in

((EXPLANATION shell type core is surrounded with considerable part of winding of transformer.
)) This is also In core type output is less, because of losses. In shell type transformer output is
optional high because of less loss, thus efficiency will be more in case of shell
transformer.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Core type transformer is with ____________________
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Large size

THIS IS
MANDATORY
OPTION
((OPTION_B)) Small size

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) High voltage

This is optional
((OPTION_D)) Everywhere
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION Core type is very useful when we need large size of the transformer with
)) This is also operation at low voltage. While shell type transformer is very useful when we
optional need small size high voltage. Cooling is more in core type.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Which of the following is the correct statement?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Shell type has more mechanical protection

THIS IS
MANDATORY
OPTION
((OPTION_B)) Cooling is more in shell type

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) In core type sandwiched wiring is used

This is optional
((OPTION_D)) In core type concentric winding is used

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION Shell type has less mechanical protection to coil while Core type has better
)) This is also mechanical protection to coil. Core type is easy to repair and maintain. In core
optional type transformer concentric cylindrical winding are used. In shell type
transformer sandwiched winding are used.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) What is the purpose of providing an iron core in a transformer?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Provide support to windings

THIS IS
MANDATORY
OPTION
((OPTION_B)) Reduce hysteresis loss

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Decrease the reluctance of the magnetic path

This is optional
((OPTION_D)) Reduce eddy current losses

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION Iron core is used in a transformer to carry flux from one winding to another
)) This is also winding, so there should be minimum opposition to flux passing through iron
optional core. Hence, transformer function is to decrease the reluctance of magnetic
path.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Primary winding of a transformer ______________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Is always a high voltage winding

THIS IS
MANDATORY
OPTION
((OPTION_B)) Is always a low voltage winding

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Could either be a low voltage or high voltage winding

This is optional

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D
or E
((EXPLANATION Primary winding used in a transformer, can be at higher or lower voltage

)) This is also potential, depending on the number of turns with secondary winding. For step
optional up and step-down transformers primary winding will be at lower and higher
potential respectively.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Which winding has more number of turns?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Low voltage winding

THIS IS
MANDATORY
OPTION
((OPTION_B)) High voltage winding

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Primary winding

This is optional
((OPTION_D)) Secondary winding

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
B
((CORRECT_CH
OICE)) Either A
or B or C or D or
E
((EXPLANATION High voltage winding always has a large number of turns, as voltage is directly
)) This is also proportional to the number of turns. If large numbered winding is present on
optional primary side then the transformer is step down transformer.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) For an ideal transformer the winding should have

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) maximum resistance on primary side and least resistance on secondary side
THIS IS
MANDATORY
OPTION
((OPTION_B)) minimum resistance on primary side and maximum resistance on secondary side
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) equal resistance on primary and secondary side

This is optional
((OPTION_D)) no ohmic resistance on either side

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
D
((CORRECT_CH
OICE)) Either A
or B or C or D or
E
((EXPLANATION For an ideal transformer the losses should be zero on both sides. Therefore the
)) This is also ohmic resistance on either side of the transformer should be equal to zero.
optional
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Which of the following statements is/are correct statements?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) EMF per turn in HV winding is more than EMF per turn in LV winding
THIS IS
MANDATORY
OPTION
((OPTION_B)) EMF per turn in HV winding is less than EMF per turn in LV winding
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) EMF per turn in both the windings are equal

This is optional
((OPTION_D)) all of the above

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
C
((CORRECT_CH
OICE)) Either A
or B or C or D or
E
((EXPLANATION In a transformer primary volt-ampere is equal to secondary volt-ampere and

)) This is also primary ampere turns are also equal to secondary ampere turns. So, EMF per
optional turn in both the windings is equal. Total induced emf on both sides depends on
the number of turns, flux and frequency. If number of turns on secondary is
more than primary, then emf induced in the secondary will be more than
primary side and vice versa, but the emf per turn in both the windings is equal.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) The core flux in transformer depends mainly on

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) supply voltage

THIS IS
MANDATORY
OPTION
((OPTION_B)) supply voltage and frequency

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) supply voltage, frequency and load

This is optional
((OPTION_D)) supply voltage and load
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION Therefore core flux in transformer depends mainly on supply voltage and
)) This is also frequency.
optional
((MARKS)) 2
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) If the applied voltage of a certain transformer is increased by 50% and the
frequency is reduced by 50%, the maximum flux density will (assuming that the
ENTER magnetic circuit remains unsaturated)
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) changes to three times the original value

THIS IS
MANDATORY
OPTION
((OPTION_B)) changes to 1.5 times the original value

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) changes to 0.5 times the original value

This is optional
((OPTION_D)) remain the same as the original

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION
)) This is also
optional
((MARKS)) 2
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) The low voltage winding of a 400/230 V single phase 50 Hz transformer is to be

connected to keep the magnetization current at the same level in both the cases
ENTER the voltage at 25 Hz should be
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) 230 V
THIS IS
MANDATORY
OPTION
((OPTION_B)) 460 V
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) 115 V
This is optional
((OPTION_D)) 65 V
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION To maintain the magnetization current at the same level, flux φ should be same
)) This is also
optional
i.e V/f ratio should be same.
((MARKS)) 2
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) A single phase transformer has specifications as 250 KVA, 11000 V/415 V, 50 Hz.
What are the values of primary and secondary currents?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) primary = 22.7 A, secondary = 602.4 A

THIS IS
MANDATORY
OPTION
((OPTION_B)) primary = 602 A, secondary = 22.7 A

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) primary = 301 A, secondary = 22.7 A
This is optional
((OPTION_D)) primary = 11.4 A, secondary = 301 A

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION
)) This is also
optional
((MARKS)) 2
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) R1 is the resistance of the primary winding of the transformer. The turn ratio in
terms of primary to secondary is K. Then the equivalent resistance of the
ENTER primary referred to secondary is
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) R1 /K
THIS IS
MANDATORY
OPTION
((OPTION_B)) K²R1
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) R1 /K²
This is optional
((OPTION_D)) K×R1
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION By changing of primary parameters to secondary or vice versa it does not change
)) This is also the performance of circuit. So that we are taking power rating are equal in
optional
before and after referring.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Voltage regulation of transformer is given by
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) (E2 - V2) / V2

THIS IS
MANDATORY
OPTION
((OPTION_B)) (E2 - V2) / E2

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) (V2 - E2) / V2

This is optional
((OPTION_D)) (V2 - E2) / E2

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION Voltage regulation is defined as the change in terminal voltage when the rated
)) This is also load at a given power factor is disconnected across the terminals expressed in
optional terms of rated secondary voltage.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) In a transformer zero voltage regulation is achieved at a load power factor which
is
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) zero
THIS IS
MANDATORY
OPTION
((OPTION_B)) unity
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) lagging
This is optional
((OPTION_D)) leading
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION At leading power factor the voltage regulation can be negative or zero. This can
)) This is also be found from this equation % regulation = εxcosθ - εrsinθ
optional
((MARKS)) 2
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) A transformer has resistance and reactance in per unit as 0.01 and 0.04
respectively. Its voltage regulation for 0.8 power factor lagging and leading will
ENTER be
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) 6% and -4%

THIS IS
MANDATORY
OPTION
((OPTION_B)) 3.2% and -1.6%

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) 4.8% and -3.2%

This is optional
((OPTION_D)) none of the above

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION Voltage regulation for lagging power factor = (R cosθ + X sinθ)×100 Voltage
)) This is also regulation for 0.8 lagging power factor = (0.01×0.8+0.04×0.6)×100 = 3.2%
optional Voltage regulation for leading power factor = (R cosθ - X sinθ)×100 Voltage
regulation for 0.8 leading power factor = (0.01×0.8 - 0.04×0.6)×100 = -1.6%
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) The constant losses in transformer is/are

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) copper loss.

THIS IS
MANDATORY
OPTION
((OPTION_B)) eddy current loss.

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) hysteresis loss.

This is optional
((OPTION_D)) both 2 and 3.

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION Eddy current loss and hysteresis loss are almost independent of load,
)) This is also significantly depending on supply voltage and frequency. As the flux density or
optional flux is constant for a given voltage and frequency, eddy current loss and
hysteresis loss remain constant at any load. Therefore, these losses are called
constant losses. Copper loss varies as the square of load current and called
variable loss.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) In a transformer, hysteresis and eddy current losses depend upon
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) load current

THIS IS
MANDATORY
OPTION
((OPTION_B)) maximum flux density

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) supply frequency

This is optional
((OPTION_D)) both 2 and 3

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION both 2 and 3

)) This is also
optional
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) In a transformer operating at constant voltage if the input frequency increases,
the core loss
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) increase.
THIS IS
MANDATORY
OPTION
((OPTION_B)) decrease.
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) remains constant.

This is optional
((OPTION_D)) none of the above.

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION
)) This is also
optional
1. Transformer core is generally made of ___________
a) Single block of core material
b) By stacking large number of sheets together
c) Can be made with any of the above method
d) Cannot be determined
View Answer
Answer: b
Explanation: Transformer core experiences eddy current losses when transformer is in the
operations. In order to reduce eddy current losses, it is advisable to use large number of
sheets laminated from each other are stick together than using one single block.
2. Transformer core is constructed for ______________

a) Providing least effective magnetic linkage between two windings
b) Providing isolation between magnetic linkages of one coil from another
c) Providing most effective magnetic linkage between two windings
View Answer
Answer: c
Explanation: Transformer core is so chosen that it will provide low reluctance path and will
transfer maximum amount of flux from one winding to other, providing most effective
magnetic linkage between two windings.
3. Which of the following statements is/are correct?

a) High frequency power supplies are light weight
b) Transformer size gets reduced at high frequency
c) Transformer size is more at higher frequency
d) High frequency power supplies are light weight and transformer size gets reduced at high
frequency
View Answer
Answer: d
Explanation: From the induced emf equation of transformer emf is given by E ∝ φf. For same
emf, φf = constant φ1f1 = φ2f2 i.e. B1A1f1 = B2A2f2. For constant flux density B1 = B2. A1f1 =
A2f2. For high frequency f2 > f1, A2 < A1. Thus, at high frequencies transformer size get
reduced and also light weight.
4. Transformer operating at 25-400 Hz frequency contain core made of _____________

a) Highly permeable iron
b) Steel alloy
c) Air core
d) Highly permeable iron and Steel alloy
View Answer
Answer: d
Explanation: When core is made of highly permeable iron or steel alloy (cold-rolled, grain
oriented sheet steel). This transformer is generally called an iron-core transformer.
Transformers operated from 25–400 Hz are invariably of iron-core construction.
5. In various radio devices and testing instruments we use ______________

a) Iron core transformer
b) Air core transformer
c) W/O core transformer
d) Any transformer can be used
View Answer
Answer: a
Explanation: In special cases, the magnetic circuit linking the windings may be made of
nonmagnetic material, in which case the transformer is referred to as an air-core transformer.
The air-core transformer is of interest mainly in radio devices and in certain types of
measuring and testing instruments.
6. Which type of flux does transformer action need?

a) Constant magnetic flux
b) Increasing magnetic flux
c) Alternating magnetic lux
d) Alternating electric flux
View Answer
Answer: c
Explanation: The energy transfer in a transformer, is from one winding to another, entirely
through magnetic medium it is known as transformer action. Therefore, transformer action
requires an alternating or time varying magnetic flux in order to transfer power from primary
side to secondary side. Since induced emf in the winding is due to flux linkage.
7. Different core construction is required for core type and shell type transformer.
a) True
b) False
View Answer
Answer: a
Explanation: In the “closed-core” type transformer, the primary and secondary windings are
wound outside and surround the core ring. In the “shell type” transformer, the primary and
secondary windings pass inside the steel magnetic circuit (core) which forms a shell around
the windings.
8. There is only one magnetic flux path in the circuit. The transformer is definitely
________________
a) Core type
b) Shell type
c) Can be any of the above
d) Depends on other parameters
View Answer
Answer: a
Explanation: In core type transformer, winding is placed on two core limbs, while in case of
shell type transformer, winding is placed on mid arm of the core. Other limbs will be used as
mechanical support. Core type transformers have only one magnetic flux path.
9. Which of the following is correct statement?

a) Core type transformer has more output than shell type
b) Core type transformer has higher efficiency compare to shell type
c) Core type transformer has lower efficiency than shell type
d) Can’t predict
View Answer
Answer: c
Explanation: In core type winding is surrounded with considerable part of core whereas in
shell type core is surrounded with considerable part of winding of transformer. In core type
output is less, because of losses. In shell type transformer output is high because of less loss,
thus efficiency will be more in case of shell transformer.
10. Core type transformer is with ____________________

a) Large size
b) Small size
c) High voltage
d) Everywhere
View Answer
Answer: a
Explanation: Core type is very useful when we need large size of the transformer with
operation at low voltage. While shell type transformer is very useful when we need small size
high voltage. Cooling is more in core type.
11. Which of the following is the correct statement?

a) Shell type has more mechanical protection
b) Cooling is more in shell type
c) In core type sandwiched wiring is used
d) In core type concentric winding is used
View Answer
Answer: d
Explanation: Shell type has less mechanical protection to coil while Core type has better
mechanical protection to coil. Core type is easy to repair and maintain. In core type
transformer concentric cylindrical winding are used. In shell type transformer sandwiched
winding are used.
12. What is the purpose of providing an iron core in a transformer?
a) Provide support to windings
b) Reduce hysteresis loss
c) Decrease the reluctance of the magnetic path
d) Reduce eddy current losses
View Answer
Answer: c
Explanation: Iron core is used in a transformer to carry flux from one winding to another
winding, so there should be minimum opposition to flux passing through iron core. Hence,
transformer function is to decrease the reluctance of magnetic path.
13. What is the thickness of laminations used in a transformer?

a) 0.1 mm to 0.5 mm
b) 4 mm to 5 mm
c) 14 mm to 15 mm
d) 25 mm to 40 mm
View Answer
Answer: a
Explanation: Laminations are made to reduce the eddy currents and is made of thin strips.
Generally, the steel transformer lamination range for 50 Hz varies from 0.25mm to 0.5mm, if
it is a 60 Hz transformer then it ranges from 0.17–0.27mm
1. In the transformer which of the following winding has got more cross-sectional area?
a) Copper winding
b) Steel winding
c) Aluminium winding
d) Iron winding
View Answer
Answer: a
Explanation: The wire used for carrying current in a transformer winding is either copper or
aluminium. While aluminium wire is lighter and less expensive than copper wire, a larger
cross-sectional area of conductor must be used to carry the same amount of current as with
copper.
2. Primary winding of a transformer ______________

a) Is always a high voltage winding
b) Is always a low voltage winding
c) Could either be a low voltage or high voltage winding
View Answer
Answer: c
Explanation: Primary winding used in a transformer, can be at higher or lower voltage
potential, depending on the number of turns with secondary winding. For step up and step-
down transformers primary winding will be at lower and higher potential respectively.
3. Which winding has more number of turns?

a) Low voltage winding
b) High voltage winding
c) Primary winding
d) Secondary winding
View Answer
Answer: b
Explanation: High voltage winding always has a large number of turns, as voltage is directly
proportional to the number of turns. If large numbered winding is present on primary side
then the transformer is step down transformer.
4. Part of the transformer which undergoes most damage from overheating is ___________
a) Iron core
b) Copper winding
c) Winding insulation
d) Frame or case
View Answer
Answer: c
Explanation: Copper windings carry current through them. The heat loss producing in any
winding carrying current is proportional to the square of the current passing through it
multiplied with resistance. For large transformers, current is very high, so heating causes
most of the damage to insulation material.
5. If a transformer is continuously operated the maximum temperature rise will occur in

___________
a) Core
b) Windings
c) Tank
View Answer
Answer: b
Explanation: Copper windings carry currents in a transformer. The loss in form of heat in
copper winding carrying current is proportional to the square of the current passing through
them multiplied by the resistance of the winding. This loss is dissipated in heat and
corresponding temperature rise.
6. If secondary number of turns are higher then, transformer is called _________

a) Step-down
b) Step-up
c) One-one
d) Autotransformer
View Answer
Answer: b
Explanation: When secondary number of turns are higher compare to primary, voltage
induced in secondary windings will obviously high. Thus, this transformer is used for
stepping up the output voltage by keeping frequency constant.
7. If primary number of turns are higher then, transformer is called _________

a) Step-down
b) Step-up
c) One-one
d) Autotransformer
View Answer
Answer: a
Explanation: When primary number of turns are higher compare to secondary, voltage
induced in secondary windings will obviously low compare to primary. Thus, this
transformer is used for stepping down the output voltage by keeping frequency constant.
8. If a transformer is having equal number of turns at primary and secondary then transformer
is called as _______________
a) Step-down
b) Step-up
c) One-one
d) Autotransformer
View Answer
Answer: c
Explanation: A transformer is having equal number of turns at primary and secondary then
transformer is called as one-one transformer. This transformer have turns ratio equal to 1, so
is the voltage ratio for the one-one transformer.
9. One to one transformers are used because ______________

a) To isolate any part of circuit electrically
b) To get more voltage at secondary
c) To get less voltage at secondary
d) To reduce losses, present in circuit
View Answer
10. Same type and kind of insulations are not used in all types of transformers.
a) True
b) False
View Answer
Answer: a
Explanation: The windings of huge power transformers use conductors with heavier
insulation and are assembled with greater mechanical support and the winding layers are
insulated from each other, this is known as minor insulation for which pressed board or
varnished cloth is used. While for major insulation and insulating cylinders, they are made of
specially selected pressed board or synthetic resin bounded cylinders, is used between LV
and core and LV and HV.
11. Sandwiched type of winding is used in ____________

a) In all transformers
b) In core type transformers
c) In shell type transformers
d) In all transformers except shell and core type transformers
View Answer
Answer: c
Explanation: According to the construction of transformers core type transformers don’t
require sandwiched wiring. While, in the shell type transformer, the primary and secondary
windings pass inside the steel magnetic circuit (core) which forms a shell around the winding.
1. What is the no-load current drawn by transformer?

a) 0.2 to 0.5 per cent
b) 2 to 5 per cent
c) 12 to 15 per cent
d) 20 to 30 per cent
View Answer
Answer: b
Explanation: The no load current is about 2-5% of the full load current and it accounts for the
losses in a transformer. These no-load losses include core(iron/fixed) losses, which contains
eddy current losses & hysteresis losses and the copper(I2*R) losses due to the no Load
current.
2. Purpose of no-load test on a transformer is ___________
a) Copper loss
b) Magnetising current
c) Magnetising current and loss
d) Efficiency of the transformer
View Answer
Answer: c
Explanation: No-load current is little bit greater than actual magnetizing current. Total no-
load current supplied from the source has two components, one is magnetizing current which
is utilized for magnetizing the core and other component is consumed for compensating the
core losses in transformer.
3. No-load current in a transformer ________________

a) Lags behind the voltage by about 75°
b) Leads the voltage by about 75°
c) Lags behind the voltage by about 15°
d) Leads the voltage by about 15°
View Answer
Answer: a
Explanation: No-load current lags behind the voltage by an angle which is near to 900. Thus,
angle between no-load current and magnetizing current is very small. No-load current has
another component which is in phase with voltage.
4. Which of the following statement is true for no-load current of the transformer?
a) has high magnitude and low power factor
b) has high magnitude and high power factor
c) has small magnitude and high power factor
d) has small magnitude and low power factor
View Answer
Answer: d
Explanation: Since no-load current lags voltage by the angle of nearly 900, power factor
being equal to cosine of the angle between current and voltage, it will be equal to value which
is near to 0. Thus, power factor will be low.
5. In no-load test we keep secondary terminals __________

a) Shorted
b) Shorted via fixed resistor
c) Open
d) Shorted via variable resistors
View Answer
Answer: c
Explanation: In no-load test, as we don’t require any load, we are not allowed to connect any
resistor (fixed/variable) to the transformer secondary. We don’t short the secondary terminals
either.
6. Maximum value of flux established in a transformer on load is equal to _________

a) E1/ (4.44*f*N1)
b) E1/ (4.44*f*N2)
c) E2/ (4.44*f*N1)
d) Cannot define
View Answer
Answer: a
Explanation: E1/ (4.44*f*N1). The emf induced in the primary due to applied voltage to
primary winding is equal to change in flux with respect to time multiplied by number of turns
in the primary. So, by solving this equation we get, E1= (4.44*f*φ*N1).
7. Induced emf in the primary of transformer is equal to terminal voltage applied at primary.
a) True
b) False
View Answer
Answer: a
Explanation: Induced emf in the primary is approximately equal to the applied voltage.
Ideally there lies a very small difference in the values, but it is neglected because winding
resistance in the transformer is of very small order.
8. For a linear B-H relationship, which option is correct?

a) The exciting current is equal to core loss current
b) The exciting current is equal to magnetizing current
c) The exciting current is equal to de-magnetizing current
d) The exciting current is equal to cross-magnetizing current
View Answer
Answer: b
Explanation: For a linear B-H relationship it is assumed that, there are no losses present in the
core like eddy current losses and hysteresis losses are neglected. Thus, core loss current is
equal to 0, which ultimately confirms exciting current is purely magnetizing one.
9.Third harmonic current in transformer at no-load is ______________

a) 3% of exciting current
b) 10% of exciting current
c) 25% of exciting current
d) 35% of exciting current
View Answer
Answer: d
Explanation: The effect of saturation nonlinearity is to create a family of odd-harmonic
components in the exciting current, the predominant being the third harmonic; this may
constitute as large as 35–40% of the exciting current.
10. Ii in no-load test is responsible for ______________

a) Production of flux
b) Reactive power drawn from the supply
c) Active power drawn from the supply
d) No significance
View Answer
Answer: c
Explanation: It will be assumed here that the current Io and its magnetizing component Im
and its core-loss component Ii are sinusoidal on equivalent rms basis. In other words, Im is
the magnetizing current and is responsible for the production of flux, while Ii is the core-loss
current responsible for the active power being drawn from the source to provide the
hysteresis and eddy-current loss.
11. The parallel circuit model is drawn because _________________

a) Conductance Gi accounts for core-loss current
b) Inductive susceptance Bm accounts for magnetizing current
c) Gi for core – loss current and Bm for magnetizing current
d) Cannot say
View Answer
Answer: c
Explanation: The parallel circuit model of exciting current can be easily imagined wherein
conductance Gi accounts for core-loss current Ii and inductive susceptance Bm for
magnetizing current Im. Both these currents are drawn at induced emf E1 = V1 for resistance-
less, no-leakage primary coil; even otherwise E1 =V1.
1. A transformer cannot work on the DC supply because __________________

a) There is no need to change the DC voltage
b) A DC circuit has more losses
c) Faraday’s laws of electromagnetic induction are not valid since the rate of change of flux is
zero
View Answer
Answer: c
Explanation: For DC supply the direction and the magnitude of the supply remains constant,
produced flux will be constant. Thus, rate of change of flux through the windings will be
equal to zero. As a result, voltage at secondary will always be equal to 0.
2. An ideal transformer has infinite primary and secondary inductances.
a) True
b) False
View Answer
Answer: b
Explanation: The primary and secondary windings have zero resistance. It means that there is
no ohmic power loss and no resistive voltage drop in the ideal transformer. An actual
transformer has finite but small winding resistances.
3. In a transformer the resistance between its primary and secondary is ______________

a) Zero
b) Very small
c) Cannot be predicted
d) Infinite
View Answer
Answer: d
Explanation: Since the primary and secondary windings are not connected to each other, one
can say there exists the resistance of infinite ohms. These windings are connected to each
other magnetically not electrically.
4. Identify the correct statement relating to the ideal transformer.

a) no losses and magnetic leakage
b) interleaved primary and secondary windings
c) a common core for its primary and secondary windings
d) core of stainless steel and winding of pure copper metal
View Answer
Answer: a
Explanation: There is no leakage flux so that all the flux is confined to the core and links both
the windings. An actual transformer does have a small amount of leakage flux which can be
accounted in detailed analysis by appropriate circuit modelling.
5. An ideal transformer will have maximum efficiency at a load such that _____________
a) copper loss = iron loss
b) copper loss < iron loss
c) copper loss > iron loss
d) cannot be determined
View Answer
Answer: a
Explanation: Maximum efficiency of a transformer is defined at the that values when, copper
losses become completely equal to the iron losses. In all other cases the efficiency will be
lower than the maximum value.
6. Which of the following statement regarding an ideal single-phase transformer is incorrect?

Transformer is having a turn ratio of 1: 2 and drawing a current of 10 A from 200 V AC
supply is incorrect?
a) It’s a step-up transformer
b) Its secondary voltage is 400 V
c) Its rating is 2 kVA
d) Its secondary current is 20 A
View Answer
Answer: d
Explanation: Since turns ratio is equal to 1:2 the transformer will give higher voltage at
secondary with respect to the primary voltage, and current in secondary thus will be halved.
In last option current is doubled which is opposite to the ratings given.
7. Ideal transformer core has permeability equal to _____

a) Zero
b) Non-zero finite
c) Negative
d) Infinite
View Answer
Answer: d
Explanation: The core has infinite permeability so that zero magnetizing current is needed to
establish the requisite amount of flux in the core. The core-loss (hysteresis as well as eddy-
current loss) is considered zero.
8.Turns ratio of the transformer is directly proportional to ____________

a) Resistance ratio
b) Currents ratio
c) Voltage ratio
d) Not proportional to any terms
View Answer
Answer: c
Explanation: According to the voltage expression, emf induced in the primary is directly
proportional to the change in the flux with respect to the time and number of turns of the
primary winding. Similarly, for secondary winding.
9. Which of the following statement is correct regarding turns ratio?

a) Current ratio and turns ratio are inverse of each other
b) Current ratio is exactly same to the voltage ratio
c) Currents ratio is exactly same to the turns ratio
d) Voltage ratio and turns ratio are inverse of each other
View Answer
Answer: a
Explanation: Voltage ratio of transformer winding is exactly similar to the turns ratio of
transformer, while voltage ratio and turns ratio is exactly inverse of the currents ratio. Hence,
by knowing any of these quantities on can identify the type of transformer.
10. Which of the following is the expression for emf induced in primary with voltage applied
to primary of an ideal transformer?
a) e=V
b) V= √2*e*cos ωt
c) e= √2*V*cos ωt
d) Cannot say
View Answer
Answer: c
Explanation: For an ideal transformer having a primary of N1 turns and a secondary of N2
turns on a common magnetic core. The voltage of the source to which the primary is
connected is v = √2 V cos wt. while the secondary is initially assumed to be an open
circuited. As a consequence, flux f is established in the core such that e = v = N1 dφ/dt.
11. Which of the following is the wrong expression?

a) i1N1=i2N2
b) i1v1=i2v2
c) i1N2=i2N1
d) v2N1=v1N2
View Answer
Answer: c
Explanation: According to the transformation ratio, current flowing through the transformer
is inversely proportional to the number turns of winding and voltage applied across it. While,
voltage applied is directly proportional to the number of turns.
12. For transformer given, turns ratio is equal to a, what will be the impedance of primary
with respect to secondary?
a) a2 times the secondary impedance
b) a times secondary impedance
c) secondary impedance/a
d) secondary impedance/a2
View Answer
Answer: d
Explanation: The ratio of impedances on primary to the secondary is directly proportional to
the inverse of square of turns ratio of transformer. Hence primary impedance to the secondary
impedance ratio will be 1/ a2.
13. Power transformed in the ideal transformer with turns ratio a is _______
a) a2 times primary
b) a times primary
c) primary power/ a2
d) primary power
View Answer
Answer: d
Explanation: In an ideal transformer, voltages are transformed in the direct ratio of turns,
currents in the inverse ratio and impedances in the direct ratio squared; while power and VA
remain unaltered. Thus, primary power= secondary power.
14. For a transformer with primary turns 100, secondary turns 400, if 200 V is applied at
primary we will get ___________
a) 80 V at secondary
b) 800 V at secondary
c) 1600 V at secondary
d) 3200 V at secondary
View Answer
Answer: b
Explanation: Voltage in the primary of the transformer will get modified in the transformer
secondary, according to the number of turns. Thus, turns are modified with 4 times the
primary, we’ll get 4 times higher voltage at secondary.
15. For a transformer with primary turns 400, secondary turns 100, if 20A current is flowing
through primary, we will get ___________
a) 80A at secondary
b) 5A at secondary
c) 800A at secondary
d) 40A at secondary
View Answer
Answer: a
Explanation: Current in the primary of the transformer will get modified in the transformer
secondary, according to the number of turns, in inverse proportion. Thus, turns are modified
with 1/4 times the primary, we’ll get 4 times higher current at secondary.
1. If R is the resistance of secondary winding of an electrical transformer and K is the
transformation ratio then the equivalent secondary resistance referred to primary will be
_________
a) R/VK
b) R/K2
c) R2/K2
d) R2/K
View Answer
Answer: b
Explanation: Resistances or more precisely impedances are transformed in the ratio of inverse
square of the transformation ratio or turns ratio. Thus, primary to secondary resistance is
equal to reciprocal of square of turns ratio.
2. The use of higher flux density in the transformer design ________________

a) reduces weight per kVA
b) reduces iron losses
c) reduces copper losses
d) increases part load efficiency
View Answer
Answer: a
Explanation: If a material is having higher flux density it will store and transfer maximum
amount of flux from primary to secondary, which will be very helpful as less core material
will be required and weight per KVA will get reduced.
3. The value of flux involved in the emf equation of a transformer is _______________

a) average value
b) rms value
c) maximum value
d) instantaneous value
View Answer
Answer: c
Explanation: In the emf equation flux involved is maximum flux. Thus, here we can conclude
that as flux increase/decrease emf at the secondary also increases/decreases. Emf varies
according to the AC wave input.
4. Which winding of the transformer has less cross-sectional area?

a) Primary winding
b) Secondary winding
c) Low voltage winding
d) High voltage winding
View Answer
Answer: d
Explanation: Winding having less cross-sectional area may be primary or secondary winding.
For high voltage winding cross sectional area is less while for low voltage winding cross
sectional are is more, due to inverse proportionality.
5. In constant frequency (50 Hz) power transformers, approximate form is used with
___________
a) π equivalent model
b) T equivalent model
c) π and T equivalent both
d) Another model
View Answer
Answer: b
Explanation: In constant frequency (50 Hz) power transformers, approximate forms of the
exact T-circuit equivalent of the transformer are commonly used. Thus, we lump all series
parameters of the circuit on either side of T circuit.
6. Exciting current in an electrical transformer will not be affected much if primary is excited
with E rather than V.
a) True
b) False
View Answer
Answer: a
Explanation: Since winding resistances and leakage reactances are very small, V1 = E1 even
under conditions of load. Therefore, the exciting current drawn by the magnetizing branch
(Gi || Bm) would not be affected significantly by shifting it to the input terminals, i.e. it is
now excited by V1 instead of E1.
7. In approximate equivalent circuit of the transformer _______________

a) All resistances and inductances are lumped before magnetizing branch
b) All resistances and inductances are lumped after magnetizing branch
c) Resistances and inductances aren’t changed
d) Any of the above will work
View Answer
Answer: b
Explanation: Since Io is very small compare to like about 5-10% of full load current, voltage
drop can be approximated to very large extent. These all resistances and inductances are in
series, combined with each other to give approximate equivalent circuit.
8. Final approximate equivalent circuit contains _________

a) Only equivalent X series branch
b) Only equivalent Z series branch
c) Only equivalent R series branch
d) Any of the above
View Answer
Answer: a
Explanation: We combine all series parameters of equivalent circuit together to get
approximate equivalent circuit of the transformer, where we assume that equivalent resistance
is zero as it is negligible, and parallel branch is removed.
1. In a given transformer for given applied voltage, which of the following losses remain
constant irrespective of load changes?
a) Friction and windage losses
b) Copper losses
c) Hysteresis and eddy current losses
View Answer
Answer: c
Explanation: Hysteresis and eddy current losses together called as core-loss in a transformer.
These losses remain constant for constant voltage and frequency applied to a transformer,
these components remain same irrespective of load.
2. On which of the following degree of mechanical vibrations produced by the laminations of

a transformer depends?
a) Tightness of clamping
b) Gauge of laminations
c) Size of laminations
d) Tightness of clamping, gauge and size of laminations
View Answer
Answer: d
Explanation: Mechanical vibrations produced in a transformer are directly effective due to the
tightness of the clamping, gauge og laminations, size of laminations as well. There are
various methods in order to reduce their effects.
3. Variations in a hysteresis loss in a transformer (Bmax = maximum flux density)

____________
a) Bmax
b) Bmax1.6
c) Bmax3.83
d) Bmax/2
View Answer
Answer: b
Explanation: According to Steinmetz’s formula, the heat energy dissipated due to hysteresis
is given by Wh=ηβmax1.6, and hysteresis loss is thus given by Ph≈ Whf ≈ηfβmax1.6. That
exponetital term varies fraom 1.4 -1.8 and is equal to 1.6 for iron.
4. Leakage flux in the transformer depends on _____________________
a) Load current
b) Load current and voltage
c) Load current, voltage and frequency
d) Load current, voltage, frequency and power factor
View Answer
Answer: a
Explanation: Leakage flux is directly proportional to the current, as if is current increased net
value of flux increases thus, flux leakage also increases which further contribute to the losses
as it is then not able to link with secondary windings .
5. The full-load copper loss of a transformer is 1600 W. At half-load, the copper loss will be
_______
a) 6400 W
b) 1600 W
c) 800 W
d) 400 W
View Answer
Answer: d
Explanation: Copper losses are defined as I2*R losses many times, as they are directly
proportional to the square of current flowing through them. Thus, copper losses will reduce if
load is reduced that too in square proportion.
6. Silicon steel used in laminations, because it reduces ________________

a) Hysteresis loss
b) Eddy current losses
c) Copper losses
View Answer
Answer: a
Explanation: Electrical steels are also known as lamination steel or silicon steel. The main
special thing related to the silicon steel is, its magnetic properties such as small hysteresis
area and hence, small energy dissipation per cycle, thus low core loss.
7. If the supply frequency to the transformer is increased, the iron loss will ___________
a) Not change
b) Decrease
c) Increase
View Answer
Answer: c
Explanation: As frequency increases, the flux density in the core decreases but as the iron
loss is directly proportional to the frequency hence effect of increased frequency will be
reflected in increase of the iron losses.
8. Which of the following can measure iron loss of a transformer?

a) Low power factor wattmeter
b) Unity power factor wattmeter
c) Frequency meter
d) Any type of wattmeter
View Answer
Answer: a
Explanation: As the secondary side is open in OC, the entire coil will be purely inductive in
nature. So, the power will be lagging due to inductive property of the circuit. So LPF (Low
power factor) wattmeter is used in open circuit test of transformer.
9. How reduction in core losses and increase in permeability can be obtained simultaneously
in a transformer?
a) Core built-up of laminations of cold rolled grain oriented steel
b) Core built-up of laminations of hot rolled sheet
c) Cannot be determined
d) Frequency Meter
View Answer
Answer: a
Explanation: CRGO is supplied by the producing mills in coil form and has to be cut into
laminations, which are then used in transformer core, which is an integral part of any
transformer. Grain-oriented steel is used in large power, distribution transformers and in
certain audio output transformers also.
10. Losses which occur in rotating electric machines and do not occur in transformer are
______
a) Friction and windage losses
b) Magnetic losses
c) Hysteresis and eddy current losses
d) Copper losses
View Answer
Answer: a
Explanation: Windage and friction losses occur in rotating parts of a machine generally in
rotor of the machine, thus they will never occur in transformer, as transformer does not
contain any rotating part at its secondary unlike induction motor.
11. In a given transformer for a given applied voltage, which losses remain constant
irrespective of load changes?
a) Hysteresis and eddy current losses
b) Friction and windage losses
c) Copper losses
View Answer
Answer: a
Explanation: Hysteresis and eddy current losses are voltage and frequency dependent losses
that too from primary side thus, load change will not make any effect on these losses and they
will remain constant as long as voltage and frequency is constant.
12. Which of the following loss in a transformer is zero even at full load?
a) Core loss
b) Friction loss
c) Eddy current loss
d) Hysteresis loss
View Answer
Answer: b
Explanation: Friction losses are involved with rotating parts of a machine. Since in a
transformer all parts are stationary, friction losses will always be equal to zero, irrespective of
the loading condition.
13. A shell-type transformer has __________

a) High eddy current losses
b) Reduced magnetic leakage
c) Negligible hysteresis losses
View Answer
Answer: b
Explanation: Since windings are brought closer in shell type compare to core type
transformer, leakage of flux is very less in shell type transformer. Most of the flux gets linked
with both of the coils though there is some leakage which can’t be avoided.
. During open circuit test (OC) of a transformer _____________

a) primary is supplied rated kVA
b) primary is supplied full-load current
c) primary is supplied current at reduced voltage
d) primary is supplied rated voltage
View Answer
Answer: d
Explanation: Open circuit test is normally conducted on rated voltage because any machine is
constructed to give maximum efficiency near rated value. Hence, it is operated at rated
voltage, and we have to perform the test on machine is to be used.
2. Open circuit test on transformers is conducted so as to get ______________
a) Hysteresis losses
b) Copper losses
c) Core losses
d) Eddy current losses
View Answer
Answer: c
Explanation: Open circuit test gives the core losses also called as iron losses and shunt
parameters of the equivalent circuit of transformer. Open circuit test and short circuit test
both provide all the parameters of equivalent circuit.
3. Why OC test is performed on LV side?

a) Simple construction
b) Less voltage is required and parameters can be transformed to HV side
c) It’ll not give losses ig conducted on HV side
d) HV side does not have connections for voltage
View Answer
Answer: b
Explanation: Open circuit test can be performed on any side but for our convenience and
supply voltage available we generally conduct the test on LV side, to get corresponding
parameters on HV side we can use transformation ratio.
4. In OC test all the power supplied is utilised for ______

a) Core losses
b) Iron losses
c) Windage losses
View Answer
Answer: b
Explanation: In open circuit test all the power supplied is used to overcome iron losses and
hence, by taking the reading of input power one can easily do the calculations to find shunt
parameters of equivalent circuit of transformer.
5. How shunt branch component Gi is calculated?
a) Po/v12
b) V1/Io
c) Io/ V2
d) Any of the above
View Answer
Answer:
Explanation: Shunt branch resistance inverse is denoted by Gi. This Gi can be calculated by
the power drop taking place in the resistance divided by square of the voltage applied across
the resistor. Current by voltage will give net admittance.
6. Which of the following statements is/are correct statements?

a) EMF per turn in LV winding is more than EMF per turn in LV winding
b) EMF per turn in LV winding is less than EMF per turn in LV winding
c) EMF per turn in HV winding is equal to EMF per turn in LV winding
d) Can’t comment
View Answer
Answer: c
Explanation: In a transformer, primary volt-ampere is equal to secondary volt-ampere and
primary ampere turns are also equal to secondary ampere turns So, EMF per turn in both the
winding are equal. Total induced emf on both sides depends on the number of turns, flux and
frequency.
7. If the applied voltage of a transformer is increased by 50% and the frequency is reduced by
50%, the maximum flux density will _____________
a) Changes to three times the original value
b) Changes to 1.5 times the original value
c) Changes to 0.5 times the original value
d) Remains the same as the original value
View Answer
Answer: a
Explanation: Magnetic flux density α β/A. Magnetic flux φ α V/f. φ2/ φ1 = V2/V1 * f1/f2.
Since voltage is increased by 50%, V2 thus becomes 1.5 times V1 and frequency becomes
0.5 times the original frequency. Thus, maximum flux density changes to 3 times the original
value.
8. The total core loss can be termed as ____________

a) Eddy current loss
b) Hysteresis loss
c) Copper loss
d) Magnetic loss
View Answer
Answer: d
Explanation: The total core loss is due to iron core or any core material used. As iron loss is
proportional to magnetic flux density or flux, these are also called as magnetic loss. The total
core loss or magnetic loss in any given transformer totally consists of eddy current loss and
hysteresis loss.
9. 2 KVA, 230 V, 50 Hz single phase transformer has an eddy current loss of 40 watts. The
eddy current loss when the transformer is excited by a dc source of same voltage will be
___________
a) Equal to 40W
b) Less than 40W
c) More than 40W
d) Zero watts
View Answer
Answer: d
Explanation: Eddy current loss is directly proportional to the frequency^2. So, for DC current
frequency is equal to 0 Hz. Thus, eddy current losses being directly proportional to square of
frequency they’ll be equal to 0.
10. Which of the following is the correct formula for Bm?

a) Bm= (Yo2-Gi2)(1/2)
b) Bm= (Yo2+Gi2)(1/2)
c) Bm= (Yo2-Gi2)(2)
d) Bm= (Yo2+Gi2)(1/2)
View Answer
Answer: a
Explanation: We get the value of Y0 from the no-load current and voltage reading as, Io/V1.
Similalry we get the value of Gi from output power and voltage reading as, Po/V1. It then
follows that, Bm= (Yo2-Gi2)(0.5).
11. How shunt branch component Y0 is calculated?

a) I0/V1
b) V1/I0
c) P0/V12
View Answer
Answer: a
Explanation: Shunt branch admittance is defined as inverse of shunt branch impedance. As
we know, impedance can be calculated by the simple ohm’s law; admittance is equal to the
inverse of the impedance.
1. While conducting short-circuit test on a transformer which side is short circuited?

a) High voltage side
b) Low voltage side
c) Primary side
d) Secondary side
View Answer
Answer: b
Explanation: It’s a common practice to conduct SC test from HV side, while keeping LV side
short circuited. Thus, short circuited current is made to flow from shorted low voltage
terminals i.e. LV side.
2. During short circuit test why iron losses are negligible?
a) The current on secondary side is negligible
b) The voltage on secondary side does not vary
c) The voltage applied on primary side is low
d) Full-load current is not supplied to the transformer
View Answer
Answer: c
Explanation: Very small amount of voltage is given to the transformer primary thus the
magnetic losses which are dependent on magnetic flux density will get minimum value,
hence iron losses are negligible.
3. Short circuit test on transformers is conducted to determine ______

a) Core losses
b) Copper losses
c) Hysteresis losses
d) Eddy current losses
View Answer
Answer: b
Explanation: Short circuit test is used to determine the copper losses taking place in the
transformer under operation, while open circuit test gives us the value of core losses taking
place in the transformer.
4. When a short circuit test on a transformer is performed at 25 V, 50 Hz, the drawn current is
I1. If the test is performed by 25 V and 25 Hz and power drawn current is I2, then
a) I1 > I2
b) I1 < I2
c) I1 = I2
d) Can’t be defined
View Answer
Answer: b
Explanation: Current by ohm’s law is equal to voltage divided by impedance. So, I=V/Z.
Here Z is inductive load, thus Z= 2πfL. So as the frequency decreases the impedance also
decreases and ultimately it reduces the denominator term causing increase in current.
5. Why SC test is not conducted on LV side?

a) Difficult to arrange low voltage supply
b) Difficult to arrange high current supply
c) Difficult to arrange low voltage and high current supply to the LV
d) SC test on LV does not give correct results
View Answer
Answer: c
Explanation: If rated voltages and power is considered we need only 5% of rated voltage to
be applied at on HV side, while by calculations current requirement is also less. For the same
test on LV side though voltage required is less compare to HV side, current required is very
high.
6. SC test gives ______________

a) Series parameters of equivalent circuit
b) Parallel parameters of equivalent circuit
c) Both parameters of equivalent circuit
d) Neither series nor parallel parameter of equivalent circuit
View Answer
Answer: a
Explanation: Short circuit test gives the copper losses; these losses are taken into
consideration by series parameters of the equivalent circuit. While, Open circuit test gives us
iron losses; which are shown by parallel components of equivalent circuit.
7. For 200 kVA, 440/6600-V transformer, short circuit test on the LV side would require
______
a) 22V
b) 330V
c) 44V
d) Can’t be calculated
View Answer
Answer: a
Explanation: For a given transformer SC test is conducted on LV side, thus we’ll use 5% of
rated voltage on the low voltage side. Hence, 5% of 440V calculation gives the value of
440*5/100= 22V on LV side.
8. For a transformer given of 100 kVA, 220/6000-V transformer, short circuit test is
performed. What current rating is needed?
a) 30A
b) 445A
c) 60A
d) Can’t be calculated
View Answer
Answer: b
Explanation: For a given transformer here, test is performed on low voltage side, thus we
need the value of current on the low voltage side, by dividing the reactive power by the rated
voltage value, i.e. 200*1000/100= 445A.
9. What will be the value of voltage and current for a given transformer of 10 MVA,
220/4400-V which we are about to perform the Short circuit test?
a) 220 V, 30 A
b) 220 V, 2.27A
c) 440 V, 30 A
d) 440 V, 2.27 A
View Answer
Answer: b
Explanation: Since short circuit test is always done on the HV side unless mentioned
specifically, thus values are calculated with HV side parameters. Voltage required on HV
side = 4400*5/100 = 220 V and 10*1000/4400= 2.27A.
10. We only get copper losses from the short circuit test.
a) True
b) False
View Answer
Answer: a
Explanation: Since the transformer is excited at very low voltage, the iron-loss is negligible
(that is why shunt branch is left out), the power input corresponds only to the copper-loss, i.e.
PSC = PC (copper-loss).
11. With the help of short circuit calculations we get value of ____________
a) Individual resistance and inductance of both sides
b) Resistance and inductance of primary side
c) Resistance and inductance of primary side
d) Combined resistance and inductance of both sides
View Answer
Answer: d
Explanation: Short calculations include the ratio of short circuited voltage to the short-
circuited current which gives Z value, similarly the R value is calculated by dividing the
Short-circuited power with short circuited current square. Then, X is calculated for whole
circuit.
12. Short circuit test is performed on a transformer with a certain impressed voltage at rated
frequency. What will happen if the short circuit test is now performed with the same
magnitude of impressed voltage, but at frequency higher than the rated frequency?
a) The magnitude of current will increase, but power factor will decrease
b) The magnitude of current will decrease, but power factor will increase
c) The magnitude of current will increase, power factor will increase
d) The magnitude of current will decrease, power factor will decrease
View Answer
Answer: d
Explanation: Since frequency has been increased, the leakage reactance will increase. Which
will increase the impedance. Thus, current will be less due to inverse proportionality and
power factor will be poorer.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Three units of single phase transformers and one single three-phase transformer
rating
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) will be same for one rating

THIS IS
MANDATORY
OPTION
((OPTION_B)) can never be made same

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) may be same

This is optional
((OPTION_D)) none of the mentioned

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION Three single phase transformers and one single unit of three phase transformer
)) This is also will be same only. this is done to reduce the cost and spacing.
optional
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) The transformer which is more feasible to use in the distribution ends should be
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) star-delta
THIS IS
MANDATORY
OPTION
((OPTION_B)) delta-star
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Scott
This is optional
((OPTION_D)) delta-delta
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION Star-delta will have lower voltage at delta end.

)) This is also
optional
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) When does star/star transformers work satisfactorily?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Load is unbalanced only

THIS IS
MANDATORY
OPTION
((OPTION_B)) Load is balanced only

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) On balanced as well as unbalanced loads

This is optional
((OPTION_D)) Independent of load type

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION With the unbalanced load connected to the neutral, the neutral point shifts
)) This is also thereby making the three line-to-neutral (i.e. phase) voltages unequal. The
optional effect of unbalanced loads can be illustrated by placing a single load between
phase (or coil) a and the neutral on the secondary side.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) When does delta/star transformer work satisfactorily?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Load is balanced only

THIS IS
MANDATORY
OPTION
((OPTION_B)) Load is unbalanced only

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) On balanced as well as unbalanced loads

This is optional
((OPTION_D)) Independent of load type

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION Large unbalanced/balanced loads can be handled satisfactory. The Y-D

)) This is also connection has no problem with third harmonic components due to circulating
optional currents in D(delta). It is also more stable to unbalanced loads since the D
partially redistributes any imbalance that occurs.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Scott connections are used in _______________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) three-phase to single phase transformation

THIS IS
MANDATORY
OPTION
((OPTION_B)) three-phase to two-phase transformation

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) single phase to three-phase transformation

This is optional
((OPTION_D)) all phase transformations

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION Scott connections are used to convert three-phase to two-phase conversion, to

)) This is also start two phase motors and two phase furnaces. It requires two single phase
optional transformers with adjustable tappings, one transformer is main transformer
which is centre tapped through teaser transformer primary with a suitable
number of turns to get a balanced two-phase supply.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) In a three-phase star – delta transformer, what is the angle difference between
primary and secondary phase voltages?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Delta side leads by 30 degree

THIS IS
MANDATORY
OPTION
((OPTION_B)) Delta side lags by 30 degree

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Star side leads by 30 degree

This is optional
((OPTION_D)) Star side lags by 30 degree

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION This is a vector group and has + 30° displacement. Therefore, delta side leads by
)) This is also + 30°. So, it can be stated that delta side is having lead of 30 degree over star
optional side because of the connections made.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Open delta connection has VA rating of _______________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) √3 times delta/delta VA rating

THIS IS
MANDATORY
OPTION
((OPTION_B)) 1/√3 times delta/delta VA rating

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) 3 times delta/delta VA rating

This is optional
((OPTION_D)) 1/3 times delta/delta VA rating

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION When one of the transformer in delta/delta connection is removed we get open
)) This is also delta connection. This connection can handle the power of √3VI. While on the
optional similar line delta/delta connection can handle the power of 3VI.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) When star/star connection is used?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Small HV
THIS IS
MANDATORY
OPTION
((OPTION_B)) Small LV
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) High HV
This is optional
((OPTION_D)) High LV
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION This case is economical for small HV transformers as it minimizes the

)) This is also turns/phase and winding insulation. A neutral connection is possible. However,
optional the Y /Y connection is rarely used because of difficulties associated with the
exciting current.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) When delta/delta connection is used?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Small HV
THIS IS
MANDATORY
OPTION
((OPTION_B)) Small LV
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) High HV
This is optional
((OPTION_D)) High LV
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION This suits large LV transformers as it needs more turns/phase of smaller section.
)) This is also A large load unbalance can be tolerated. The absence of a star point may be a
optional disadvantage. This connection can operate at 58% normal rating as open-delta
when one of the transformers of the bank is removed for repairs or
maintenance.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) For using as a step-up transformer which connection is used?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Star/star
THIS IS
MANDATORY
OPTION
((OPTION_B)) Delta/delta
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Delta/star
This is optional
((OPTION_D)) Star/delta
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION This is the most commonly used connection for power systems. At transmission
)) This is also levels star connection is on the HV side, i.e. D/Y for step-up and Y/D for step-
optional down. The neutral thus available is used for grounding on the HV side.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) For two transformers connected in parallel, not having unequal percentage
impedances, which statement is correct?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Short-circuiting of the secondaries

THIS IS
MANDATORY
OPTION
((OPTION_B)) Power factor of one of the transformers is leading while that of the other lagging
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Transformers having higher copper losses will have negligible core losses
This is optional
((OPTION_D)) Loading of the transformers not in proportion to their kVA ratings

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH D
OICE)) Either A
or B or C or D or
E
((EXPLANATION In parallel operation of a transformer, loading gets divided between the whole
)) This is also set in proportion of their impedances. Thus, if impedances are not same then,
optional loading of transformers will not be in the ratio of their kVA ratings.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) For the parallel operation of two single phase transformers it is necessary that
they should have
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) same efficiency

THIS IS
MANDATORY
OPTION
((OPTION_B)) same polarity

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) same kVA rating

This is optional
((OPTION_D)) same number of turns on the secondary side

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION Polarity of the two transformers must be same if the are supposed to be
)) This is also operated in parallel mode of operation. It is okay if they have unequal
optional efficiencies, or unequal kVA ratings, as parallel connection is still possible.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Transformers operating in parallel mode of operation will share the load
depending upon their
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) leakage reactance

THIS IS
MANDATORY
OPTION
((OPTION_B)) per unit impedance

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) efficiencies
This is optional
((OPTION_D)) Ratings
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION In parallel operation of a transformer, loading of the transformers gets divided
)) This is also between the whole set in proportion of their per unit impedances. Thus, if per
optional unit impedances are not same then, loading will not be in the ratio of their kVA
ratings.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) What will happen if the transformers working in parallel are not connected with
regard to polarity?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) The power factor of the two trans-formers will be different from the power
factor of common load
THIS IS
MANDATORY
OPTION
((OPTION_B)) Incorrect polarity will result in dead short circuit

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) The transformers will not share load in proportion to their kVA ratings
This is optional

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION As far polarity is concerned, the transformers are connected in the same
)) This is also sequence when they are operated in parallel combination. An incorrect polarity
optional connection of these transformers will result in dead short circuit.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Y/Y and Y/D transformers can be paralleled.

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) True
THIS IS
MANDATORY
OPTION
((OPTION_B)) False
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C))
This is optional
((OPTION_D))
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D or
E
((EXPLANATION For example, Y/Y and Y/D transformers cannot be paralleled as their secondary
)) This is also voltages will have a phase difference of 30°. Transformers with +30° and –30°
optional phase shift can, however, be paralleled by reversing the phase-sequence of one
of them.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Why transformers connected in parallel should have same voltage ratio?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) To avoid full load circulating current

THIS IS
MANDATORY
OPTION
((OPTION_B)) To avoid no-load circulating current

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) To avoid other losses

This is optional
((OPTION_D)) To avoid all type of currents

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH B
OICE)) Either A
or B or C or D
or E
((EXPLANATION The transformers must have the same voltage-ratio to avoid no-load circulating
)) This is also current when transformers are in parallel on both primary and secondary sides.
optional Since the leakage impedance is low, even a small voltage difference can give rise
to considerable no-load circulating current and extra I2R loss.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Why transformers are paralleled?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Economical than replacing by one single large unit

THIS IS
MANDATORY
OPTION
((OPTION_B)) Less maintaining cost

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) To handle more load

This is optional
((OPTION_D)) Economical factors, more load capacity, less maintenance

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
D
((CORRECT_CH
OICE)) Either A
or B or C or D or
E
((EXPLANATION When the load outgrows the capacity of an existing transformer, it may be
)) This is also economical to install another one in parallel with it rather than replacing it with
optional a single larger unit. Also, sometimes in a new installation, two units in parallel,
though more expensive, may be preferred over a single unit for reasons of
reliability—half the load can be supplied with one unit out. Further, the cost of
maintaining a spare is less with two units in parallel.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) If two transformers’ secondaries are connected to each other with unequal
primary voltage ratio then, __________
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) no circulating current will flow

THIS IS
MANDATORY
OPTION
((OPTION_B)) very high short circuit current will flow

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) small circulating current will flow

This is optional
((OPTION_D)) insufficient information

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION When secondaries are paralleled by closing the switch, a circulating current
)) This is also appears even though the secondaries are not supplying any load, as a result of
optional difference in their voltage ratios.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) If the transformers have equal voltage ratio then, ____________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) exciting current can be neglected

THIS IS
MANDATORY
OPTION
((OPTION_B)) summation of two transformer currents is not equal to the net load current
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) difference of two transformer currents is equal to the net load current
This is optional
((OPTION_D)) current will not flow

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION When the transformers have equal voltage ratio, E1 = E2, the equivalent circuit
)) This is also of the two transformers would then be simple because of the assumption that
optional the exciting current can be neglected in comparison to the load current.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Individual currents are in two loaded transformers ______________

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) inversely proportional to the respective leakage impedances

THIS IS
MANDATORY
OPTION
((OPTION_B)) inversely proportional to the net leakage impedances

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) inversely proportional to another leakage impedance

This is optional
((OPTION_D)) directly proportional to the respective leakage impedances

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION the individual currents are inversely proportional to the respective leakage
)) This is also impedances. Thus, if the transformers are to divide the total load in proportion
optional to their kVA ratings, it is necessary that the leakage impedances be inversely
proportional to the respective kVA ratings.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Which of the following is the correct ratio, for transformers having equal voltage
ratios?
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) Z1/Z2= S2(rated)/ S1(rated)

THIS IS
MANDATORY
OPTION
((OPTION_B)) Z1/Z2= S1(rated)/ S2(rated)

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) Z1/Z2= I1(rated)/ I2(rated)

This is optional
((OPTION_D)) Depends upon the type of connection

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION If the transformers are to divide the total load in proportion to their kVA ratings,
)) This is also it is necessary that the leakage impedances be inversely proportional to the
optional respective kVA ratings. Thus, Z1/Z2= S2(rated)/ S1(rated) = VLI2/ VLI1. Hence, Z1/Z2=
I2/ I1.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Which of the following is the correct statement?

ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) SL(max)= S2(rated) Z1+Z2/Z2

THIS IS
MANDATORY
OPTION
((OPTION_B)) SL(max)= S1(rated) Z1+Z2/Z1

THIS IS ALSO
MANDATORY
OPTION
((OPTION_C)) SL(max)= S2(rated) Z1+Z2/Z1

This is optional
((OPTION_D)) SL(max)= S1(rated)+S2(rated)

This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH C
OICE)) Either A
or B or C or D or
E
((EXPLANATION We can define maximum load in kVA relating with rated kVA of transformer 1 as,
)) This is also S2(rated)= (Z1/Z2+Z1) *SL(max). Thus, by rearranging terms we get SL(max)=
optional S2(rated) Z1+Z2/Z1 and SL(max)= S1(rated) Z1+Z2/Z2.
((MARKS)) 1
QUESTION IS OF
HOW MANY
MARKS? (1 OR 2
OR 3 UPTO 10)
((QUESTION)) Three winding and two winding transformers work on same working principle.
ENTER
CONTENT. QTN
CAN HAVE
IMAGES ALSO
((OPTION_A)) True
THIS IS
MANDATORY
OPTION
((OPTION_B)) False
THIS IS ALSO
MANDATORY
OPTION
((OPTION_C))
This is optional
((OPTION_D))
This is optional
((OPTION_E))
This is optional.
If optional keep
empty so that
system will skip
this option
((CORRECT_CH A
OICE)) Either A
or B or C or D or
E
((EXPLANATION Both the transformers work on the same principle of electromagnetic induction.
)) This is also Transformers may be built with a third winding in addition to the primary and
optional secondary winding called the tertiary. There are various purposes which dictate
the use of a tertiary winding.
1. Which of the following is not a routine test for transformers?
a) Impedance test
b) Core insulation voltage test
c) Radio interference test
d) Polarity test
View Answer
Answer: c
Explanation: Impedance test is done on a transformer in order to check net impedance offered
by a transformer circuit at rated supply. Polarity test is also done before SC and OC test on
transformer. Core insulation is also checked before installations in such tests.
2. Which of the following is not required for transformer testing to get an accurate result?
a) Class 0.1 current transformer
b) Class 0.1 voltage transformer
c) High power factor wattmeter
d) Voltmeters
View Answer
Answer: c
Explanation: To obtain accurate results it is essential that low power factor wattmeter,
precision grade ammeters, voltmeters, and class 0.1 (see BS 3938 and 3941) current and
voltage transformers are used.
3. All the instruments needed for transformer testing should be tested within span of
____________
a) a month
b) 3 months
c) 6 months
d) 12 months
View Answer
Answer: d
Explanation: These instruments should be checked at intervals not exceeding 12 months to
ensure that the requisite accuracy is maintained. All these instruments are highly sensitive in
their operation, thus to maintain accuracy testing is essential.
4. Epstein square method is used in power transformer installations, to check ___________

a) Core frame insulation
b) Core-plate checks
c) Core-loss measurement
d) Winding copper checks
View Answer
Answer: a
Explanation: Incoming core plate is checked for thickness and quality of insulation coating. A
sample of the material is cut and built up into a small loop known as an Epstein Square from
which a measurement of specific loss is made. Such a procedure is described in BS 6404.
5. Generally Core frame insulation test is done at _________
a) 10 kV DC
b) 10 kV AC
c) 2KV RMS
d) 2KV DC
View Answer
Answer: c
Explanation: This is checked by Megger and by application of a 2 kV RMS or 3 kV DC test
voltage on completion of erection of the core. These checks are repeated following
replacement of the top yoke after fitting the windings.
6. Why tanks are tested?

a) Stiffness
b) Vacuum withstand capacity
c) Stiffness and vacuum withstand capacity
d) Any other purpose
View Answer
Answer: c
Explanation: The first tank of any new design should be checked for stiffness and vacuum-
withstand capability. For 275 and 400 kV transformers, a vacuum equivalent to 25 mbar
absolute pressure should be applied. This need only be held long enough to take the necessary
readings and verify that the vacuum is indeed being held, which might take up to 2 hours for
a large tank.
7. How much pressure is applied for transformers rated 132 kV and below ones?
a) 330 mbar
b) 300 mbar
c) 400 mbar
d) 500 mbar
View Answer
Answer: a
Explanation: For transformers rated 132 kV and below a more modest vacuum test equivalent
to 330 mbar absolute pressure should be applied. The permissible permanent deflections
following this test should be similar to those allowed for 275 and 400 kV transformer tanks
reduced pro-rata for smaller tanks.
8. Which of the following parameters don’t define that transformer is built correctly?
a) Losses
b) Polarity
c) Tap changing operation
d) Ratio
View Answer
Answer: a
Explanation: Tests to prove that the transformer has been built correctly: include ratio,
polarity, resistance, and tap change operation. While losses prove the that transformer is
guaranteed in its operation.
9. Which of the following parameters don’t define that transformer is built correctly?
a) Losses
b) Temperature rise
c) Noise level
d) Resistance
View Answer
Answer: d
Explanation: Tests to prove guarantees; these are losses, impedance, temperature rise, noise
level. While resistance, tap changing, ratio, polarity are the parts of tests that prove that
transformer has been built correctly.
10. Which of the following tests don’t indicate that transformer will work satisfactorily for at
least 30 Years?
a) Temperature rise
b) Dielectric test
c) Overvoltage test
d) Load current runs
View Answer
Answer: a
Explanation: Tests to prove that the transformer will be satisfactory in service for at least 30
years. The tests in this category are the most important and the most difficult to frame: they
include all the dielectric or overvoltage tests, and load current runs.
11. Which of the following is not in the category of special test for a transformer?
a) Short-circuit test
b) Harmonics on the no-load current
c) Power taken by fan and oil-pump motors
d) Open-circuit test
View Answer
Answer: d
Explanation: Special tests are tests, other than routine or type tests, agreed between
manufacturer and purchaser, for example: test with lightning impulse chopped on the tail,
zero-sequence impedance on three-phase transformers, and other tests included in options.
12. How temperature rise of an oil-immersed transformer is not found out?

a) Short circuit equivalent test
b) Delta/delta test
c) Back-to-back test
d) Normal SC test
View Answer
Answer: d
Explanation: When a test for temperature rise is specified it is necessary to measure the
temperature rise of the oil and the windings at continuous full load, and the various methods
of conducting this test are as follows: short-circuit equivalent test, back-to-back test,
delta/delta test, open-circuit test.
Which type of winding is used in 3-phase shell-type transformer?

a) Circular type
b) Sandwich type
c) Cylindrical type
d) Rectangular type
View Answer
Answer: b
Explanation: In core type of the transformer, winding is done by normal method, while in the
shell type transformer, winding is sandwiched between corresponding shells of core material.
Hence, it is sandwich type.
2. 3-phase transformers compare to 1-phase transformers ________

a) More economical
b) Easy in construction
c) Easy to construct
d) Easy to handle
View Answer
Answer: a
Explanation: 3-phase transformers are also used to power large motors and other heavy loads.
A three-wire three-phase circuit is more economical than an equivalent two-wire single-phase
circuit at the same line to ground voltage because it uses less conductor material to transmit a
given amount of electrical power.
3. How 3-phase transformers are constructed?

a) A bank of 3 single phase transformers
b) A single 3-phase transformer with the primary and secondary of each phase wound on
three legs of a common core
c) Single 3-phase transformer or a bank of 3 1-phase transformers
d) By different method
View Answer
Answer: c
Explanation: #-phase transformers can be either constructed by 2 methods. One is a bank of 3
single phase transformers and another method is a single 3-phase transformer with the
primary and secondary of each phase wound on three legs of a common core.
4. Three phase transformer compare to a bank of 3 single phase transformers is

____________
a) Cheaper
b) Costlier
c) More in space
d) Can’t be determined
View Answer
Answer: a
Explanation: 3-phase transformers can be manufactured by 2 methods. The three-phase
transformer unit costs about 15% less than that of a bank and furthermore, the single unit
occupies less space. There is little difference in reliability.
5. In mines we use _______________

a) a single unit of 3-phase transformer
b) a bank of 3 single phase transformers
c) use of 3-phase transformer is avoided
d) a single unit or a bank
View Answer
Answer: b
Explanation: It is cheaper to carry spare stock of a single-phase rather than a three-phase
transformer. In underground use (mines) a bank of single-phase units may be preferred as it is
easier to transport these units. The bank also offers the advantage of a de-rated open-delta
operation when one single-phase unit becomes inoperative.
6. In three phase bank phases are ___________________

a) the phases are electrically not connected and magnetically independent
b) the phases are electrically not connected and magnetically dependent
c) the phases are electrically connected and magnetically independent
d) the phases are electrically connected and magnetically dependent
View Answer
Answer: c
Explanation: The 3-phase load bank is constructed by so that all three phases are made to be
connected with together electrically. By the same time these banks form three magnetic
circuits which are independent.
7. Where the tappings are provided in a transformer?

a) At the phase end of LV side
b) At the phase end of HV side
c) At the neutral side end of the HV side
d) At the middle of HV side
View Answer
Answer: d
Explanation: Tappings are provided in order to maintain the terminal voltage across the loads
within the permissible specified limits with respect to load variations. Tappings can be
provided at phase end or neutral end of HV side. But to maintain magnetic symmetry
tappings are preferred in the middle of the winding only.
8. Tappings are on _____________

a) LV side of a transformer
b) HV side of transformer
c) Not on any side
d) On both sides
View Answer
Answer: b
Explanation: Generally, tappings are preferred on HV side, because the HV side is low
current-high voltage side, tap changer involves low current interruption and large variations
or small steps are possible due to more no of turns.
9. In core type 3-phase transformer flux path chooses how many paths to return?
a) 2
b) Single
c) 3
d) Many
View Answer
Answer: a
Explanation: Flux of each limb in core type uses the other two limbs for its return path with
the three-magnetic flux’s in the core generated by the line voltages differing in time-phase by
120 degrees. Thus, the flux in the core remains nearly sinusoidal, producing a sinusoidal
secondary supply voltage.
10. Why shell type 3-phase transformer is used in large power transforming applications?
a) Can be made with more height
b) Can be made with less height
c) More height and less height flexibility
d) Due to other reasons
View Answer
Answer: b
Explanation: The shell-type five-limb type three-phase transformer construction is heavier
and more expensive to build than the core-type. Five-limb cores are generally used for very
large power transformers as they can be made with reduced height.
11. A three-phase transformer generally has the three magnetic circuits interlaced.
a) True
b) False
View Answer
Answer: b
Explanation: A three-phase transformer generally has the three magnetic circuits which are
interlaced to give a uniform distribution of the dielectric flux between the high and low
voltage windings. The exception is a three-phase shell type transformer. In the shell type of
construction, even though the three cores are together, they are non-interlaced.
1. When does star/star transformers work satisfactorily?

a) Load is unbalanced only
b) Load is balanced only
c) On balanced as well as unbalanced loads
d) Independent of load type
View Answer
Answer: b
Explanation: With the unbalanced load connected to the neutral, the neutral point shifts
thereby making the three line-to-neutral (i.e. phase) voltages unequal. The effect of
unbalanced loads can be illustrated by placing a single load between phase (or coil) a and the
neutral on the secondary side.
2. When does delta/star transformer work satisfactorily?

a) Load is balanced only
b) Load is unbalanced only
c) On balanced as well as unbalanced loads
d) Independent of load type
View Answer
Answer: c
Explanation: Large unbalanced/balanced loads can be handled satisfactory. The Y-D
connection has no problem with third harmonic components due to circulating currents in
D(delta). It is also more stable to unbalanced loads since the D partially redistributes any
imbalance that occurs.
3. Scott connections are used in _______________

a) three-phase to single phase transformation
b) three-phase to two-phase transformation
c) single phase to three-phase transformation
d) all phase transformations
View Answer
Answer: b
Explanation: Scott connections are used to convert three-phase to two-phase conversion, to
start two phase motors and two phase furnaces. It requires two single phase transformers with
adjustable tappings, one transformer is main transformer which is centre tapped through
teaser transformer primary with a suitable number of turns to get a balanced two-phase
supply.
4. In a three-phase star – delta transformer, what is the angle difference between primary and
secondary phase voltages?
a) Delta side leads by 300
b) Delta side lags by 300
c) Star side leads by 300
d) Star side lags by 300
View Answer
Answer: a
Explanation: This is a vector group and has + 30° displacement. Therefore, delta side leads
by + 30°. So, it can be stated that delta side is having lead of 300 over star side because of the
connections made.
5. Which can be also called as 00 /1800 connection?
a) Star/star
b) Direct star
c) Delta/star
d) Star/delta
View Answer
Answer: a
Explanation: Star connection is formed on each side by connecting together phase winding
terminals. The voltages of the corresponding phases (and thus of the corresponding lines) are
in phase. This is known as the 0°-connection. If the winding terminals on secondary side are
reversed, the 180°-connection is obtained.
6. What is the ratio of transformation of star/star connection?

a) Phase transformation x:1, line transformation x:1
b) Phase transformation x:1, line transformation 2x:1
c) Phase transformation x:1, line transformation x/3:1
d) Can’t say
View Answer
Answer: a
Explanation: The phase transformation ratio is given as x:1, where x simply denotes the turns
ratio of a transformer given, thus, in the star/star connection we will get the same ratios, as at
a particular point, voltage reading on primary will be proportional to secondary with x.
7. Delta/delta connection is also called as ____________

a) 00-connection
b) 900-connection
c) 1800-connection
d) 00/1800-connection
View Answer
Answer: d
Explanation: Delta/delta connection is also called as 00-connection as seen from the phasor
diagram that primary and secondary line voltages are in phase with each other. By reversing
connection, we can get 1800 phase shift.
8. What is the ratio of transformation of delta/delta connection?

b) Phase transformation x:1, line transformation 2x:1
c) Phase transformation x:1, line transformation x/3:1
d) Can’t determine
View Answer
Answer: a
ratio of a transformer given, thus, in the delta/delta connection also similar to the star/star, we
will get the same ratios, as at a particular point, voltage reading on primary will be
proportional to secondary with x.
9. Open delta connection has VA rating of _______________
a) √3 times delta/delta VA rating
b) 1/√3 times delta/delta VA rating
c) 3 times delta/delta VA rating
d) 1/3 times delta/delta VA rating
View Answer
Answer: b
Explanation: When one of the transformer in delta/delta connection is removed we get open
delta connection. This connection can handle the power of √3VI. While on the similar line
delta/delta connection can handle the power of 3VI.
10. Star/delta connection is also called as ____________

a) 300-connection
b) 00-connection
c) -300-connection
d) 300/-300-connection
View Answer
Answer: d
Explanation: Star/delta connection is also called as +/-300-connection as seen from the
phasor diagram that primary and secondary line voltages are either ahead or below by 300
phases with each other. By reversing connection, we can get another condition phase shift.
11. What is the ratio of transformation of star/delta connection?

b) Phase transformation x:1, line transformation √3x:1
c) Phase transformation x:1, line transformation 3x:1
d) Can’t determine with information available
View Answer
Answer: a
ratio of a transformer given, thus, in the star/delta connection we will get the √3 factor in
ratios, as at a particular point, voltage reading on primary will be proportional to secondary
with √3x.
12. x/√3:1 ratio is obtained in ______________

a) Star/delta
b) Delta/star
c) Delta/delta
d) Star/star
View Answer
Answer: b
ratio of a transformer given, thus, in the star/delta connection we will get the 1/√3 factor in
ratios, as at a particular point, voltage reading on primary will be proportional to secondary
with 1/√3x.
13. Which both connections have the same line transformation ratios?
a) Star/star and delta/delta
b) Star/delta and delta/star
c) Star/zig-zag star and delta/zig-zag star
d) Star/star, delta/delta and star/delta, delta/star
View Answer
Answer: d
Explanation: Star/star and delta/delta both connections have phase transfer ratio of x:1 and
line transfer ratio also equal to x:1, while star/zig-zag star and delta/zig-zag star connections
have line transformation ratio equal to 2/√3x:1
1. For very high voltage transformers which connection is cheaper on primary side?
a) Star
b) Delta
c) Open delta
d) Can be star/ delta/ open delta
View Answer
Answer: a
Explanation: In star connection with earthed neutral, the maximum voltage of the phase
winding to ground is 1/√3 or 58% of the line voltage, while in delta connection this is equal
to the line voltage in case of earthing of one of the lines during a fault. Thus, star on HV side
is cheaper.
2. In which of the circuit given positive and negative sequence currents will flow in primary?
a) Star/delta
b) Star/star
c) Open delta/delta
d) Delta/delta
View Answer
Answer: d
Explanation: The only positive and negative sequence currents flow in the lines on the delta
side. This could also be achieved by star-connected primary provided the primary and
secondary star points are grounded. But this is not recommended on account of flow of
ground current for unbalanced secondary loads.
3. When star/star connection is used?

a) Small HV
b) Small LV
c) High HV
d) High LV
View Answer
Answer: a
Explanation: This case is economical for small HV transformers as it minimizes the
turns/phase and winding insulation. A neutral connection is possible. However, the Y /Y
connection is rarely used because of difficulties associated with the exciting current.
4. When delta/delta connection is used?

a) Small HV
b) Small LV
c) High HV
d) High LV
View Answer
Answer: d
Explanation: This suits large LV transformers as it needs more turns/phase of smaller section.
A large load unbalance can be tolerated. The absence of a star point may be a disadvantage.
This connection can operate at 58% normal rating as open-delta when one of the transformers
of the bank is removed for repairs or maintenance.
5. For using as a step-up transformer which connection is used?

a) Star/star
b) Delta/delta
c) Delta/star
d) Star/delta
View Answer
Answer: c
Explanation: This is the most commonly used connection for power systems. At transmission
levels star connection is on the HV side, i.e. D/Y for step-up and Y/D for step-down. The
neutral thus available is used for grounding on the HV side.
6. At distribution level transformer with which connection is used?

a) Star/star
b) Delta/delta
c) Delta/star
d) Star/delta
View Answer
Answer: c
Explanation: At the distribution level the D/Y transformer is used with star on the LV side
which allows mixed 3-phase and 1-phase loads, while delta allows the flow of circulating
current to compensate for neutral current on the star side.
7. Third-harmonic currents have phase difference of _____________

a) 00
b) 900
c) 1800
d) 270
View Answer
Answer: a
Explanation: The phase difference in third-harmonic currents and voltages on a 3-phase
system is 3 * 120° = 360° or 0° which means that these are cophasal. Therefore, third-
harmonic currents and voltages cannot be present on the lines of a 3-phase system as these do
not add up to zero.
8. Core flux in the transformer is _______________

a) sinusoidal
b) flat-topped
c) square wave
d) triangular
View Answer
Answer: b
Explanation: The supply voltage provides the input current to the transformer primary, here
primary current is only sinusoidal magnetizing current. Thus, this sinusoidal magnetic current
will produce core flux, flat-topped.
9. In delta/delta connection flux is almost _________________

a) sinusoidal
b) flat-topped
c) triangular
d) square wave
View Answer
Answer: a
Explanation: The supply voltage provides only sinusoidal magnetizing current so that core
flux is flat-topped; but the third-harmonic emfs induced (cophasal) cause circulating currents
in deltas restoring the flux to almost sinusoidal.
10. Apart from connection which of the following is different in star/delta or delta/star
compare to delta/delta?
a) Flux is flat-topped
b) Impedance offered to third-harmonic currents in delta is less
c) Impedance offered to third-harmonic currents in delta is constant
d) Impedance offered to third-harmonic currents in delta is more
View Answer
Answer: d
Explanation: Because of one delta connection the same conditions are obtained as in D/D
connection except that the impedance offered to the flow of third-harmonic currents in delta
is now larger and so are third-harmonic voltages.
11. In star/star connection the voltage can be correctly expressed as ____________

a) eaN = ea sin 2ωt + ea3 sin 3ωt
b) eaN = ea sin ωt + ea3sin 3ωt
c) eaN = ea sin 3ωt + ea3sin 3ωt
d) eaN = ea sin 6ωt + ea3sin 3ωt
View Answer
Answer: b
Explanation: In the case of isolated neutrals, third-harmonic voltages are present in each
phase as explained earlier. Further, since these voltages are cophasal, no third-harmonic
voltages are present between lines. The voltage of phase a to neutral can now be expressed as
shown in option b.
12. Rate of change of voltage in star/star connection is ______________

a) ω
b) 2 ω
c) 3 ω
d) Can’t determine
View Answer
Answer: b
Explanation: While fundamental frequency voltages in the three phases have a relative phase
difference of 120°, the third-harmonic voltages in them are cophasal (with respect to each
other), but their phase with respect to the fundamental frequency (voltage changes at the rate
of 2ω, twice the fundamental frequency).
13. Voltage at the neutral point oscillates at frequency of 2ω, this phenomenon is called as
_________
a) oscillating neutral
b) doubling voltage
c) doubling current
d) doubling neutral
View Answer
Answer: a
Explanation: Voltage of the neutral point oscillates at frequency 2 ω, phenomenon is known
as oscillating neutral and is highly undesirable because of which the star/star connection with
isolated neutrals is not used in practice. If the neutrals are connected, it effectively separates
the three transformers. Third-harmonic currents can now flow via the neutrals
1. For two transformers connected in parallel, not having unequal percentage impedances,
which statement is correct?
a) Short-circuiting of the secondaries
b) Power factor of one of the transformers is leading while that of the other lagging
c) Transformers having higher copper losses will have negligible core losses
d) Loading of the transformers not in proportion to their kVA ratings
View Answer
Answer: d
Explanation: In parallel operation of a transformer, loading gets divided between the whole
set in proportion of their impedances. Thus, if impedances are not same then, loading of
transformers will not be in the ratio of their kVA ratings.
2. For the parallel operation of two single phase transformers it is necessary that they should
have ________
a) same efficiency
b) same polarity
c) same kVA rating
d) same number of turns on the secondary side
View Answer
Answer: b
Explanation: Polarity of the two transformers must be same if the are supposed to be operated
in parallel mode of operation. It is okay if they have unequal efficiencies, or unequal kVA
ratings, as parallel connection is still possible.
3. Transformers operating in parallel mode of operation will share the load depending upon
their ___________
a) leakage reactance
b) per unit impedance
c) efficiencies
d) ratings
View Answer
Answer: b
Explanation: In parallel operation of a transformer, loading of the transformers gets divided
between the whole set in proportion of their per unit impedances. Thus, if per unit
impedances are not same then, loading will not be in the ratio of their kVA ratings.
4. What will happen if the transformers working in parallel are not connected with regard to
polarity?
a) The power factor of the two trans-formers will be different from the power factor of
common load
b) Incorrect polarity will result in dead short circuit
c) The transformers will not share load in proportion to their kVA ratings
View Answer
Answer: b
Explanation: As far polarity is concerned, the transformers are connected in the same
sequence when they are operated in parallel combination. An incorrect polarity connection of
these transformers will result in dead short circuit.
5. If the percentage impedances of the two transformers working in parallel are different, then
______________________
a) transformers will be overheated
b) power factors of both the transformers will be same
c) parallel operation will be not possible
d) parallel operation will still be possible, but the power factors at which the two transformers
operate will be different from the power factor of the common load
View Answer
Answer: d
Explanation: If the percentage impedances of the two transformers which are working in the
parallel are different, then parallel operation is still possible, but load sharing will not be in
the ratio of their kVA loads.
6. A delta/star transformer is connected in parallel to a star/delta transformer. The turn ratio
former is x times latter, the x is _________
a) 3
b) 1/3
c) √3
d) 1/√3
View Answer
Answer: a
Explanation: Turn ratio of star1/ Turn ratio of delta 1= Vph/Vph/√3= √3
Ture ratio of star 2 / Turn ratio of delta 2= Vph/√3/Vph= 1/√3
Thus, turn ratio of star1/delta1 = 3 * turn ratio of star 2/ delta 2.
7. While connecting two transformers in parallel voltage around the local loop _________
a) positive
b) negative
c) equals zero
d) insufficient information
View Answer
Answer: c
Explanation: The transformers must be connected properly as far as their polarities are
concerned so that the net voltage around the local loop is zero. A wrong polarity connection
results in a dead short circuit.
8. For three phase power transformers relative phase displacement should be ____________
a) 00
b) 300
c) 900
d) 1800
View Answer
Answer: a
Explanation: Three-phase transformers must have zero relative phase displacement on the
secondary sides and must be connected in a proper phase sequence. Only the transformers of
the same phase group can be paralleled.
9. Y/Y and Y/D transformers can be paralleled.

a) True
b) False
View Answer
Answer: b
Explanation: For example, Y/Y and Y/D transformers cannot be paralleled as their secondary
voltages will have a phase difference of 30°. Transformers with +30° and –30° phase shift
can, however, be paralleled by reversing the phase-sequence of one of them.
10. Why transformers connected in parallel should have same voltage ratio?
a) To avoid full load circulating current
b) To avoid no-load circulating current
c) To avoid other losses
d) To avoid all type of currents
View Answer
Answer: b
Explanation: The transformers must have the same voltage-ratio to avoid no-load circulating
current when transformers are in parallel on both primary and secondary sides. Since the
leakage impedance is low, even a small voltage difference can give rise to considerable no-
load circulating current and extra I2R loss.
11. Why transformers are paralleled?

a) Economical than replacing by one single large unit
b) Less maintaining cost
c) To handle more load
d) Economical factors, more load capacity, less maintenance
View Answer
Answer: d
Explanation: When the load outgrows the capacity of an existing transformer, it may be
economical to install another one in parallel with it rather than replacing it with a single
larger unit. Also, sometimes in a new installation, two units in parallel, though more
expensive, may be preferred over a single unit for reasons of reliability—half the load can be
supplied with one unit out. Further, the cost of maintaining a spare is less with two units in
parallel.
1. If the primary voltages at two transformers V1 and V2 are not equal then on load, we’ll get
____________
a) V1-V2 at secondary
b) E1-E2 at secondary
c) V1+V2 at secondary
d) E1+E2 at secondary
View Answer
Answer: b
Explanation: When two transformers paralleled on both sides with proper polarities but on
no-load. The primary voltages V1 and V2 are obviously equal. If the voltage-ratio of the two
transformers are not identical, the secondary induced emfs, E11and E2 though in phase will
not be equal in magnitude and the difference (E1-E2) will appear across the switch S.
2. If two transformers’ secondaries are connected to each other with unequal primary voltage
ratio then, __________
a) no circulating current will flow
b) very high short circuit current will flow
c) small circulating current will flow
d) insufficient information
View Answer
Answer: c
Explanation: When secondaries are paralleled by closing the switch, a circulating current
appears even though the secondaries are not supplying any load, as a result of difference in
their voltage ratios.
3. The circulating current flowing through the circuit at no load condition depends on
________________
a) total leakage impedance of the two transformers
b) difference in their voltage ratios
c) difference in voltage ratios, leakage impedance of 2 transformers
d) other parameters
View Answer
Answer: c
Explanation: The circulating current flowing at no-load condition depend upon the total
leakage impedance of the two transformers and the difference in their voltage ratios. Only a
small difference in the voltage-ratios can be tolerated.
4. If the transformers have equal voltage ratio then, ____________

a) exciting current can be neglected
b) summation of two transformer currents is not equal to the net load current
c) difference of two transformer currents is equal to the net load current
d) current will not flow
View Answer
Answer: a
Explanation: When the transformers have equal voltage ratio, E1 = E2, the equivalent circuit
of the two transformers would then be simple because of the assumption that the exciting
current can be neglected in comparison to the load current.
5. Which is the correct formula for current flowing through the transformer 1, when they’re
having equal voltage ratio?
a) I1= Z2/(Z1+Z2) *IL
b) I2= Z2/(Z1+Z2) *IL
c) I1= Z1/(Z1+Z2) *IL
d) I1= Z2/(Z1-Z2) *IL
View Answer
Answer: a
Explanation: Since both the transformers are having same number of turns and thus equal
voltage ratios, it is easier for analysis of current as division in two branches will be according
to the Ohm’s law, which is the answer.
6. Individual currents are in two loaded transformers ______________

a) inversely proportional to the respective leakage impedances
b) inversely proportional to the net leakage impedances
c) inversely proportional to another leakage impedance
d) directly proportional to the respective leakage impedances
View Answer
Answer: a
Explanation: the individual currents are inversely proportional to the respective leakage
impedances. Thus, if the transformers are to divide the total load in proportion to their kVA
ratings, it is necessary that the leakage impedances be inversely proportional to the respective
kVA ratings.
7. Which of the following is the correct ratio, for transformers having equal voltage ratios?
a) Z1/Z2= S2(rated)/ S1(rated)
b) Z1/Z2= S1(rated)/ S2(rated)
c) Z1/Z2= I1(rated)/ I2(rated)
d) Depends upon the type of connection
View Answer
Answer: a
Explanation: If the transformers are to divide the total load in proportion to their kVA ratings,
it is necessary that the leakage impedances be inversely proportional to the respective kVA
ratings. Thus, Z1/Z2= S2(rated)/ S1(rated) = VLI2/ VLI1. Hence, Z1/Z2= I2/ I1.
8. Which of the following is the correct statement?

a) SL(max)= S2(rated) Z1+Z2/Z2
b) SL(max)= S1(rated) Z1+Z2/Z1
c) SL(max)= S2(rated) Z1+Z2/Z1
d) SL(max)= S1(rated)+S2(rated)
View Answer
Answer: c
Explanation: We can define maximum load in kVA relating with rated kVA of transformer 1
as, S2(rated)= (Z1/Z2+Z1) *SL(max). Thus, by rearranging terms we get SL(max)= S2(rated)
Z1+Z2/Z1 and SL(max)= S1(rated) Z1+Z2/Z2.
9. Maximum load kVA is _____________________

a) greater than addition of individual rated kVAs
b) lesser than addition of individual rated kVAs
c) equal to addition of individual rated kVAs
d) depends on the loading condition
View Answer
Answer: b
Explanation: As SL(max)= S2(rated) Z1+Z2/Z1 and SL(max)= S1(rated) Z1+Z2/Z2, because of
individual leakage impedances are inversely proportional to the respective kVA ratings.
Important thing is in either of the above cases maximum kVA loading is lesser than the
addition of both rated kVAs.
10. Which is the correct formula of current flowing through one of the transformers having
unequal ratios?
a) I2= E2Z1-(E1-E2) ZL / (Z1Z2 + ZL(Z1+Z2))
b) I1= E2Z1+(E1+E2) ZL / (Z1Z2 + ZL(Z1+Z2))
c) I1= E2Z1-(E1-E2) ZL / (Z1Z2 – ZL(Z1-Z2))
d) I2= E2Z1+(E1-E2) ZL / (Z1Z2 + ZL(Z1+Z2))
View Answer
Answer: a
Explanation: We know that a small difference in voltage ratios can be tolerated in the parallel
operation of transformers. Thus, in the unequal voltage ratio condition current will flow from
depending on both of the options stated above.
11. A 600-kVA, single-phase transformer with 0.012 pu resistance and 0.06 pu reactance is
connected in parallel with a 300-kVA transformer with 0.014 pu resistance and 0.045 pu
reactance to share a load of 800 kVA at 0.8 pf lagging. Find how they share the load (a) when
both the secondary voltages are 440 V.
a) S1= 377+j305.2
b) S2= 377-j305.2
c) S1= 264+ j171.6
d) S1= 377-j305.2
View Answer
Answer: d
Explanation: Z1= 0.012+j 0.06
Z2= 2(0.014+j0.045)
Z1+Z2= 0.04+ j0.15
The load is SL = 800(0.8-0.6j)
Thus, S1= Z2/Z1+Z2 SL, we get S1= 377- j305.2
S2 = Z1/Z1+Z2 SL, we get S2= 264-j171.
1. Three winding and two winding transformers work on same working principle.
a) True
b) False
View Answer
Answer: a
Explanation: Both the transformers work on the same principle of electromagnetic induction.
Transformers may be built with a third winding in addition to the primary and secondary
winding called the tertiary. There are various purposes which dictate the use of a tertiary
winding.
2. Why tertiary winding is used?

a) To make circuit stable
b) To provide voltage supply to the substations different from the primary and secondary
voltage levels
c) To connect static capacitors for reactive power injection
d) Stable circuit, different voltage output, static capacitor connection
View Answer
Answer: d
Explanation: Tertiary winding can be used to supply the substation auxiliaries at a voltage
different from those of the primary and secondary windings. Static capacitors or synchronous
condensers may be connected to the tertiary winding of a transformer for reactive power
injection into the system for voltage control.
3. Tertiary winding is generally _________
a) star connected
b) delta connected
c) open-delta connected
d) star or open-delta connected
View Answer
Answer: b
Explanation: Tertiary winding of the three-winding transformer is generally delta connected
which is helpful in reducing the impedance offered to the zero sequence currents thus, it
allows a larger earth-fault current to flow for proper operation of protective equipment.
4. Tertiary winding allows the flow of _______________

a) third harmonic currents
b) fifth harmonic currents
c) seventh harmonic currents
d) eleventh harmonic currents
View Answer
Answer: a
Explanation: Delta-connected tertiary winding limits voltage imbalance when the load is
unbalanced. It also permits the third harmonic current to flow which ultimately reduces third-
harmonic voltage. Thus, performs as a stabilizing winding to the transformer.
5. Tertiary winding can be used for ____________

a) to maximize the core area
b) to measure voltage during HV testing of transformer
c) to fill up the space between primary and secondary windings
d) to measure voltage during open circuit testing of transformer
View Answer
Answer: b
Explanation: There are many uses of tertiary winding, such as, three windings may be used
for interconnecting three transmission lines at different voltages. Tertiary winding can serve
the purpose of measuring voltage of an HV testing transformer.
6. Any unbalanced load can be divided into _______________

a) positive and negative sequence components
b) positive, negative and zero sequence components
c) only in positive and zero sequence components
d) only in negative and zero sequence components
View Answer
Answer: b
Explanation: Any unbalanced load can be divided into three 3-phase sets (positive, negative
and zero sequence components). The zero-sequence component (co-phasal currents on three
lines, I0 = In/3) caused by a line-to-neutral load on the secondary side cannot be balanced by
primary currents as the zero-sequence currents cannot flow in the isolated neutral star
connected primary.
7. Which currents flow through the delta-connected tertiary winding?
a) Positive sequence currents
b) Negative sequence currents
c) Zero sequence currents
d) All sequence currents
View Answer
Answer: c
Explanation: Iron path is available for the zero-sequence flux in a bank of single-phase units
and in the 5-limb core and as a consequence the impedance offered to the zero-sequence
currents is very high (0.5 to 5 pu) inhibiting the flow of these currents. The provision of a
delta-connected tertiary permits the circulation of zero-sequence currents in it, thereby
considerably reducing the zero-sequence impedance.
8. Simple phase equivalent circuit of three winding transformer can be shown as

____________
a) simple star network
b) simple parallel network
c) simple series network
d) can be shown accordingly
View Answer
Answer: a
Explanation: Particular winding can be represented as equivalent resistor and reactance. For
simplicity, the effect of the exciting current can be ignored in the equivalent circuit. It may be
noted that the load division between the secondary and tertiary is completely arbitrary.
9. How impedance of particular winding can be calculated?

a) Z1= Z12+Z13+Z23
b) Z1= 1/2½ (Z12+Z13-Z23)
c) Z1= Z12-Z13+Z23
d) Z1= Z12+Z13-Z23
View Answer
Answer: c
Explanation: The single-phase equivalent of three-winding transformer can be shown.
According to the short circuit test one can easily find the short circuit impedance between
winding 1 and 2 as Z12 and thus, formula for primary impedance can be calculated.
1. Only Scott connection is used for _________

a) Converting three-phase to two-phase conversion
b) Converting three-phase to single-phase conversion
c) Converting single-phase to two-phase conversion
d) None of the mentioned
View Answer
Answer: a
Explanation: Scott connection is used for obtaining two-phase supply as it is needed for
various special purposes like supplying two-phase electric arc furnaces and can easily
obtained from three-phase supply by this method.
2. In Scott connection, according to the vector diagram two windings are placed at
______________
a) At 1200 to each other
b) Perpendicular with respect to each other
c) At 600 to each other
d) Can’t say
View Answer
Answer: b
Explanation: For a transformer vector diagram, if one winding is kept along the perpendicular
axis of another winding then one can obtain two-phase supply from three-phase supply by
using Scott connection. Physically this can be obtained by appropriate turns ratio.
3. What is the ratio of voltage/turn of two windings of a transformer in operated in Scott

connection?
a) ½
b) 1/√2
c) 1
d) 1/√3
View Answer
Answer: c
Explanation: The transformer primaries must have √3 N1/2 (teaser) and N1 turns; this would
mean equal voltage/turn in each transformer. A balanced 2-phase supply could then be easily
obtained by having both secondaries with equal number of turns, N2.
4. The primaries of two transformers in Scott connection are in turns ratio of ___________
a) √3/2: 1
b) 2/√3: √2
c) 1:1
d) Can’t say
View Answer
Answer: a
Explanation: A 2-phase supply could thus be obtained by means of transformers; one
connected perpendicular according to the vector diagram is called the teaser transformer and
the other is connected across, with turns ratio √3/2: 1 respectively.
5. The secondaries of two transformers are in ratio ____

a) 1:1
b) √3/2: 1
c) √3: 1
d) √2: 1
View Answer
Answer: a
Explanation: Though transformer primaries are in the ratio of √3/2: 1 with respect to each
other secondary windings of these transformers are in ratio of 1:1. This simply means that
both of these transformers have equal voltage per turns.
6. In Scott connection neutral point is located at _______________

a) Three phase side at teaser
b) Two-phase side
c) Three phase side secondary
d) Anywhere
View Answer
Scanned by CamScanner
Id
Question Which of the following motor has the constant speed?
A Series motor
B Shunt motor
C Induction Motor
D All of the above
Answer B
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Question A DC series motor is best suitable for driving-----
A Machine tools
B Shears and punches
C Cranes and hoists
D Lathes
Answer C
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Question In a DC series motor increasing the load current will-------
A Increase the speed
B Decrease the speed
C Achieve better commutation
D Increase the back emf
Answer B
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Question The DC motor, which can provide low speed variation at full load without any
controller is -------
A Series motor
B Shunt motor
C Both of the above
D None of the above
Answer B
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Question The d.c. series motor should always be started with load because______
A it will not develop high starting torque
B at no load, it will rotate at dangerously high speed
C it will fail to start
D all are true
Answer B
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Question The speed of a d. c series motor at no load is-------------
A zero
B very low
C dangerously high
D can’t be said
Answer C
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Question The direction of rotation of a dc series motor can be reversed----------
A by interchanging the supply terminals
B by interchanging the field terminals
C by interchanging the supply or field terminals
D none of the above
Answer B
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Question If a dc motor is connected across an ac supply, the dc motor will-----------
A run at a lower speed
B run at its normal speed
C burn as the eddy currents in the field produces heat
D can’t be said
Answer C
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Question If the field of a dc shunt motor is suddenly opened, _____________.
A it will run at its normal speed.
B the speed of the motor will be reduced.
C the motor will come to hault.
D the speed will be enormously high, and the motor will destroy itself.
Answer D
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Question Which one of the following motors is used in an electric locomotive?
A Squirrel Cage Induction motor
B DC series motor
C DC shunt motor
D None of the above
Answer B
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Question The armature torque of the dc shunt motor is proportional to------
A armature current only
B field flux only
C armature current and field flux both
D none of the above
Answer C
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Question The output power of any electrical motor is taken from the--------
A Motor frame
B Coupling mounted on the shaft
C Field
D Armature
Answer B
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Question If the back emf in a dc motor is reduced to zero, then the motor------
A start hunting
B come to hault
C may eventually burn
D Can't say
Answer C
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Question The direction of the armature current in a dc motor is--------------
A independent of the direction of the armature emf
B the same as the generated emf
C opposite to that of generated emf
D none of the above
Answer C
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Question The direction of rotation of a dc motor can be principally determined by---------
A Right hand thumb rule
B Fleming's right hand rule
C Fleming's left hand rule
D Ampere's law
Answer C
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Question A thick wire is used in dc series motor field winding than that of field winding of dc
shunt motor to_______________.
A To carry large load current
B To reduce the resistance
C To create more flux
D Both (A) and (B)
Answer D
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Question An electric train employing a dc series motor is running at the fixed speed. When a
sudden slight drop in the mains voltage occurs, this would result in-------------------
A Rise in the speed and drop in the current
B Rise in the speed and rise in the current
C Drop in the speed and rise in the current
D Drop in speed with current unaltered
Answer C
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Question A DC shunt motor is driving a constant torque load. On inserting an additional
resistance in the armature circuit, the speed of the motor will---------------
A be zero
B remain unchanged
C increase
D decrease
Answer D
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Question A DC series motor is best suited for driving cranes and hoists because-----------
A it is rugged in construction like induction motor
B it is cheaper in cost
C it develops high starting torque
D it runs at very high speed
Answer C
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A
B
C
D
Answer
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Question In a DC motor, unidirectional torque is produced with the help of________
A The speed of a dc motor can be controlled by varying_________

B flux per pole
C resistance of armature circuit
D applied voltage
Answer all of the above
Marks D
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Question The counter emf in a dc motor__________.
A Regulates its armature voltage
B Aids the applied voltage
C Often exceeds the supply voltage
D Helps in energy conversion
Answer D
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Question The Eb/V ratio of a dc motor is an indication of its------------
A Starting torque
B Running Torque
C Speed regulation
D Efficiency
Answer D
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Question The Ta/Ia graph of a dc series motor is a___________ .
A Straight line throughout
B Parabola throughout
C Parabola from no load to overload
D Parabola upto full load and a straight line at overloads
Answer D
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Question When load is removed, .......motor will run at the highest speed.
A Slip ring Induction motor
B Squirrel cage Induction motor
C Shunt
D Series
Answer D
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Question In a d.c. series motor, the electromagnetic torque developed is proportional to_______.
A Ia
B I 2a
C I 3a
D √a
Answer B
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Question A drawback of a dc series motor is its---------
A high starting torque
B low starting torque
C constant speed
D speed runaway
Answer D
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Question The speed of a d.c. motor may be increased by__________.
A decreasing the applied voltage
B increasing the armature current
C decreasing the field current
D increasing the field current
Answer C
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Question The effect of inserting a resistance in series with the field winding of a shunt motor is
to__________.
A increase the magnetic field

B increase the speed of the motor
C reduce the magnetic field
D decrease the speed of the motor
Answer B
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Question In a dc shunt motor; the terminal voltage is halved while the torque is kept constant.
The resulting approximate variation in speed 'N' and armature current ' Ia ' will be
____
A N is constant but Ia is halved.
B N is doubled while Ia is halved.

C N is constant and Ia is doubled.
D Both N and Ia are doubled.

Answer C
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Question The torque in a _____________is proportional to the square of the armature current.
A DC shunt motor
B DC series motor
C Separetely excited motor
D Squirrel cage induction motor
Answer B
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Question As compared to shunt DC motors, the series DC motor will have the highest torque
because of its comparatively ____________ at the start.
A Lower armature resistance.
B Fewer series turns.
C Larger armature current.
D Stronger series field.
Answer C
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Question Machine tools are a typical example of____________.
A Variable torque load
B Constant torque load
C Constant power load
D Both (B) and (C)
Answer D
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Question What would be observed if a d.c. shunt motor is started with an open-circuited field?
A The motor does not pick up speed but draws a small current
B The motor does not pick up speed but draws is large current
C The motor pick up fast and acquires full speed while drawing small current
D The motor picks up fast and acquires full speed while drawing large current
Answer B
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Question Which of the following d.c. motors has approximately constant speed?
A series motor
B shunt motor
C Induction motor
D all of the above
Answer B
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Question If the supply voltage in a shunt motor is increased, which of the following will be
decreased?
A starting torque
B full load speed
C full load current
D none of the above
Answer D
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Question If a d.c. series motor is started at no load, it will_________.
A not start
B start at nominal speed
C run at very high r.p.m.
D run with.excessive noise
Answer C
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Question What is the function of commutator of the d.c. motor?
A To produce unidirectional torque
B to converts alternating emf induced into DC voltage
C to improve efficiency of machine
D to obtain high starting torque
Answer B
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Question A d.c. shunt motor is running at light load. If the field winding gets suddenly opened,
what will happen?
A motor will stop instantly.
B motor will tend to pick up high speed.
C motor will take heavy input current.
D motor will make mechanical noise.
Answer B
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Question A d.c. series motor__________
A may stop if the field gets opened.
B is not suitable for high starting torque.
C should always be started on load.
D always runs at constant speed.
Answer C
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Question Which of the following components is an identity of a d.c. motor?
A armature
B slip rings
C commutator
D field winding
Answer C
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Question A series motor has________.
A widely varying speed.
B high speed at high loads and low speed at low loads.
C approximately constant speed at all loads.
D both (A) and (B)
Answer A
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Question The motor used in centrifugal and reciprocating pumps is --------
A D.C series
B D.C. shunt
C Induction Motor
D None of the above
Answer B
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Question -----------is preferably used for speed control of DC shunt motor to obtain speed below
rated speed.
A Flux contolmethod
B Rheostatic control method
C Applied voltage control method
D Both (B) and (C)
Answer B
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Question Tapped field method is used for controlling speed of -------------
A D.C. shunt motor
B D.C. series motor
C Squirrel cage induction motor
D Slip ring induction motor
Answer B
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Question Which of the following applications requires high starting torque ?
A Air blower
B Locomotive
C Lathe machine
D Centrifugal pump
Answer B
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Question Which type of D.C. motor will be preferred for machine tools ?
A Squirrel cage induction motor
B Slip ring induction motor
C Shunt motor
D Series motor
Answer C
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Question Starters are used for D.C. motors because____________.
A these motors are not self-starting.
B these motors have high starting torque.
C large armature current at start requires to be reduced.
D inertia at start is to be overcome.
Answer C
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Question In DC shunt motor as load is reduced,_____________
A the speed will be drastically reduced.
B the speed will be abruptly increased.
C the speed practically remains constant.
D can not be said
Answer C
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Question In case of DC shunt motors the speed is dependent on back e.m.f. only because ..........
A armature drop is negligible.
B back e.m.f. is equal to armature drop.
C flux is practically constant in these motors.
D flux is proportional to armature current.
Answer C
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Question A three point starter is considered suitable for ________.
A DC shunt motor
B DC series motor
C Slip ring induction motors
D Squirrrel cage induction motor
Answer A
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Question Although back emf opposes the applied voltage, it______________.
A increases the motor torque
B cannot equal the applied voltage
C decreases motor speed
D helps flow of armature current
Answer B
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Question Induced back emf in a dc motor acts as _________ regulator.
A current
B voltage
C efficiency
D torque
Answer A
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Question As load is applied to a dc shunt motor, its_____________.
A torque developed decreases
B counter emf increases
C armature current increases
D field current increases
Answer C
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Question When a dc series motor runs at high speed,___________.
A its armature current is small
B it develops less torque
C its Eb is large
D all of the above
Answer D
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Question The armature current drawn by a dc motor is given by I a= V / R aonly when the
motor..................
A runs at full load
B runs at half load
C is stationary
D none of the above
Answer C
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Question The armature power developed by a dc motor_____________.
A V Ia
B Eb I a
C I 2a Ra
D All of the above
Answer B
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Question Condition for maximum power developed by a dc motor is_____________.
A E b =V
B E b =V /2
C E b >V
D E b <V
Answer B
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Question As load is applied to a dc series motor, the_____________.
A Counter emf increases
B Armature current increases
C Series field current decreases
D Armature current decreases
Answer B
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Question Which of the following motor develops the highest torque between no load and full
load?
A Squirrel cage induction motor
B Slip ring induction motor
C Series motor
D Shunt motor
Answer D
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Question The armature torque developed by a dc shunt motor____________.
A decreases with increasing load
B directly depends on applied voltage
C varies directly with armature current
D is independent of speed
Answer C
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Question Which of the following dc motor is well suited for operating line shafts?
A Compound motor
B Separately excited motor
C Series motor
D Shunt motor
Answer D
Marks
Unit
Id
Question Because of its high starting torque, a series motor is used for___________.
A large presses
B centrifugal pumps
C machine tools
D electric trains
Answer D
Marks
Unit
Id
Question DC series motor is best suited for______________.
A lathe machines
B rapid transit systems
C drilling machines
D blowers
Answer B
Marks
Unit
Id
Question Motor starters are essential for____________.
A preventing fuse blowing
B starting the motor
C accelerating the motor
D avoiding the excessive starting current
Answer D
Marks
Unit
Id
Question For the same rating, DC_________motor has the highest starting torque.
A shunt
B compound
C Both (A) & (B)
D series
Answer D
Marks
Unit
Id
Question A dc motor is still used in industrial applications because it_____________.
A is cheap
B is simple in construction
C provides fine speed control
D requires low maintenance
Answer C
Marks
Unit
Id
Question The value of back emf in a dc motor is maximum at_____________.
A no load
B full load
C half full load
D at start
Answer A
Marks
Unit
Id
Question The running speed of a dc series motor is basically determined by___________.
A armature resistance
B field excitation
C load
D none of above
Answer C
Marks
Unit
Id
Question The deciding factor in the selection of a dc motor for a particular application is
its___________characteristics.
A speed--torque
B speed-- armature current
C torque-- armature current
D none of above
Answer A
Marks
Unit
Id
Question For the same rating, _________motor has the least starting torque.
A DC compound
B DC shunt
C DC series
D data insufficient
Answer B
Marks
Unit
Id
Question The only disadvantage of field control method for controlling the speed of a dc shunt
method is that it_____________.
A adversely affects commutation
B gives speed lower than the normal speed
C involves power loss
D needs a large rheostat
Answer A
Marks
Unit
Id
Question By flux control method of speed control of dc shunt motor, we can obtain speeds.........
A below the normal speed only
B above the normal speed only
C above as well as below the normal speed
D based upon applications requirement
Answer B
Marks
Unit
Id
Question The rheostatic speed control method is very___________.
A efficient
B economical
C unsuitable for rapidly changing loads
D suitable for getting speeds above the normal
Answer C
Marks
Unit
Id
Question By putting controller resistance in series with the armature of a dc motor, we can
obtain speeds.....................
A above the normal speed only
B below the normal speed only
C above as well as below the normal speed
D based on applications requirement
Answer B
Marks
Unit
Id
Question A 220 V dc shunt motor develops a torque of 54 N-m at an armature current of 0 A.
The torque produced when the armature current becomes 20 A is__________.
A 27 N-m
B 54 N-m
C 08 N-m
D None of these
Answer C
Marks 2
Unit
Id
Question A 220 V dc shunt motor has an armature resistance of 0.2 ohm and field resitance of 0
ohm. The motor draws 5 A at 500 rpm at no load. The speed when the motor draws 52
A at rated voltage is___________.
A 563.9 rpm
B 500 rpm
C 435.73 rpm
D None of these
Answer C
Marks 2
Unit
Id
Question A 250 V dc shunt motor runs at 000 rpm at no load and takes 8 A. The total armature
and shunt field resitances are 0.2 ohm and 250 ohm respectively. The motor will run
at________rpm while taking 50 A at rated voltage.
A 033.4 rpm
B 966.2 rpm
C 000 rpm
D None of these
Answer B
Marks 2
Unit
Id
Question A 460 V dc series motor runs at 500 rpm taking a current of 40 A. If now the load is
reduced and the motor takes 30 A, the percentage change in armature torque
is___________.
A 25.00%
B 33.33%
C 43.75%
D None of these
Answer C
Marks 2
Unit
Id
Question A 220 V shunt machine has an armature resistance of 0.5 ohm. If the full load armature
current is 20 A,the induced emfs when the machine acts as (i) motor and (ii) generator
are_______, __________respectively.
A 230 V, 20 V
B 20 V, 230 V
C 220 V, 220 V
D 220V, 230 V
Answer B
Marks 2
Unit
Id
Question A 440 V, shunt motor has armature resistance of 0.8 ohm and field resistance of 200
ohm. The armature current while delivering an output of 7.46 KW at 85 percent
efficiency is________.
A 4.75 A
B 9.95 A
C 7.75 A
D 22.5 A
Answer C
Marks 2
Unit
Id
Question A 250 V, dc shunt motor has armature and field resistances of 0.06 ohm and 00 ohm
respectively. The total armature power developed while taking 25 KW input
is________.
A 24.79 KW
B 26.25 KW
C 25.2 KW
D 23.8 KW
Answer D
Marks 2
Unit
Id
Question The load current of a d.c. series motor is 50 A, when supplying of a full load torque. If
the current is reduced to 25 A, the torque will be_________.
A same as full load torque

B 50% of full load torque
C 25% of full load torque
D can not be decided
Answer C
Marks 2
Unit
Id
Question A d.c. shunt motor runs at no load speed of 40 r.p.m. At full load, armature reaction
weakens the main flux by 5% whereas the armature circuit voltage drops by 0%. The
motor full load speed in r.p.m. is____________
A 000
B 080
C 200
D 203
Answer B
Marks 2
Unit
Id
Question A separately excited dc motor takes an armature current of 0 A at 480 V. The aramture
circuit resistance is 0.2 ohm. The machine has 6 poles and the aramture is lap
connected with 864 conductors. The flux per pole is 0.05 Wb. The operating speed of
the motor is_________.
A 697 rpm
B 232 rpm
C 636 rpm
D None of these
Answer C
Marks 2
Unit
Id
Question A dc shunt motor develops a counter emf of 250 V at 500 rpm. The aramture torque
developed while drawing 50 A armature current is_____________.
A .32 N-m
B .99 N-m
C 79.58 N-m
D None of these
Answer C
Marks 2
Unit
Id
Question The developed torque of a 220 V, 4-pole series motor with wave wound 800
conductors; taking 45A from mains is___________.The flux per pole is 25 mWb.
A 94.53 N-m
B 43. N-m
C 286.2 N-m
D None of these
Answer C
Marks 2
Unit
Id
Question A 220 V dc shunt motor runs at 500 rpm when the armature current is 50 A for given
load. The armature resistance is 0.2 ohm. The speed when the torque is doubled
is...............
A 476 rpm
B 490 rpm
C 50 rpm
D None of the above
Answer A
Marks 2
Unit
Electrical Machine 1
Unit 5 & 6 Three Phase Induction Motors
MCQ Questions
Q.1 Choose correct relation between rotor copper loss ( W cu )and gap power ( P g ) of three phase
IM.
a) W cu =s . P g
b) Pg
W cu =
S
c) W cu = s2 . P g
d) W cu =( 1 − s )∗ P g
Q.2 Choose correct relation between mechanical power developed ( P md) and gap power ( P g )
of three phase IM.
a) P md =( s )∗P g
b) P md = s2∗P g
c) P md =( 1− s )∗ P g
d) P
P md = g
S
Q.3 Induction motor efficiency is

a) P
η= g
Pi
b) P sh
η=
Pi
c) P
η= md
Pi
d) P
η= sh
P md
Q.4 The condition for maximum torque in IM is

a) R 2=S X 20
b) R 2 R 2=¿ 91−¿= X ¿
20
c) R 2= s 2 X 20
d) R 2=(1−S)∗X 20
Q.5 Which of the following statement is correct in case of construction of three phase IM?
a) Stator is stationary part.
b) A three phase AC supply is given to rotor
c) A three phase AC supply is given to stator
d) Both a) and c)
Mmcoe SE Electrical
1
Q.6 The main function of stator frame is

a) To support stator core and field winding
b) It acts as covering and provide protection to rotor
c) It gives mechanical strength to all inner parts of IM.
d) All of the above
Q.7 The winding wound on three phase IM is called as…..

a) Rotor winding
b) Frame winding
c) Field winding
d) Core winding
Q.8 The difference between synchronous speed and speed of rotor is called as…..
a) Slip
b) Slip speed
c) Rotor speed
d) Filed speed
Q.9 In case of IM, which one is true relation between synchronous speed and speed of rotor?
a) N S =N r
b) N S < N r
c) N S ≈ N r
d) N S > N r
Q.10 When motor is at rest condition, slip is

a) 1
b) -1
c) 0
d) Equal to synchronous speed
Q.11 The correct relation between synchronous speed and speed of rotor is
a) N S =(1−S ) N r
b) N r =(1 − S ) N S
c) N r = S∗ N S
d) N S =N r
Q.12 A three phase, 4 pole, 440 V, 50 Hz IM runs with slip 4%. Find rotor speed N r .
a) N r =1440
b) N r =1500
c) N r =60
d) N r =18750
Q.13 A three phase, 4 pole, 440 V, 50 Hz IM runs with slip 4%. Find frequency of rotor current
.
a) frequency of rotor current = 4 Hz.
Mmcoe SE Electrical
2
b) frequency of rotor current = 2Hz.

c) frequency of rotor current¿ 1 Hz .
d) frequency of rotor current¿ 50 Hz .
Q.14 A 6 pole IM is connected to 50 Hz supply. It is running at a speed of 970 rpm. Find

synchronous speed
a) N S =1000
b) N S =1500
c) N S =1455
d) N S =970
Q.15 Rotor of three phase IM is usually made up of

a) Copper
b) Carbon
c) Aluminum
d) Cast Iron
Q.16 A 4-pole three-phase induction motor has a synchronous speed of 25 rev/s. The frequency
of the supply to the stator is:
a) 50
b) 100
c) 25
d) 12.5
Q.17 In induction motor the unit of slip is

a) rpm
b) Meter per second
c) Unit less
d) radian
Q.18 A three phase, 4 pole, 50 Hz star connected IM running on full load has mechanical
power developed ( P md) is 52778.552 W. Find gap power ( P g ). The rotor speed is 1440
rpm.
a) P g =54977.86 W
b) P g =60000 W
c) P g =52278.552 W
d) P g =2199.114 W
Q.19 A three phase, 4 pole, 50 Hz star connected IM running on full load has mechanical
power developed ( P md ) is 52778.552 W. rotor copper loss (W cu ). The rotor speed is 1440
rpm.
a) W cu =54977.86 W
b) W cu =60000 W
c) W cu =52278.552 W
d) W cu = 2199.114 W
Mmcoe SE Electrical
3
Q.20 With the increase in supply voltage, the starting torque of a 3 phase induction motor
a) decreases
b) Remains same
c) increases.
d) None of above
Q.21 The shaft of an induction motor is made of

a) high speed steel
b) stainless steel
c) carbon steel
d) cast iron
Q.22 In an induction motor, no-load the slip is generally

a) less than 1%
b) 1.5%
c) 2%
d) 4%
Q.23 In medium sized induction motors, the slip is generally around

a) 0.04%
b) 0.4%
c) 4%
d) 14%
Q.24 In a squirrel cage motor the induced e.m.f. is

a) dependent on the shaft loading
b) dependent on the number of slots
c) slip times the stand still e.m.f. induced in the rotor
d) none of the above
Q.25 For driving high inertia loads best type of induction motor suggested is
a) Slip ring type
b) squirrel cage type
c) any of the above
Q.26 What will happen if the relative speed between the rotating flux of stator and rotor of the
induction motor is zero ?
a) The slip of the motor will be 5%
b) The rotor will not run
c) The rotor will run at very high speed
d) The torque produced will be very large
Q.27 The torque of a rotor in an induction motor under running condition is maximum
a) at the unit value of slip
Mmcoe SE Electrical
4
b) at the zero value of slip

c) at the value of the slip which makes rotor reactance per phase equal to the
resistance per phase
d) at the value of the slip which makes the rotor reactance half of the rotor
Q.28 Slip rings are usually made of

a) copper
b) carbon
c) phospor bronze
d) aluminium
Q.29 A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor e.m.f. will
be
a) 200 Hz
b) 50 Hz
c) 2 Hz
d) 0.2 Hz
Q.30 The efficiency of an induction motor can be expected to be nearly

a) 60 to 90%
b) 80 to 90%
c) 95 to 98%
d) 99%
Q.31 The number of slip rings on a squirrel cage induction motor is usually
a) two
b) three
c) four
d) Zero
Q.32 The starting torque of a squirrel-cage induction motor is

a) low
b) same as full-load torque
c) negligible
d) slightly more than full-load torque
Q.33 Star-delta starting of motors is not possible in case of

a) single phase motors
b) variable speed motors
c) low horse power motors
d) high speed motors
Q.34 In case of the induction motors the torque is

a) inversely proportional to (V*slip)
b) directly proportional to (slip)2
c) inversely proportional to slip
Mmcoe SE Electrical
5
d) directly proportional to slip
Q.35 Which of the following methods is easily applicable to control the speed of the squirrel-
cage induction motor ?
a) By changing the number of stator poles
b) Rotor rheostat control
c) By operating two motors in cascade
d) By injecting e.m.f. in the rotor circuit
Q.36 Rotor resistance control method of speed control is used for

a) squirrel-cage induction motors only
b) slip ring induction motors only
c) both (a) and (b)
Q.37 An induction motor is

a) self-starting with zero torque
b) self-starting with high torque
c) self-starting with low torque
d) non-self-starting
Q.38 The maximum torque in an induction motor depends on

a) frequency
b) rotor inductive reactance
c) square of supply voltage
d) all of the above
Q.39 In three-phase squirrel-cage induction motors

a) rotor conductor ends are short-circuited through slip rings
b) rotor conductors are short-circuited through end rings
c) rotor conductors are kept open
d) rotor conductors are connected to insulation
Q.40 DOL starting of induction motors is usually restricted to

a) low horsepower motors
b) variable speed motors
c) high horsepower motors
d) high speed motors
Q.41 In an induction motor the relationship between stator slots and rotor slots is that
a) stator slots are equal to rotor slots
b) stator slots are exact multiple of rotor slots
c) stator slots are not exact multiple of rotor slots
Q.42 Slip ring motor is recommended where
Mmcoe SE Electrical
6
a) speed control is required

b) frequent starting, stopping and reversing is required
c) high starting torque is needed
d) all above features are required
Q.43 If a 3-phase supply is given to the stator and rotor is short circuited rotor will move
a) In the opposite direction as the direction of the rotating field
b) in the same direction as the direction of the field
c) in any direction depending upon phase sequence of supply
d) none
Q.44 The speed characteristics of an induction motor closely resemble the speed load
characteristics of which of the following machines
a) D.C. series motor
b) D.C. shunt motor
c) universal motor
Q.45 A 3-phase slip ring motor has

a) double cage rotor
b) wound rotor
c) short-circuited rotor
d) any of the above
Q.46 The starting torque of a 3-phase squirrel cage induction motor is

a) twice the full load torque
b) 1.5 times the full load torque
c) equal to full load torque
d) Half to full load torque
Q.47 In a three-phase induction motor

a) iron losses in stator will be negligible as compared to that in rotor
b) iron losses in motor will be neg¬ligible as compared to that in rotor
c) iron losses in stator will be less than that in rotor
d) iron losses in stator will be more than that in rotor
Q.48 The shape of the torque/slip curve of induction motor is

a) parabola
b) hyperbola
c) rectangular parabola
d) straigth line
Q.49 The frame of an induction motor is usually made of

a) silicon steel
b) Cast iron
c) aluminium
Mmcoe SE Electrical
7
d) bronze
Q.50 Which of the following component is usually fabricated out of silicon steel ?
a) Bearings
b) Shaft
c) Stator core
d) All of the above
Q.51 A 500 kW, 3-phase, 440 volts, 50 Hz, A.C. induction motor has a speed of 960 r.p.m. on
full load. The machine has 6 poles. The slip of the machine will be
a) 0.01
b) 0.02
c) 0.03
d) 0.04
Q.52 What will happen if the relative speed between the rotating flux of stator and rotor of the
induction motor is zero ?
a) The slip of the motor will be 5%
b) The rotor will not run
c) The rotor will run at very high speed
d) The torque produced will be very large
Mmcoe SE Electrical
8
MCQ PowerSy
stem 1
Uni
t4
Ski
nEf
fectCauses-MCQswi
thAnswer
s
Q1.Onwhatf
act
orsdoest
heski
nef
fectdependupon?
a.
Cr osssect i
onoftheconductors.
b.Supplyfrequency.
c.
Per meabi l
i
tyoftheconductor.
d.Allofthese.
ANSWER:
d.Al
loft
hese.
Q2.Whatar
ethel
ineconst
ant
sinat
ransmi
ssi
onl
ine?
a.
Resistanceandseri
esconductanceonly.
b.Seri
esandshuntconductance.
c.
Resistance,
induct
anceandcapacitance.
d.Resi
stance,i
nduct
ance,capaci
tanceandshuntconduct
ance.
ANSWER:
d.Resi
stance,
induct
ance,
capaci
tanceandshunt
conduct
ance.Q3.Whati
sthecauseofski
nef
fect
?
a.
Supplyf r
equency.
b.Selfi
nductanceofconduct
or.
c.
Hi ghsensit
ivemater
iali
nthecent
re.
d.Both(a)and(b)
ANSWER:
d.Bot
h(a)and(
b)
Q4.Theconduct
orcar
ri
esmor ecur
rentont
hesur
facei
ncompar
isont
oit
scor
e.
Whatist
hisphenomenoncal
led?
a.
Corona
b.
Ferrant
ieff
ect.
c.
Skineff
ect.
d.
Proximit
yeffect
.
ANSWER:
c.Ski
nef
fect
.
Q5.Byusi
ngwhi
chconduct
ori
stheski
nef
fectr
educed?
a.
Bundl
edconductors.
b.
Str
andedconductors.
c.
Hol
lowconduct
ors.
d.
Sol
i
dconductor
s.
ANSWER:
b.St
randedconduct
ors.
Q6.I
nwhi
choft
het
ransmi
ssi
onsy
stemsi
stheski
nef
fectobser
ved?
a.
Cablecar
ryingdccur r
ent
.
b.DCtr
ansmissionl
ineonly.
c.
ACtransmissionl
i
neonl y.
d.DCaswellasACt ransmi
ssionl
i
nes.
ANSWER:
c.ACt
ransmi
ssi
onl
ineonl
y.
Q7.Ski
nef
fecti
naconduct
ori
spr
opor
ti
onalt
o
1/
2
a.(
Di ameterofconduct
or)
b.Diameterofconductor.
2
c.(
Di ameterofconduct
or)
4
d.(Diameterofconductor
)
2
ANSWER:
c.(
Diamet
erofconduct
or)
Q8.Ski
nef
fecti
snegl
igi
blef
orwhatsuppl
yfr
equencyandf
orwhatdi
amet
er?
a.
<50Hzand<1cm.
b.
<50Hzand>1cm.
c.
>50Hzand<1cm.
d.
>50Hzand>1cm.
ANSWER:
a.<50Hzand<1cm.
Pr
oxi
mit
yEf
fect-MCQswi
thAnswer
s
Q1.Thecur
rentdi
str
ibut
ionmaynotbeuni
for
minaconduct
or,
whi
chef
fecti
sthi
s?
a.
Skineffect.
b.Pr
oximityeffect
.
c.
Ferrant
i eff
ect.
d.Noneoft hese.
ANSWER:
b.Pr
oxi
mit
yef
fect
.
Q2.Pr
oxi
mit
yef
fect
a.
Ismor einlar
geconduct or
s,hi
ghfrequency
b.
Increasestheresi
stanceoftheconductor
c.
Reducest heselfr
eactance.
d.
Allofthese.
ANSWER:
d.Al
loft
hese.
Li
neI
nductanceofasi
ngl
ephaseci
rcui
t-MCQs
wi
thAnswers
Q1.Whati
sthet
otalr
esi
stancei
nasi
ngl
ephaseor2–wi
redcl
ine?
a.
Equaltotheresistanceofeit
herconductor.
b.Doubl
etheresistanceofeit
herconductor.
c.
Halfoftheresi
stanceofeitherconduct
or .
d.Noneofthese.
ANSWER:
b.Doubl
ether
esi
stanceofei
therconduct
or.
Q2.Thei
nduct
anceofasi
ngl
ephaset
wowi
repowert
ransmi
ssi
onl
ineperkm get
s
doubl
edwhen
a.
Dist
ancebetweenthewir
esisdoubl ed.
b.
Dist
ancebetweenthewir
esincreasedfour
fold.
c.
Dist
ancebetweenthewir
esisincreasedasthesquar
eoft
heor
igi
nal
dist
ance.
d.
Radiusoft
hewi r
eisdoubl
ed.
ANSWER: c.Di
stancebet
weent
hewi
resi
sincr
easedast
hesquar
eoft
heor
igi
nal
di
stance
Q3.Induct
anceofasi
ngl
ephaset
wopar al
lelwi
retr
ansmi
ssi
onl
inehav
ingconduct
or
r
adi
usrandspacingDbet
weenconduct
orsisequalto
a.2π*10-7l
nD/r
-
7
b.4*10 lnD/r
c.4π*10-7l
nD/r
-
7
d.2*10 lnD/r
b.4*10-7l
ANSWER: nD/r
Q5.Theconduct
orofa15km long,
singl
ephasetwowi
rel
inearesepar
atedbya
dist
anceof1.
5m.Thedi amet
erofeachconduct
ori
s1cm.Ift
heconductorsar
eof
copper,
thei
nductanceoft
hecir
cui
tis
a.23.
81mH
b.35.
72mH
c.32.
81mH
d.53.
72mH
ANSWER:
b.35.
72mH
Q6.Thei
nduct
anceofat
ransmi
ssi
onl
inei
smi
nimum when
a.
GMDi shigh.
b.GMRishigh.
c.
BothGMDandGMRarehi
gh.
d.GMDislowandGMRi
shi
gh.
ANSWER:
d.GMDi
slowandGMRi
shi
gh.
Q7.Asingl
ephasel
inehast
woparal
lelconduct
ors2met reapart
.Thediamet
erof
eachconduct
ori
s1.2cm.Whati
stheloopinductanceperkm ofthel
ine?
a.2.
423mH
b.1.
234mH
c.3.
267mH
d.8.
632mH
ANSWER:
a.2.
423mH
Li
neI
nductanceofat
hreephaseci
rcui
t-MCQs
wi
thAnswers
Q1.At hr
eephase, 50Hztr
ansmissi
onli
neconsi
stsofthr
eeequalconductorsofradii‘
r’
pl
acedinahor i
zontalpl
anewithaspaci
ngof6m betweenmiddl
eandout erconductor.
I
ftheradiusofeachconductori
s12.5mm,theninduct
anceperphaseperkm ofthe
tr
ansposedli
newi l
lbe
a.
1.33mH/km
b.
1.65mH/km
c.
0.38mH/km
d.
2.145mH/km
ANSWER:
a.1.
33mH/
km
Q3.Athreephasetransmissi
onli
nehasitsconductor
satthecorner
sofan
equi
lat
eralt
riangl
ewithsides3m.Thediameterofeachconduct
oris1.
63cm.What
i
stheinductanceoftheli
neperphase?
a.1.
232mH
b.1.
184mH
c.2.
236mH
d.2.
68mH
ANSWER:
a.1.
232mH
Q4.Whatwil
lbet
heinductanceofeachconductori
nat hr
eephase,3wir
esyst
em
whentheyar
earr
angedinahor i
zont
alplanewit
hspacingsuchthatD31=4m,D12=
D23=2m.Theconductorsaretr
ansposedandhav eadiameterof2.
5cm.
a.
2.22mH
b.
1.11mH
c.
3.33mH
d.
4.44mH
ANSWER:
b.1.
11mH
Q5.Asshowni nthefi
gthespacingofadoublecir
cuit3phaseov er
headline.
The
phasesequenceisABCandt heli
neiscomplet
elytransposed.Theconductorradi
us
i
s1.3cm.Findt hei
nductanceperphaseperki
lometre.
a.0.
57mH
b.5.
7X10^(
-7)H
c.5.
7x10^
(-7)mH
d.0.
57mH/perkm
a.0.
ANSWER: 57mH
Q6.Whyi
shi
ghv
olt
aget
ransmi
ssi
onl
inest
ransposed?
a.
Cor onal
ossescanbemi ni
mized.
b.Computat
ionofinductancebecomeseasi er
.
c.
Voltagedropsi
nt heli
nescanbemi nimized.
d.Phasevol
tagei
mbal ancescanbemi nimized.
ANSWER:
d.Phasev
olt
agei
mbal
ancescanbemi
nimi
sed.
Q7.Thet
hreephasel
ineconsi
stsofthreeconduct
orseachofdi
amet
er21mm.The
spaci
ngi
sshowni nf
ig.Fi
ndtheinduct
anceperphase/km.
a.
-
4
ANSWER:
b.12.
22*10 H/km
Q8.Wheni
sthet
ransposi
ti
onofconduct
orsi
nat
ransmi
ssi
onl
inedone?
a.
Whent heconductorsar
enotequallyspaced.
b.Whentheconductorsarespacedequil
ater
all
y.
c.
Whenat elephoneli
nerunsparal
lel
tothepowerli
ne.
d.Noneofthese.
ANSWER:
a.Whent
heconduct
orsar
enotequal
lyspaced.
Q9.Asserti
on(A):Tr
ansposi
ti
onofconduct
orsinatr
ansmissi
onlinei
s
necessary
.Reason(R):Cor
onalossesar
ereducedbytr
ansposi
ti
onof
conductor
s.
a.
BothAandRar etrueandRi
sthecorr
ectexpl
anat
ionofA
b.BothAandRaretrueandRi
snottheexpl
anati
onofA
c.
Ai str
uebutRisfalse
d.Aisfal
sebutRistrue.
ANSWER:
c.Ai
str
uebutRi
sfal
se
Q10.Asserti
on(A):t
heconceptofGMDi sappli
cablef
orthecal
culat
ionof
i
nductanceoftransmissi
onlines.
Reason(R):Theradi
usoft heconduct
oroftransmissi
onli
nes,i
nthe
expr
essionfori
nductanceisnottheselfGMDoft heconduct
or.
a.
BothAandRar etrueandRi
sthecorr
ectexpl
anat
ionofA
b.BothAandRaretrueandRi
snottheexpl
anati
onofA
c.
Ai str
uebutRisfalse
d.Aisfal
sebutRistrue.
ANSWER:
b.Bot
hAandRar
etr
ueandRi
snott
heexpl
anat
ionofA
Q11.I
ncaseofst
randedconduct
ors,
whati
sther
ati
ooft
heGMRt
otheact
ualr
adi
us?
a.
Equalto1
b.
Mor ethan1
c.
Equalto0.7788
d.Lesst
han0.7788
ANSWER:
d.Lesst
han0.
7788
Q12.Dsi
stheGMRofeachsubconduct
orofaf
oursubconductorbundl
edconductor
anddisthebundl
espaci
ng.Whati
stheGMRoftheequi
valentsi
ngleconduct
or?
3
a.1.
09√(Ds*d)
3 3
b.1.
09√(Ds *d)
c.1.
09(
√(Ds *d3)
3
)1/
4
3 1/
4
d.1.
09(
√(Ds*d) )
ANSWER:
d.1.
09(
√(Ds*d3)
)1/
4
Fer
rant
iEf
fect-MCQswi
thAnswer
s
Q1.Whendoest
heFer
rant
ief
fecthappenont
het
ransmi
ssi
onl
ine?
a.
Whent heli
neisshortandloaded.
b.Whentheli
neislongandloaded.
c.
Whent heli
neislongandunloaded.
d.Noneofthese.
ANSWER:
c.Whent
hel
i
nei
slongandunl
oaded.
Q2.Wheni
stheFer
rant
ief
fectont
hel
ongt
ransmi
ssi
onl
inesexper
ienced?
a.
Thelinei
sli
ghtl
yl oaded.
b.Thel
inei
sheavilyloaded.
c.
Thelinei
sful
lyloaded.
d.Thepowerf
actorisunity.
ANSWER:
a.Thel
inei
sli
ght
lyl
oaded.
Q3.Cor
rect
lymat
cht
hei
temsi
nLi
st1t
othei
temsi
nLi
st
2:Li
st1
A.SkinEff
ect
B.Proxi
mityEffect
C.Ferr
antief
fect
D.Sur
gei
mpedance
Li
st2
1.
Incr
easeinresistancebutdecreaseinsel
finduct
ance.
2.
Incr
easeinacr esistance.
3.
Owingtov ol
tagedr opacr ossl
i
neinduct
anceduet ofl
owofachar
gingcur
rent
.
4.
Squarerootofratioofl i
neimpedanceandshuntadmitt
ance.
Codes:
ABCDa.
2134
b.1243
c.3421
d.4312
ANSWER:
a.A2,
B1,
C3,
D4
UnderGr
oundCabl
es-MCQswi
thAnswer
s
Q1.Tr
ansmi
ssi
onofpowerbyaccabl
esi
simpossi
blebey
ond
a.35–45km
b.500km
c.300km
d.10–15km
ANSWER:
a.35–45km
Q2.Whatdoest
hebeddi
ngont
hecabl
econsi
stsof
?
a.
Jutestrands
b.Hessi
ant y
pe.
c.
Papertapecompoundedwi
thaf
ibr
ousmat
eri
al.
d.Anyofthese.
ANSWER:
d.Anyoft
hese.
Q3.Whyar
esheat
hsusedi
ncabl
es?
a.
Providepr operi
nsul
ati
on.
b.Pr
ovidemechani cal
str
ength.
c.
Preventingressofmoistur
e.
d.Noneoft hese.
ANSWER:
c.Pr
eventi
ngr
essofmoi
stur
e.
Q4.Whyar
econdui
tpi
pesempl
oyed?
a.
Toprotectunsheat
hedcabl
es.
b.
Armouredcables.
c.
PVCsheat hedcabl
es.
d.
All
ofthese.
ANSWER:
a.Topr
otectunsheat
hedcabl
es.
Q5.Thethi
cknessofi
nsul
ati
onl
ayerpr
ovi
dedont
heconduct
or,
incabl
es
dependon .
a.
Operati
ngv ol
tage
b.Cur
renttobecarri
ed.
c.
Powerf act
or.
d.Bot
h(a)and(b)
ANSWER:
a.Oper
ati
ngv
olt
age
Q6.Thesur
gei
mpedanceoft
hecabl
eis
(
A)14.
1ohms
(
B)42.
5ohms
(
C)87.
75ohms
(
D)141.
2ohms.
ANSWER:
D.141.
2ohms.
Q7.Thecapaci
tanceofcabl
eperkm i
s
(
A)0.
1mi
croF
(
B)0.
7mi
croF
(
C)1.
5mi
croF
(
D)10mi
croF.
ANSWER:A.0.
1mi
croF
UnderGr
oundCabl
es-
II-MCQswi
thAnswer
s
Q1.Whati
sthepur
poseofbeddi
ngont
heunder
groundcabl
es?
a.
Toavoidleakageofcur
rent.
b.
Toprotectthesheat
hagainstcor
rosion.
c.
Toprotectthesheat
hfr
om mechani cali
njur
yduet
oar
mour
ing.
d.
Bot
h( b)and(c)
ANSWER:
d.Bot
h(b)and(
c)
Q2.Armour
ingispr
ovidedabov
ethebeddi
ng.Thear
mour
ingconsi
stsofoneort
wo
l
ayersofwhichwi
reortape?
a.
Galvani
sedsteelwi
re.
b.Thi
nwiresofcopper.
c.
Wi r
esofalumini
um.
d.Wir
emadeofbot hcopperandcadmi
um.
ANSWER:
a.Gal
vani
sedst
eelwi
re.
Q3.Whyar
ethei
ntersheat
hsi
ncabl
esused?
a.
Providesproperstr
essdi st
ri
but
ion.
b.Mini
misesthestress.
c.
Providesprotect
ionagainstmoist
ure,
cur
rentandv
olt
agesur
ges.
d.Toimprovetheinsulat
ion.
ANSWER:
a.Pr
ovi
despr
operst
ressdi
str
ibut
ion.
Q4.Alayersi
mil
art
obeddingisprov
idedonthear
mour
ingt
opr
otectt
hewhol
ecabl
e
fr
om allat
mospher
iccondi
ti
ons.Whichl
ayeri
sthi
s?
a.
Insul
ati
on.
b.
Al ay
erofj
ute.
c.
Servi
ng.
d.
Sheath.
ANSWER:
c.Ser
ving.
I
nsul
ati
on&I
nsul
ati
ngmat
eri
als-MCQswi
thAnswer
s
Q1.Thet
hicknessofi
nsul
ati
onpr
ovi
dedont
heconduct
ori
nthecabl
edependson
which
amongt
hef
oll
owi
ngf
act
or?
a.
Operati
ngv ol
tage.
b.Cur
renttobecarri
ed.
c.
Powerf act
or.
d.Bot
h(a)and(b).
ANSWER:
a.Oper
ati
ngv
olt
age.
Q2.Theinsul
ati
onr
esi
stanceofacabl
eoflength10km is1M Ω.Foral
engt
hof100
km oft
hesamecable,
whatwillbet
heinsul
ati
onresi
stance?
a.
1M Ω
b.
10M Ω
c.
0.1M Ω
d.
0.01M Ω
ANSWER:
c.0.
1M Ω
Q3.Whati
sthemai
ndr
awbackofusi
ngpaperast
hei
nsul
ati
ngmat
eri
al?
a.
Ishy
groscopi
c
b.
Haspoordiel
ectr
icstr
engt
h.
c.
Hasav er
ylowinsul
ati
onresi
sti
vi
ty.
d.
Hashighcapaci
tance.
ANSWER:
a.I
shy
groscopi
c
Q4.Whati
sthel
imi
toft
heconduct
orcr
osssect
ionwhenpaperi
nsul
ati
oni
sused?
a.50mm2
b.250mm2
c.600mm2
d.1200mm2
c.600mm2
ANSWER:
Q5.Whati
sthedi
elect
ri
cst
rengt
hofi
mpr
egnat
edpaper
?
a.
30kV/mm
b.
20kV/mm
c.
15kV/mm
d.
5kV/mm
ANSWER:
a.30kV/
mm
Q6.Whati
sempi
ret
ape?
a.
Impregnatedpaper
b.
Vulcanisedrubber
c.
Enamel insul
ati
on
d.
Varnishedcambr i
c
ANSWER:
d.Var
nishedcambr
ic
Q7.Whati
st hepercent
ageofaddedmat
eri
alsl
ikesul
phur
,zi
ncl
eadet
cin
vul
cani
sedrubber?
a.5–10%
b.3–5%
c.4–8%
d.10–12%
ANSWER:
b.3–5%
Cabl
ety
pes-MCQswi
thAnswer
s
Q1.Howmanycor
esar
eusedi
nacabl
efort
het
ransmi
ssi
onofv
olt
agesupt
o66kV?
a.
Singl
ecore.
b.Twocore.
c.
Threecore.
d.Al
loft
heabove.
ANSWER:
c.Thr
eecor
e.
Q2.Whyi
sthesi
ngl
ecor
ecabl
esnotpr
ovi
dedwi
thar
mour
ing?
a.
Avoi
dsexcessiv
el ossinthearmour.
b.
Makethecablemor efl
exible.
c.
Makethecablenonhy groscopic.
d.
Noneoftheabov e.
ANSWER:
a.Av
oidsexcessi
vel
ossi
nthear
mour
.
Q3.Whi
chamongt
hef
oll
owi
ngcabl
esar
egener
all
ysui
tedf
ort
hev
olt
agesupt
o11kV?
a.
Belt
edcables
b.
Screenedcables
c.
Pressurecables
d.
Noneoft hese.
ANSWER:
a.Bel
tedcabl
es
Q4.Whi
chmat
eri
ali
ssui
tabl
efort
hemanuf
act
ureofar
mouri
nasi
ngl
ecor
ecabl
e?
a.
Magneticmater
ial
.
b.Nonmagneti
candnonconducti
ngmateri
al.
c.
Nonmagnet i
candconduct
ingmater
ial
.
d.Magnet
icandnonconduct
ingmater
ial
.
ANSWER:
c.Nonmagnet
icandconduct
ingmat
eri
al.
Q5.Whyt
hebel
tedt
ypecabl
econst
ruct
ionsar
enotsui
tabl
eforv
olt
agesexceedi
ng22
kV?
a.Developmentofbot hradial
andtangential
stress.
b.Format i
onofv acuousspacesandv oi
dsonl oadingandunl
oadi
ngowi
ngt
onon
homogenei tyofdiel
ectr
icinbelt
edconstructi
on.
c.Localheatingcausedbypowerl ossatthecentrefil
l
ing.
d.Alloftheabove.
ANSWER:
d.Al
loft
heabov
e.
Q6.Thecabl
ebestsui
tedf
ort
het
ransmi
ssi
onofv
olt
agesf
rom 33kVt
o
66kVis .
a.
Belt
edcables
b.
Screenedcables
c.
Pressurecables
d.
Noneoft hese.
ANSWER:
b.Scr
eenedcabl
es
Q7.Whati
s/ar
etheadv
ant
agesofusi
ngH-
typecabl
es?
a.
Themet al
l
icscreensassistincomplet
ei mpregnat
ionoft
hecablewi
ththecompound.
b.Themet al
li
cscreensincreasetheheatdissi
pati
ngpowerofthecabl
e.
c.
Thel eadsheathsinHt ypearethi
ckerthenS.Ltypecabl
es.
d.All
ofthese.
ANSWER:
d.Al
loft
hese.
Q8.Whati
stheadv
ant
age(
s)ofscr
eenedt
ypeov
ert
hebel
tedcabl
es?
a.
Reducedpossi
bil
it
yofcoret
ocor efaul
ts.
b.I
ncr
easedcurr
entcar
ryi
ngcapacit
y.
c.
Nopossibi
li
tyoff
ormati
onofvoidswi t
hint
hedi
elect
ri
c.
d.
All
oft
heabov
e.
ANSWER:
d.Al
loft
heabov
e.
Q9.Whati
sthegaspr
essur
eofSF6f
oracompr
essedgasi
nsul
atedcabl
e?
a.10–20mm Hg
b.80–100mm Hg
c.3–5kg/cm2
d.40–50kg/cm2
c.3–5kg/cm2
ANSWER:
Q10.Whyar
ethet
ernar
yleadcabl
esusedneart
her
ail
wayt
racks?
a.
Becausetheyhavehi ghtensi
lestrengt
h.
b.Havealowcoeffi
cientofthermalexpansi
on.
c.
Hav el
owspecifi
cgr avi
ty.
d.Canwit
hstandshocksandv i
brat
ions.
ANSWER:
c.Hav
elowspeci
fi
cgr
avi
ty.
Q11.Whysol
idt
ypeofconduct
orsi
snotpr
efer
redf
ort
hev
olt
agesexceedi
ng66kV?
a.
Adangerofbr eakdownofi nsulat
ion.
b.Ski
neffectdominatestheconduct or
.
c.
Thereiscoronalossbet weenconduct orandsheat
hmat
eri
al.
d.I
nsulat
ionmeltsduet ooverheati
ng.
ANSWER:
a.Adangerofbr
eakdownofi
nsul
ati
on.
I
nsulat
ionResi
stancei
nUnder
groundCabl
es-MCQs
wit
hAnswers
Q1.Asi
ngl
ecorecabl
ehasaconductordi
ameterof1cm andtheinsul
ati
onthi
ckness
14
of0.
4cm.I
fthespeci
fi
cresi
stanceofi
nsul
ati
onis5.
5*10 Ω- cm,whatwil
lbethe
i
nsul
ati
onr
esist
ancef
oralengthof3km?
234*109Ω
a.0.
257*109Ω
b.0.
352*109Ω
c.0.
211*109Ω
d.0.
ANSWER: 257*109Ω
b.0.
Q2.Asingl
ecorecable5km l
onghasaninsulat
ionresi
stanceof0.35M Ω.Thecor
e
di
ameteris20mm andt hedi
ameteroft
hecableovertheinsul
ati
onis50mm.What
wil
lbetheresi
sti
vi
tyoft
heinsul
ati
ngmateri
al?
a.13*109Ωm
9
b.12*10 Ωm
5*109Ωm
c.13.
9
d.12.
85*10 Ωm
b.12*109Ωm
ANSWER:
Q3.Onwhi
chf
act
ordoest
hecapaci
tanceoft
hecabl
edependupon?
a.
Lengthofcabl
e.
b.
Relati
vepermitt
ivi
tyofdiel
ect
ri
cusedincabl
e.
c.
Ratioofsheat
hdi ameterandcoredi
ameter
.
d.
Alloftheabove.
ANSWER:
d.Al
loft
heabov
e.
Q4.Thechar
gingcur
rentdr
awnbyt
hecabl
e .
a.
Lagsbehindt
hev ol
tageby90°.
b.
Leadsthevol
tageby90°.
c.
Areinphasewit
heachot her
.
d.
Leadsthevol
tageby60°.
ANSWER:
Leadst
hev
olt
ageby90°
.
Q5.Asingl
ecorecablehasaconductordi
ameterof1cm andthei
nter
nalsheat
h
di
ameterof1.
8cm.I fimpr
egnatedpaperofr
elat
iveper
mitt
ivi
ty4i
susedast he
i
nsul
ati
on,cal
culat
ethecapaci
tancefor1km l
engthofcabl
e?
a.0.
378μF
b.0.
264μF
c.0.
549μF
d.0.
78μF
ANSWER:
a.0.
378µF
Q6.Whatisthetotalchargi
ngcur r
entperphasefora33kV,50Hz,3phase
under
groundcableof4km l engthusing3singl
ecorecabl
es?Eachconduct
orhasa
di
ameterof2.5cm andt heradialt
hicknessofi
nsulat
ioni
s0.5cm
a.15.
28A
b.11.
87A
c.13.85A
d.8.25A
ANSWER:
b.11.
87A
Di
elect
ri
cSt
ressi
naSi
ngl
eCor
eCabl
e-MCQs
wi
thAnswer
s
Q1.Whatist
hemaximum str
essi
ntheinsul
ati
onfora33kVsi
ngl
ecor
ecabl
ewi
tha
di
ameterof1cm andasheat
hofi
nsidediameter4cm?
a.
50.
61kV/cm rms
b.
45.
231kV/cm rms
c.
47.
61kV/cm rms
d.
49.
231kV/cm r
ms
ANSWER:
c.47.
61kV/cm r
ms
Q2.Whatwi
llbet
heinsul
ati
onthi
cknessf
oraconduct
orofdi
amet
er2cm, with
maxi
mum andminimum str
ess40kV/cm rmsand10kV/cm rmsrespect
ivel
y?
a.
5cm
b.
3cm
c.
2cm
d.
4cm
ANSWER:
b.3cm
Q3.Whatwil
lbet
hemosteconomicalval
ueofdi
ameterofasi
ngl
ecorecabl
etobe
usedon50kV,si
ngl
ephasesyst
em, whenthemaxi
mum permi
ssi
blest
ressi
snot
exceedi
ng50kV/cm?
a.2.
52cm
b.2.
828cm
c.3.
52cm
d.3.
82cm
ANSWER:
b.2.
828cm
Q4.Togetamini
mum val
ueofst
ress(
gmax)whatshoul
dbet
her
ati
oofcor
e
di
ametert
osheathdi
ameter
?
a.1/2.
718
b.2.
178
c.1/3.
78
d.3.
78
ANSWER:
a.1/2.
718
GradingofCabl
es&Capaci
tanceofThr
eecor
e
cables-MCQswi t
hAnswer
s
Q1.Whatdoescapaci
tancegr
adi
ngofcabl
esmean?
a.
Useofdi elect
ricsindi
ffer
entconcentrati
ons.
b.I
ntroductionofcapacitanceatv ar
iouslengthsofcabl
etocount
ert
heef
fectof
i
nduct ance.
c.
Useofdi elect
ricsofdif
ferentpermit
ti
viti
es.
d.Gradingaccor dingtocapacit
anceperkm l engt
hofthecabl
e.
ANSWER:
c.Useofdi
elect
ri
csofdi
ff
erentper
mit
ti
vi
ti
es.
Q2.Ina3corecable,t
hecapacit
ancebet
weent
woconduct
orsi
s3μF.Whatwi
ll
bethecapaci
tanceperphase?
a.
1.5μF
b.
3μF
c.
6μF
d.
12μF
ANSWER: c.6μF
Q3.Fort
hef i
gshown,
whatwi
llbet
hecapaci
tancebet
weenAandB
a.
CC+(
CS/2)
b.Cs+(Cc/2)
c.
( CS+3Cc)/2
d.3CC+2CS
ANSWER:
c.(
CS+3Cc)/2
Q4.Whati
sthesour
ceofheatgener
ati
oni
ncabl
es?
a.
Copperlossinconductor
b.
Dielect
ri
clossesincablei
nsul
ati
on
c.
Lossesinmet al
li
csheathi
ngsandarmour
ing.
d.
Allofthese.
ANSWER:
d.Al
loft
hese.
Q5.Thecapacit
ancesofa3phasebel t
edcablear
e12. 6μFbetweenthethreecores
bunchedtoget
herandtheleadsheathand7.
4μFbet weenonecoreandtheothertwo
connect
edtosheath.Whatwillbet
hechargi
ngcurrentdrawnbythecabl
ewhen
connect
edtoa66kVsuppl y?
a.100A
b.99.3648A
c.105.236A
d.107.74A
ANSWER:
d.107.
74A
Q6.Whati
sthesaf
ewor
kingt
emper
atur
eforaconduct
ori
ncaseofar
mour
edcabl
es?
a.
50°C
b.
75°C
c.
65°C
d.
40°C
ANSWER:
c.65°C
Q7.Whi
cht
est
sar
econduct
edt
olocat
ethef
aul
tlocat
ioni
nthecabl
es?
a.
Mur rayloopt est
.
b.Var
leyloopt est.
c.
Both( a)and( b).
d.Noneoft hese.
ANSWER:
c.Bot
h(a)and(
b).
Q8.I
nat estbyMurrayloopforgroundfaul
ton500m ofcabl ehavi
ngar esi
stanceof
1.
6Ω/km, thefaul
tycablei
sloopedwiththesoundcableofsomel engt
handar eaof
cr
osssection.I
ftherati
ooftheothertwoarmsoft het
esti
ngnet workatbal
anceis
3:
1,whatisthedist
anceoffaultf
rom thetest
ingendofcables?
a.
100m
b.
200m
c.
250m
d.
300m
ANSWER:
c.250m
Li
neSuppor
ts-MCQswi
thanswer
s
Q1.Forhi
ghv
olt
aget
ransmi
ssi
onl
ines,
whyar
econduct
orssuspendedf
rom t
ower
s?
a.
Incr
easetheclearancefrom ground.
b.
Reduceclear
ancef rom ground.
c.
Takecareofincreaseinlength.
d.
Reducetheenv i
ronmental ef
fects.
ANSWER:
a.I
ncr
easet
hecl
ear
ancef
rom gr
ound.
Q2.I
nIndi
a,whi
cht
ypesofpol
esar
ecommonl
yusedf
ordi
str
ibut
ion?
a.
Woodenpol es.
b.
RCCpol es.
c.
Steel
poles.
d.
Both(b)and( c)
ANSWER:
d.Bot
h(b)and(
c)
Q3.Whi
chamongt
hesear
ethepr
oper
ti
esf
ort
hel
inesuppor
ts?
a.
Highermechanicalst
rengt
h.
b.Li
ghti
nwei ght
.
c.
Easyaccessibi
li
tyofconduct
orsf
ormai
ntenance.
d.Al
lofthese.
ANSWER:
d.Al
loft
hese.
Q4.Whati
sthemaxi
mum per
missi
blel
imi
tofv
olt
agef
ort
hel
inesuppor
ts?
a.
30kV
b.
20kV
c.
11kV
d.
44kV
ANSWER:
b.20kV
Q5.Topr
eventr
ott
ingoi
lthewoodenpol
eswhi
choi
lisi
mpr
egnat
edt
oit
?
a.
Keroseneoil
.
b.Mi
neraloi
l.
c.
Creosoteoi
l.
d.Al
ltheabove.
ANSWER:
c.Cr
eosot
eoi
l.
Q6.St
eelpol
esar
epai
ntedsoast
opr
eventi
tfr
om
a.
Corrosion.
b.
Borer.
c.
Termites.
d.
All
oft hese.
ANSWER:
a.Cor
rosi
on.
Q7.Whi
chamongt
hesei
snotat
ypeofst
eelpol
es?
a.
Rai
lpol
es.
b.
Tubul
arpoles.
c.
Rol
ledst
eel j
oint
s.
d.
Noneofthese.
ANSWER:
d.Noneoft
hese.
Q8.Whati
stheusualspanoft
heRCCpol
es?
a.250–400m.
b.80–150m.
c.50–105m.
d.10–75m.
ANSWER:b.80–150m.
Q9.Whati
sthemai
npur
posef
orguywi
re?
a.
Suppor t
sthepole.
b.
Protectsagai
nstthesur
ges.
c.
Providesemergencyear
throut
e.
d.
Allofthese.
ANSWER:
a.Suppor
tst
hepol
e.
Q1.Whati
scor
ona?
a.
Parti
albreakdownofair
.
b.Complet
ebr eakdownofair
.
c.
Sparki
ngbet weentheli
nes.
d.Noneofthese.
ANSWER:
b.Compl
etebr
eakdownofai
r.
Q2.I
ncaseofdcv
olt
age,
whi
chcol
ourbeadsar
efor
medneart
henegat
iveconduct
or?
a.
Reddish.
b.
Blui
sh.
c.
Greenish.
d.
Viol
et.
ANSWER:
a.Reddi
sh.
Q3.I
ncaseofdcv ol
tage,
smoot
her uni
for
m gl
owneart
he
posi
ti
veconduct
or.
a.
Yell
ow.
b.Bl
uishwhi
te.
c.
Reddishwhit
e.
d.Gr
eenishy
ell
ow.
ANSWER:
b.Bl
uishwhi
te.
Q4.Whi
choft
hef
oll
owi
ngst
atement
sar
etr
uer
elat
edt
ocor
ona?
1.
Itcausesradi
ointerf
erence.
2.
Itatt
enuatesl
ightni
ngsurges.
3.
Itcausespowerloss.
4.
Itamplif
iesswit
chingsurges.
Thecodesar
e:
a.1,
2,
4
b.1,
4
c.1,
2,
3
d.2,
3
ANSWER:
c.1,
2,
3
Q5.Whi
chgasi
sfor
medneart
otheconduct
orsbypr
oduci
ngahi
ssi
ngnoi
se?
a.
Oxy gen.
b.Ozone.
c.
Hy drogen.
d.Nit
rogen.
ANSWER:
b.Ozone.
Q6.Cor
onai
sobser
vedon
a.
ACt r
ansmissionsonly.
b.DCtransmissi
onsonly.
c.
ACandDCt r
ansmissi
ons.
d.Noneofthese.
ANSWER:
c.ACandDCt
ransmi
ssi
ons.
Fact
orsaf
fect
ingt
hecor
ona&cor
onal
oss-MCQs
wit
hAnswers
Q1.Hi
ghert
hef
requency
, .
a.
Lowerthecoronaloss.
b.
Higheri
sthecoronaloss.
c.
Doesnoteffect
.
d.
Dependsont hephysical
condi
ti
ons.
ANSWER:
b.Hi
gheri
sthecor
onal
oss.
Q2.Whi
chharmoni
csar
egener
ateddur
ingt
hecor
ona,
whi
chl
eadst
othei
ncr
easei
n
cor
onal
osses?
a.
Thir
dharmonics.
b.
Fif
thharmoni
cs.
c.
Sevent
hharmonics.
d.
Noneofthese.
ANSWER:
a.Thi
rdhar
moni
cs.
Q3.Whati
stheuseofbundl
edconduct
ors?
a.
Reducessur faceelectr
icstressofconduct
or.
b.I
ncreasesthelinereactance.
c.
Decr easesthelinecapacit
ance.
d.Noneoft hese.
ANSWER:
a.Reducessur
faceel
ect
ri
cst
ressof
conduct
or.Q4.Onwhi
chf
act
ori
sthecor
onal
oss
dependenton?
a.
Mat er
ialoftheconductor.
b.Di
amet eroftheconductor
.
c.
Heightoft heconduct
or.
d.Noneoft hese.
ANSWER:
b.Di
amet
eroft
heconduct
or.
Q5.I
nwhi
chcl
imat
edoest
hechancesofoccur
renceofcor
onai
smaxi
mum
a.
Dry
b.
Hotsummer
.
c.
Winter.
d.
Humi d.
ANSWER:
d.Humi
d.
Q6.Cor
onal
osscanber
educedbyusi
ng
1.
Sol
idconductor
.
2.
Holl
owconductor.
3.
Bundleconduct
or.
a.
1only
b.
1and2only.
c.
1,2and3onl
y.
d.
2and3only.
ANSWER:
d.2and3onl
y.
Q7.Whati
stheef
fectoncor
ona,
ift
hespaci
ngbet
weent
heconduct
orsi
sincr
eased?
a.
Coronaincreases.
b.Coronai
sabsent .
c.
Coronadecr eases.
d.Noneofthese.
ANSWER:
b.Cor
onai
sabsent
.
Q8.Whyar
ethehol
lowconduct
orsused?
a.
Reducet
hewei
ghtofcopper
.
b.I
mprovest
abil
it
y.
c.
Reducecorona
d.I
ncr
easepowertransmi
ssi
oncapaci
ty.
ANSWER:
c.Reducecor
ona
Q9.Whichofthesegi
venst
atement
siswr
ongi
nconsi
der
ati
onwi
thbundl
ed
conduct
ors?
a.
Control
ofvolt
agegradient
.
b.
Reducti
onincoronaloss.
c.
Reducti
onintheradi
ointer
ference.
d.I
ncr
easeinint
erf
erencewithcommunicat
ionl
i
nes.
ANSWER:
d.I
ncr
easei
nint
erf
erencewi
thcommuni
cat
ion
l
ines.Q10.Whyar
ebundl
edconduct
orsempl
oyed?
a.
Appearanceofthetransmissi
onli
neisimproved.
b.Mechani
calst
abil
ityoftheli
neisi
mproved.
c.
Improvescurr
entcarryi
ngcapacit
y.
d.I
mprovesthecoronaperformanceofthel
ine.
ANSWER:
d.I
mpr
ovest
hecor
onaper
for
manceoft
hel
ine.
Q11.Theef
fectofdi
rtont
hesurfaceoft
heconductori
sto i
rr
egul
ari
tyand
t
hereby thebr
eakdownv ol
tage.
a.
Decr eases,
reduces.
b.I
ncreases,i
ncreases.
c.
Increases,r
educes.
d.Decreases,i
ncreases.
ANSWER:
c.I
ncr
eases,
reduces.
Q13.Fi
ndthespacingbet
weentheconduct
orsa132kV3phaseli
newith1.
956cm
di
ameterconduct
orsisbui
ltsot
hatcor
onatakespl
ace,
ift
hel
inevol
tageexceeds
210kV(rms).Wit
hgo=30kV/ cm.
a.1.
213m
b.2.
315m.
c.3.
451m.
d.4.
256m.
ANSWER:
c.3.
451m.
Uni
t5
Capaci
tanceofov
erheadTr
ansmi
ssi
onl
i
neMCQs
1.Thepr
esenceofear
thi
ncaseofov
erheadl
i
nes
a)I
ncreasesthecapacit
ance
b)I
ncreasestheinduct
ance
c)Decreasesthecapaci
tanceandi
ncreasest
hei
nduct
ance
d)Doesnoteffectanyoftheli
neconstant
s
Ans:a
2.I
ftheef
fectofear
thi
stakeni
ntoaccount
,thent
hecapaci
tanceofl
i
net
ogr
ound
a)Decreases
b)I
ncreases
c)Remainsunaltered
d)Becomesi nf
init
e
Ans:
b
3.I
nat
ransmi
ssi
onl
i
net
hedi
str
ibut
edconst
ant
sar
e
a)Resi
stanceandshuntconductanceonly
b)Resi
stanceandinduct
anceonly
c)Resi
stance,
induct
anceandcapacitanceonl
y
d)Resi
stance,
induct
ance,capaci
tanceandshuntconduct
ance.
Ans:
d
4.Tr
ansposi
ti
onoft
ransmi
ssi
onl
i
nei
sdonet
oreducet
he
a)Li
nelosses
b)Capacit
iveeff
ect
c)Di
sturbancetonearbycommunicat
ionci
rcui
ts
d)Ef
fectofsurgevolt
agesinducedonthel
i
ne
Ans:
C
5.Thepr
esenceofear
thi
ncaseofov
erheadl
i
nes
a)I
ncreasesthecapacit
ance
b)I
ncreasestheinduct
ance
c)Decreasesthecapaci
tanceandi
ncreasest
hei
nduct
ance
d)Doesnoteffectanyoftheli
neconstant
s
Ans:
a
6._
___
___i
snegl
ect
edwhi
l
ecar
ryi
ngoutshor
ttr
ansmi
ssi
onl
i
neanal
ysi
s.
a)Shuntadmitt
ance
b)Powerlosses
c)Seriesi
mpedance
d)Noneoft hementi
oned
Ansa:Inshorttr
ansmi
ssi
onl
ineasl
engt
handv
olt
agei
ssmal
lthi
sshunt
admi
tt
anceef
fecti
snegl
ect
ed.
7.Wetransposehi ghvol
tagesespecial
l
ywhi
let
ransmi
tt
ingsot
hatt
he_
___
___
___
a)phasev oltageimbalancescanbemi
nimi
sed
b)coronal ossesarereduced
c)voltagedropismi ni
mi sed
d)all
oft hement i
oned
Ans:aTransposi
ti
onr
educest
hephasev
olt
agei
mbal
ancesbycancel
l
ingt
hei
r
ef
fect
s.
8.Whilemodel l
i
ngashortt
ransmi
ssi
onli
neoftheover
headl
ines,l
i
neresi
stance
andinduct ancesareonl
yconsi
der
edbecauset
heli
necapaci
tanceis_
____
______
a)zero
b)fini
tebutsmal l
c)finitebutlarge
d)inf i
nit
e
Ansb:
capaci
tancef
orsuchadi
stancei
ssmal
landbegl
i
gibl
e.
9.Thechar
gingcur
rentdr
awnbyt
hecabl
eis
a.Lagsvolageby90o
t
b.Leadv ol
tageby90o
c.Leadvolageby45o
t
d.Noneoft heabov e
Ans: C Thechargingcur
rentdr
awnbyt
hecabl
eiscapaci
ti
vei
nnat
ure,
ther
efor
e,i
t
l
eadst hevol
tageby 90
10.Thepowerl
ossi
n at
ransmi
ssi
onl
i
nei
smai
nlyduet
o--
--
--
--
--
--
-
a.Resi
stance
Binduct
ance
Ccapacitance
Ans: a
11.I
fthel
engt
hofat
ransmi
ssi
onl
i
nei
ncr
eases,
itsi
nduct
ancei
s--
--
--
--
--
--
-
a.decreases
bincreases
citdependsupont
hecondi
ti
on
d.cannotsay
Ans:
b
12.
Thedcr
esi
stanceofal
i
neconduct
ori
s--
--
--
--
--
--t
hani
t’
sa.
c.r
esi
stance.
a.more
b.less
Ans:B Becauseofski
nef
fectacr
esi
stancei
slesst
handcr
esi
stance
13.Ifcapaci
tancebet
weentwoconduct
orsofa3phasel
i
nei
s4mi
crof
arad,
then
capacit
anceofeachconduct
ort
oneutrali
s--
--
--
a.4micr ofarad
b.16mi crofar ad
c.8micr ofarad
d.Datainsufficient
Ans:cCapaci tancebetconduct
orandneut
ral
isdoubl
ethant
hecapaci
tance
bet
weent hetwoconduct ors
14.I
fthel
engt
hoft
hel
i
nei
sdecr
eased,
itscapaci
tancei
s--
--
--
--
--
-
a.i
ncreased
b.decreased
Ans:b
15.Tr
ansposi
ti
onofa3phaset
ransmi
ssi
onl
i
nehel
psi
n--
--
--
--
--
--
a.r educi
ngv olt
agedrop
b.equali
singinduct
anceandcapacit
anceoft
hethr
eephases
c.increasingtheeff
ici
encyoft
ransmissi
onl
ine
Ans: B
16.Aneut
ral
planei
sonewher
e--
--
-iszer
o
a.El
ect
ri
cfluxdensit
y
b.El
ect
ri
cfil
edstrength
c.El
ect
ri
cintensi
ty
Ans:
C
17.I
fthesuppl
yfr
equencyi
ncr
eases,
thenski
nef
fecti
s--
--
--
--
--
-
a.i
ncreases
b.decreases
Ans: a
18.I
fthespaci
ngbet
weent
heconduct
orsi
sincr
eased,
thei
nduct
anceoft
hel
i
ne-
--
--
-
--
--
--
a.i
ncreases
b.decreases
Ans.A
19.Theski
nef
fecti
s--
--
--
--
--
--
--
-forst
randedconduct
ort
hant
hesol
i
dconduct
or
a.l
ess
b.more
Ans:a
20.I
ftheconduct
ordi
amet
erdecr
eases,
i
nduct
anceoft
hel
i
nei
s--
--
--
--
a.decreases
b.i
ncreases
Ans:b
21. Whi
choft hesegivenstatementsiswrongi
nconsi
der
ati
onwi
thbundl
ed
conductors?
a.
Control
ofv ol
tagegradient
b.
Reducti
onincor onaloss
c.
Reducti
onint heradi
ointer
ference
d.
Incr
easeininterf
erencewithcommunicati
onl
ines
Ans:d
22.Onwhatf act
ordoestheskinef
fectdepend?
a.
Crosssect i
onoftheconduct
ors
b.
Supplyfrequency
c.
Permeabi l
i
tyoftheconduct
or
d.
Allofthese
Ans:d
23.A3phaseov er
headt r
ansmissi
onli
nehasitsconductor
sarr
angedatt
he
corner
sofanequil
atral
tri
angl
eof2m side.Thecapaci
tanceofeachl
i
neconduct
or
perkm is-
--
-.Thediameterofeachconduct
oris1.
25cm
a.0.
0096mi
crof
arad/
km
b.0.
096mi
crof
arad/
km
0096x10-9f
c.0. /km
Ans:a
24.A250V,
50Hz1phase60km t
ransmi
ssi
onl
i
neconsi
sti
ngof2par
all
elwi
res
each5mm indiameterand1.5m apar
t.Thehei
ghtofconduct
orsabov
egr
oundi
s7
m.Deter
minetotal
capacit
anceofli
ne
718x10-3mi
a.8, crofar
ad/
m
-
3
b.8.
718x10 f ar
ad/m
-9
c.8.
718x10 f arad/
m
Ans: a
25.Fi
ndoutthecapaci
tanceofasi
nglephasel
i
ne30km longconsi
sti
ngoft
wo
paral
l
elwi
reseachof15mm di amet
erand1.5m apar
t.
a.0.
1575Farad
b.0.
1575microfar
ad
-
9
c.5.
2499x10 F
Ans:b
26.Asinglephaset
ransmi
ssi
onlinehastwoparal
l
elconduct
ors3.
5m apartfr
om
eachother
.Theradi
usofeachconductorus1.
5cm .Cal
culat
ecapaci
tanceofl
ine
perki
l
omet re,
a.1.02x10-8F/
m
-
8
b.1.02x10 F/Km
-
8
c.1.
02x10 F/ Km
ans: b
27.Whent woconductor
seachofradi
usrar
eatadi
stanceD,
thecapaci
tance
betweent hetwoisproport
ional
to
a.loge
(D/r)
b.loge
(r/D)
c.1/loge (
D/r
)
d.1/l
oge (r
/D).
Ans:
c
28.Incasetheheightoft
ransmi ssi
ontowerisincr
eased
a.thel
inecapaci
tanceandi nductancewi
llnotchange
b.theli
necapaci
tancewilldecreasebutl
ineinduct
ancewil
ldecr
ease
c.t
helinecapaci
tancewil
l decreaseandli
neinductancewi
l
lincr
ease
d.theli
necapaci
tancewilldecreasebutl
ineinduct
ancewil
lremainunal
ter
ed.
Ans:
d
29.Ift
heheightoftr
ansmissi
ontower
sisi
ncr
eased,
whi
choft
hef
oll
owi
ng
parameter
sisli
kelytochange?
a.Resi
stance
b.I
nductance
c.Capacit
ance
d.Noneoftheabov
e.
Ans:
C
30.Whichofthefoll
owingisreducedduet
otheuseofbundl
edconduct
ors?
a.Capacit
anceofthecircui
t
b.i
nductanceofthecir
cuit
c.Powerlossduetocorona
d.All
oftheabove.
Ans:
c
31.Asingl
ephaselinehavi
ng2singl
estrandedconduct
orandr
adi
us0.328cm.The
conductor
sarespaced4m apartabovetheground.Cal
cul
atet
hecapaci
tancet
o
neutr
alperkm.(consi
deri
ngear
th’
seffect)
a.0.
00784micr
of arad/
km
b.0.
00787micr
of arad/
km
c.0.
00784f
arad/km
d.Noneoft
heabov e.
Ansb
32.Asinglephaseli
nehaving2singl
estr
andedconduct
orandradi
us0.328cm.The
conductorsarespaced4m apartabovethegr
ound.Calcul
atet
hecapacit
ancet
o
neutr
al perkm.(negl
ect
ingeart
h’sef
fect
)
a.0.
00784micr
of arad/
km
b.0.
00787micr
of arad/
km
c.0.
00784f
arad/km
d.Noneoft
heabov e.
Ansa
33.A250V,50Hz,1phase60km l ongtr
ansmissi
onl
i
neconsisti
ngof2paral
lel
wireseach5mm i
ndiameterand1.5m apart
.Thehei
ghtofconduct
orsabove
groundis7m,Det
erminet
otalcapacit
anceofl
ine.
71x10-9f
a.8. arad/km
-
3
b.8.71x10 f arad/m
-3
c.8.
71x10 mi crof ar
ad/
m
d.Noneoftheabov e.
Ansc
34.Athr
eephase, 110kV,
50Hzoverheadli
neconductor
sareplacedinhori
zontal
pl
ane,
theconductordiameteri
s1.
5cm.I fthel
inel
engthis100km, assuming
compl
etetr
anspositi
onoftheli
ne,
calcul
atecapaci
tanceperphase(Linet
oneut r
al)
907x10-9f
a.0. arad
-
6
b.0.907x10 f arad
c.0.
907mi crof arad
d.Noneoft heabov e.
Ansc
35.At
hreephase,110kV,
50Hzoverheadlineconductor
sareplacedinhor
izont
al
pl
ane,
theconductordi
ameteri
s1.5cm.I ftheli
nelengt
his100km, assuming
compl
etetr
ansposit
ionoft
heli
ne,calcul
atechargi
ngcurrentperphase
a.18.098Amp
b.0.189Amp
c.180.98Amp
d.datainsuf
fi
cient
Ans: a
36Asinglephasel
inet
ransmi
t1000kW at10kVatap.f.of0.
85laggi
ng.I
thastot
al
l
oopresi
stanceof2ohm andi
nduct
iver
eactanceof3ohm ,Vol
tageregul
ati
onof
thel
i
neis
a.2.
85
b.2.90
c.3.
85
d.Datainsuf
fi
cient
Ans: c
Q.
37Capaci
tancebet
weenthetwoconductor
sofasinglephaset
wowi r
eli
nei
s0.
5
μF/km.Whati
stheval
ueofcapaci
tanceofeachconductort
oneut
ral
?
a.0.
5μF/km.
b.1μF/km.
c.0.
25μF/km.
d.2.
0μF/km.
Ans: B
Q38. Whathappensincaseofcapaci
tanceofl
i
net
ogr
ound,
ift
heef
fectofear
thi
s
takeni
ntoaccount?
a.Capaci
tanceofl
i
net
ogr
ounddecreases.
b.Capaci
tanceofl
i
net
ogr
oundi
ncreases.
c.Thecapaci
tanceremai
nsunal
ter
ed.
d.Thecapaci
tancebecomesi
nfi
nit
e.
Ans:
bCapaci
tanceofl
i
net
ogr
oundi
ncr
eases.
39.Whati
sthev
alueofcapaci
tancet
oneut
ral
fort
het
wowi
rel
i
ne?
a.Twicetheli
netoli
necapaci t
ance.
b.Equaltoli
netoli
necapacitance.
c.Thri
cethelinet
olinecapacit
ance.
d.Halfofli
netoli
necapacit
ance.
Ans:
a:Twi
cet
hel
i
net
oli
necapaci
tance
40.Atwoconductorsi
nglephaseli
neoperatesat50Hz.Diameterofeachconduct
or
i
s20mm andt hespaci
ngbet weentheconductor
sis3m.Thehei ghtofthe
conduct
orsabovethegroundis6m.Whatist hecapaci
tanceoftheli
netoneutr
al?
a.9.
7pF/m.
b.10.
8pF/m.
c.3.
57pF/m.
d.2.
415pF/m.
Ans:
a
Uni
t6
Quest
ionBank
Per
for
manceofTr
ansmi
ssi
onLi
ne
1.Whati
sthepowerf
act
orangl
eoft
hel
oadf
ormaxi
mum v
olt
ager
egul
ati
on?
a.tan-1 (X/
R)
-1
b.cos (X/R)
-1
c.tan (R/
X)
d.cos-1 (R/X)
Ans:a
2. Asingl
ephaset
ransmi
ssi
onli
neofi
mpedancej
0.8ohm suppl
i
esar
esi
sti
ve
loadof500Aat300V.Thesendi
ngendpowerf
actori
s
a.Uni
ty
b.0.8l
aggi
ng
c.0.8l
eadi
ng
d.0.6l
aggi
ng
Ans:
a
3. Whenthepowerist
obetransmi
tt
edoveradi
stanceof500k
m,t
het
ransmi
ssi
on
volt
ageshoul
dbeinther
ange
a.33kV-66k V
b.66kV-100k V
c.110kV-150k V
d.150kV-220kV.
Ansd
4.Lengt
hoflongt
ransmi
ssi
onl
i
nei
smor
ethan_
___
___
___
_
a)80Km
b)50Km
c)120Km
d)200Km
Ans:200Km
5. -
--
--oft
ransmi
ssi
onl
i
nesi
sthemosti
mpor
tantcauseofpowerl
ossi
nthe
li
ne.
a. Resi
stance
b.I
nduct
ance
c.Capaci
tance
d.Capaci
tanceandr
esi
stance
Ans:
a
6.I
ntheanal
ysi
soft
ransmi
ssi
onl
i
neonl
y--
--
--
--
--
--
-isconsi
der
ed.
a.Onephase
b.Twophase
c.Thr
eephase
Ans:
a
7.I
nanyt
ransmi
ssi
onl
i
neAD-BC =
a.1
b.0
c.2
ans:
a
8. I
nat
ransmi
ssi
onl
i
negener
ali
zedconst
ant
s--
--
-and-
--
-ar
eequal
a.BandD
b.AandB
c.AandC
d.AandD
ans:d
9.Thedi
mensi
onsofBandCar
erespect
ivel
y
a.ohm andSi
emens
b.ohm andohm
c.Si
emensandSi
emens
d.Si
emensandohm
ans:a
10.
Thel
i
neconst
ant
sofat
ransmi
ssi
onl
i
near
e--
--
--
--
--
--
--
--
a.l
umped
b.uni
for
mlydi
str
ibut
ed
c. i
tdependsont
hel
engt
hoft
hel
i
ne
d.somet
imel
i
mped
ans:b
11.
Thecapaci
tanceofat
ransmi
ssi
onl
i
nei
s3mi
croSi
emens.I
tscompl
ex
not
ati
onwillbe--
--
-
a.3x10-6<00
b.3x10-6<900
c. 3x10-9<00
d.3x10-9<900
ans:b
12.
Whent her
egul
ati
onisposi
ti
ve,
thenr
ecei
vi
ngendv
olt
age(
Vr)i
s--
-than
sendi
ngendvol
tage
a.mor
e
b.l
ess
c. 100%gr
eat
ert
han
d.Noneoft
heabov
e
ans:b
13.
--
---
--
--
--areusedtopr
ovi
decompensati
onattherecei
vi
ngendofa
transmissionli
nesoastoi
mproveit
sv ol
tagepr
ofil
e
a.Condenser
s
b.Resi
stor
s
c.React
ors
d.Condenser
s,r
esi
stor
sorr
eact
ors
14.
Thepowert
ransmi
ssi
oncapaci
tyofat
ransmi
ssi
onl
i
nei
s
a.Pr
opor
ti
onal
tot
ransmi
ssi
onv
olt
age
b.Pr
opor
ti
onal
tot
hesquar
eoft
ransmi
ssi
onv
olt
age
c.I
nver
sel
ypr
opor
ti
onal
tot
het
ransmi
ssi
onv
olt
age
d.I
nver
sel
ypr
opor
ti
onal
tot
hesquar
eoft
ransmi
ssi
onv
olt
age
Ans:
b
15.
Lineef
fi
ciencyi
ncr
easesf
or-
--
--
--
--
--
--
-tr
ansmi
ssi
onv
olt
ages
a.Hi
gher
b.Lower
c.Bot
h(a)and(
b)
d.Noneoft
hese
Ans:
a
16.Byincr
easi
ngthetr
ansmissi
onvolt
agedoubl
eofi
tsori
ginalval
ue,the
samepowercanbedespat
chedkeepingt
heli
nel
osses_____
______
____.
a.
Equaltoit
sor i
ginalvalue.
b.
Halfofit
soriginalvalue.
c.
Doubletheoriginal
v alue.
d.
One–f our
thoft heor i
ginalv
alue.
Ans:d
17.Thephenomenonofr i
seinv olt
ageatther
ecei
vi
ngendoft
heopenci
rcui
ted
orl
i
ghtlyloadedli
nei scall
edas
a.Ski
nef
fect
b.Pr
oxi
mit
yef
fect
c.Fer
rant
ief
fect
d.Seebeckef
fect
Ans:
c
18.
310km l
i
nei
sconsi
der
edas
a.Shor
t
b.Medium
c.Long
d.Cannotsay
Ans:c
19.
Powert
ransmi
tt
edwi
l
lbemaxi
mum when
a.Cor
onal
ossesar
emi
nimum
b.React
ancei
shi
gh
c.Sendi
ngendv
olt
agei
smor
e
d.Recei
vi
ngendv
olt
agei
smor
e
Ans:
c
20.
Whenli
veconductorofthepubl
i
cbr
eaksandt
ouchest
othegr
oundwhi
chof
thef
oll
owi
ngwillhappen]
a. Cur
rentwi
l
lfl
owt
otheear
th
b.Suppl
yvol
tagewi
l
lincr
ease
c.Nocur
rentf
lowt
hrought
heconduct
or
d.Noneoft
heabov
e
Ans:
a
21.Zer
ovol
tager
egul
ati
oni
spossi
bleonl
yfor
a.l
aggi
ngpowerf
act
or
b.l
eadi
ngpowerf
act
or
c.uni
typowerf
act
or
d.al
loft
heabov
e
Ans:
a
22.Fornominal
Tmet
hodmedi
um t
ransmi
ssi
onl
i
net
hev
aluesofA&D
const
ant
sare
a.
b.
c.
Ans:
a
23.Asi ngl
ephasel i
net
ransmits1000kW at10kVatap.
f.0.
85l
agging.I
thas
t
otal r
esi
stanceof2ohm, andinduct
iver
eact
anceof3ohm,Det
ermine
v
oltageregulat
ion
Tr
ansmi
ssi
onef
fi
ciency
a. 3.
78%,
97.
31%
b.3.
83%,
97.
31%
c. 2.
80%,
90.
31%
d.Dat
anotcor
rect
Ans:
b
24.An11kV, 3phaset r
ansmissionlinehasR=1.
5ohm andr eact
anceof4ohm
perphase,
cal
culatepercent
ager egul
ati
onoft
hel i
newhent ot
all
oadof5000
KVAat0.80p.
f.laggingissuppli
edat11KVatt herecei
vi
ngend.
a.16.62%
b.16.26%
c.3.87%
d.Cannotcal
cul
ate
Ans:b
25.An11kV, 3phaset r
ansmissionli
nehasR=1.5ohm andr eact
anceof4ohm
perphase,
cal
culatepercent
ageef f
ici
encyoft
helinewhentotall
oadof5000
KVAat0.80p.
f.laggingissuppli
edat11KVatt herecei
vi
ngend.
a.91.
78%
b.92.
87%
c.90.
87%
d.Cannotcal
cul
ate
Ans:b
26.
Findt
herecei
vi
ngimpedanceofatr
ansmi
ssi
onl
i
nehav
ingav
olt
ageof24V
andaconducti
oncur
rentof1.
2Ais
a)25.
2
b)22.
8
c)28.
8
d)20
Ans:
d
27.Totall
oadtransmi
tt
edthr
ougha3phaset
rans
missi
onlinei
s10,000kW at0.8power
2
fact
orlaggi
ng.TheIRlossesar
e900kW.Theef
fic
iencyoft
ransmi
ssi
onlineis
a.60%
b.90%
c.95%
d.99%.
Ans:b
28.Thechancesofcoronaar
emax
imum dur
ing
a.summerheat
b.wint
er
c.dryweather
d.humi
dweat her
.
Ans:d
29.Negl ect
inglos
sesinatr
ansmi
ssi
ons yst
em,i
fthevol
tagei
sdoubl
ed,f
ort
hesame
powertransmissi
on,t
hewei
ghtofconduct
ormater
ial
requi
redwi
l
lbe
a.fourti
mes
b.double
c.half
d.onefourth.
Ans:d
30.Thev ol
tageoft r
ans mi
ss i
oncanber egul
atedby
a.us
eoft apc hangingtransf
ormers
b.switchi
ngins huntcapac i
tor
sattherecei
vi
ngendduringheavyloads
c.useofs eri
escapac i
torstoneut
rali
zetheeff
ectofser
iesr
eactance
d.anyoft heabov emet hods.
Ansd
31.Inter
msofconstant
sA,B,CandDf
orshor
ttr
ansmi
ssi
onl
i
nes,whi
choft
he
fol
l
owingr
elat
ionisval
i
d?
a.A=B=1
b.B=D=0
c.A=C=1
d.C=0.
Ansd
32.Whi choft
hef
oll
owi
ngr
elat
ions
hipsi
snotval
i
dforshor
ttr
ansmi
ssi
onl
i
nes?
a.B=Z=C
b.A=D=1
c.I
s
=I r
d.Noneoft
heabove.
Ans.a
33.Asi
nglephaseli
netr
ansmit1000kW at10kVatap.f
.of0.
85lagging.Ithastot
al
l
oopresi
stanceof2ohm andinduct
iver
eact
anceof3ohm ,Vol
tager egul
ati
onof
t
heli
neis
a.A=D=0.
897<0.
139,
B=63.
74,
C =4X10-
6mhoperkm
b.A=D=0.
999<0.
139,
B=67.
74,
C =4X10-
6mhoperkm
c. A=D=0.
987<0.
139,
B=63.
74,
C =4X10-
6mhoperkm
d.Dat
ainsuf
fi
cient
Ans:
c
34.Al
i
neofwhatl
engt
hcanbecl
assi
fi
edasamedi
um t
ransmi
ssi
onl
ine?
a.90–100km
b.50–150km
c.150–200km
d.Abov
e200km
Ans:B
35.Whi
chamongt hefol
lowingmet
hodsar
eusedf
ort
hecal
cul
ati
onofsol
uti
onofa
medi
um t
ransmissi
online?
a.Endcondensermet
hod
b.OnlyTmet hod
c.Onlypmethod.
d.All
ofthese.
Ans:d
36.WhataretheAandDpar
amet
ersi
ncaseofmedi
um t
ransmi
ssi
onl
i
ne(
nomi
nalT
method)
?
a.A=D=1+(
YZ/2)
b.A=D=1+(
YZ/2)*Z
c.A=D=(
YZ/2)
d.A=D=(
YZ/2)*Y3
Ans:a
37.I
nthenomi
nal
pmet
hodwhi
chamongt
hesear
edi
vi
dedi
ntot
wohal
ves?
a.Seri
esimpedance
b.Shuntcapaci
tance
c.Both(A)and(B)
d.Noneoft
hese.
Ans: b
38.Whati
sthev
alueofBpar
amet
eri
ncaseofnomi
nalpmet
hod?
a.Y
b.Z
c.Y*(
1+YZ/4)
d.Z*(
1+YZ/4)
Ans:b
39.Whichoft hef oll

owi ngt ransmissi
onlinecanbeconsider
edasmedi um
tr
ansmi ssi
onl ine?
a)Tr
ans missionl ineofl engthupto600Km
b)Trans missionl ineofl engthupto500Km
c)Trans mi
ss i
onl i
neofl engt hupto200Km
d)Trans missionl ineofl engthupto80Km
Ans:c
Thetransmi ssionl i
neshavi nglengthmorethan80Km andl esst
han200Km are
consi
deredasmedi um t r
ans missi
onl i
nes.
Theiroper
ati
ngvolt
ageismorethanshor
t
tr
ansmissionlinesbutl esst hanlongtransmissi
onli
nes.
40.
Whi choft hefollowi
ngiscorr
ectoper
ati
ngvol
tagerangeformedium t
ransmi
ssi
on
li
nes.
a)Mor ethan765KV
b)Mor ethan400KV
c)Mor ethan20KV
d)Mor ethan132KV
Ans:c
Tr ansmissionlineshav
inglengt
hmor et
han80Km andl essthan200Km,
oper at
ingv ol
tagebetween20KVand100KVf al
li
nthecategoryofmedium
transmissionlines.
41.
Whati sthev alueofthec har
gingcurr
entf
lowingtoeart
hinmedium transmi
ssion
li
ne.
a)Ver yhigh
b)Medi um
c)Negl i
gibl
e
d)Noc apaci
tanc e
Ans:b
Owi ngtoappr eciabl
elengthandvolt
ageofthelinethechargi
ngcurr
entis
appr eci
ablei
nmedi um tr
ansmissi
onli
nes.Alsothecapaci
tanceef
fectcannotbe
ignoredinmedi um t
ransmiss
ionli
nes.
42.
Perf
ormanceofshorttr
ansmissi
onl
inesdependsonwhi
choft
hef
oll
owi
ng?
a)Resist
anceandCapac it
ance
b)Resist
anceandInduc t
ance
c)I
nductanceandCapac it
ance
d)Resist
ance,I
nductanceandCapacit
ance
Ans:b
43.
Perf
ormanceanal ysisofmedi um t
ransmissionl
ineisdone________
a)Byreactancediagr am
b)Bysymmet ri
calcomponentanal ysi
smet hod
c)Byneglecti
nglineinductance
d)Onperphas ebasi s
Ans:d
Perf
ormanceanal ysisofbalancetransmissionl
ineisdoneonly.Andisdoneon
perphasebas i
s.Nosy mmet r
icalc
omponentmet hodorreact
ancediagr
am
methodisrequir
edf orperf
or manceanalysis.
44.Whati sthev alueofshuntcapaci

tanceofmedi
um t r
ansmissionli
ne?
a)Veryhigh
b)Medium
c)Zero
d)Negli
gabl e
Ans:b
Lengthandoper at
ingv olt
ageofthemedium transmissi
onl inesaresuffi
ci
entl
y
l
argetoc auseunav oidabl
echar gi
ngcurr
entandther
eforecapacitanceeffectcannotbe
i
gnored.Capac itance eff
ectin medium t r
ansmi
ssi
on line i
sl ess than thatinlong
t
ransmissionl
ine.
45.
Inmedium tr
ansmi s
sionl
inethereceivi
ngendvoltagemaybegreat
erthan
sendingendv ol
tageduetoFerrantieff
ect.
a)True
b)False
Ans:b
Ferr
antief
fecthappenswhencapaci tanceeff
ecti
nmedium orl
ongt
ransmissi
on
li
nesbecomesgr eatert
haninductanceeffect
.Thi
shappensduri
ngl
owornol oad
peri
od.
46.Seri
esinduct
anceandseriesresi
stanceofmedium transmissi
onl i
nesaret
aken
as:
a)Dist
ri
butedandLumped
b)LumpedandDi st
ri
buted
c)Dist
ri
buted
d)Lumped
Ans:d
Expl
anati
on:Thes eri
esinduct
anceandr esi
stanceofmedi um tr
ansmi
ssi
on
l
inesaretakenaslumped.Thismakest heperf
ormanceanal ysiseasier
.
47.
Whichofthefol
lowingi
sli
keequi
valentci
rcui
tofmedium tr
ansmissi
online?
a)Seri
esRLCc i
rcui
t
b)RLCc ir
cui
tinpiefor
m
c)Seri
esRLci r
cuit
d)Paral
lelRLcir
cuit
Ans:b
Medium tr
ansmissi
onli
neshaveconsider
ableamountofinduct
ance,resist
ance
andshuntcapacit
ance.Medi
um t
ransmissi
onlinesar
erepresent
edasei t
herpi
e
for
m orasTf or
m.
48.Inmedium t
ransmi
ssi
onl
i
ness
huntcapaci
tancesar
econsi
der
edasl
umped.
a)t
rue
b)f
alse
Ansa:Incas eofmedium tr
ansmissi
onl i
nesthechargi
ngcurrenti
sunavoi
dable
butl
essthanthati
nlongtransmissi
onlines.Soitdoesnotcausemucherr
orin
cal
cul
ati
onsifshuntcapaci
tancesaretakenaslumped.
49.
I
d
Quest
ion Whi
choft
hef
oll
owi
ngmot
orhast
heconst
antspeed?
A Ser
iesmot
or
B Shuntmot
or
C I
nduct
ionMot
or
D Al
loft
heabov
e
Answer B
Mar
ks
Uni
t
I
d
Quest
ion ADCser
iesmot
ori
sbestsui
tabl
efordr
ivi
ng-
--
--
A Machi
net
ool
s
B Shear
sandpunches
C Cr
anesandhoi
sts
D Lat
hes
Answer C
Mar
ks
Uni
t
I
d
Quest
ion I
naDCser
iesmot
ori
ncr
easi
ngt
hel
oadcur
rentwi
l
l--
--
--
-
A I
ncr
easet
hespeed
B Decr
easet
hespeed
C Achi
evebet
tercommut
ati
on
D I
ncr
easet
hebackemf
Answer B
Mar
ks
Uni
t
I
d
Quest
ion TheDCmotor
,whichcanpr
ovi
del
owspeedv
ari
ati
onatf
ull
loadwi
thoutany
cont
rol
l
eri
s--
--
--
-
A Ser
iesmot
or
B Shuntmot
or
C Bot
hoft
heabov
e
D Noneoft
heabov
e
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Thed.
c.ser
iesmot
orshoul
dal
way
sbest
art
edwi
thl
oadbecause_
___
__
A i
twi
l
lnotdev
elophi
ghst
art
ingt
orque
B atnol
oad,
itwi
l
lrot
ateatdanger
ousl
yhi
ghspeed
C i
twi
l
lfai
ltost
art
D al
lar
etr
ue
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Thespeedofad.cser
iesmot
oratnol
oadi
s--
--
--
--
--
--
-
A zer
o
B v
eryl
ow
C danger
ousl
yhi
gh
D can’
tbesai
d
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Thedi
rect
ionofr
otat
ionofadcser
iesmot
orcanber
ever
sed-
--
--
--
--
-
A byi
nter
changi
ngt
hesuppl
yter
minal
s
B byi
nter
changi
ngt
hef
iel
dter
minal
s
C byi
nter
changi
ngt
hesuppl
yorf
iel
dter
minal
s
D noneoft
heabov
e
Answer B
Mar
ks
Uni
t
I
d
Quest
ion I
fadcmot
ori
sconnect
edacr
ossanacsuppl
y,t
hedcmot
orwi
l
l--
--
--
--
--
-
A r
unatal
owerspeed
B r
unati
tsnor
mal
speed
C bur
nast
heeddycur
rent
sint
hef
iel
dpr
oducesheat
D can’
tbesai
d
Answer C
Mar
ks
Uni
t
I
d
Quest
ion I
fthef
iel
dofadcshuntmot
ori
ssuddenl
yopened,
___
___
___
___
_.
A i
twi
l
lrunati
tsnor
mal
speed.
B t
hespeedoft
hemot
orwi
l
lber
educed.
C t
hemot
orwi
l
lcomet
ohaul
t.
D t
hespeedwi
l
lbeenor
mousl
yhi
gh,
andt
hemot
orwi
l
ldest
royi
tsel
f.
Answer D
Mar
ks
Uni
t
I
d
Quest
ion Whi
choneoft
hef
oll
owi
ngmot
orsi
susedi
nanel
ect
ri
clocomot
ive?
A Squi
rr
elCageI
nduct
ionmot
or
B DCser
iesmot
or
C DCshuntmot
or
D Noneoft
heabov
e
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Thear
mat
uret
orqueoft
hedcshuntmot
ori
spr
opor
ti
onal
to-
--
--
-
A ar
mat
urecur
rentonl
y
B f
iel
dfl
uxonl
y
C ar
mat
urecur
rentandf
iel
dfl
uxbot
h
D noneoft
heabov
e
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Theout
putpowerofanyel
ect
ri
cal
mot
ori
stakenf
rom t
he-
--
--
--
-
A Mot
orf
rame
B Coupl
i
ngmount
edont
heshaf
t
C Fi
eld
D Ar
mat
ure
Answer B
Mar
ks
Uni
t
I
d
Quest
ion I
fthebackemfi
nadcmot
ori
sreducedt
ozer
o,t
hent
hemot
or-
--
--
-
A st
arthunt
ing
B comet
ohaul
t
C mayev
ent
ual
l
ybur
n
D Can'
tsay
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Thedi
rect
ionoft
hear
mat
urecur
renti
nadcmot
ori
s--
--
--
--
--
--
--
A i
ndependentoft
hedi
rect
ionoft
hear
mat
ureemf
B t
hesameast
hegener
atedemf
C opposi
tet
othatofgener
atedemf
D noneoft
heabov
e
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Thedi
rect
ionofr
otat
ionofadcmot
orcanbepr
inci
pal
l
ydet
ermi
nedby
---
--
--
--
A Ri
ghthandt
humbr
ule
B Fl
emi
ng'
sri
ghthandr
ule
C Fl
emi
ng'
slef
thandr
ule
D Amper
e'sl
aw
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Athi
ckwirei
susedindcseri
esmotorf
iel
dwi
ndi
ngt
hant
hatoff
iel
dwi
ndi
ng
ofdcshuntmot
ort
o____
____
____
___
.
A Tocar
ryl
argel
oadcur
rent
B Tor
educet
her
esi
stance
C Tocr
eat
emor
efl
ux
D Bot
h(A)and(
B)
Answer D
Mar
ks
Uni
t
I
d
Quest
ion Anelectr
ict
rai
nempl
oyi
ngadcser
iesmotorisr
unningatthef
ixedspeed.
Whenasuddensli
ghtdr
opi
nthemainsv
oltageoccurs,
thi
swouldresul
tin-
--
--
-
-
--
--
--
---
--
-
A Ri
sei
nthespeedanddr
opi
nthecur
rent
B Ri
sei
nthespeedandr
isei
nthecur
rent
C Dr
opi
nthespeedandr
isei
nthecur
rent
D Dr
opi
nspeedwi
thcur
rentunal
ter
ed
Answer C
Mar
ks
Uni
t
I
d
Quest
ion ADCshuntmotori
sdr
ivi
ngaconstantt
orquel
oad.Oninser
ti
nganadditi
onal
r
esi
stancei
nthear
mat
ureci
rcui
t,t
hespeedofthemotorwil
l-
--
--
--
--
--
--
--
A bezer
o
B r
emai
nunchanged
C i
ncr
ease
D decr
ease
Answer D
Mar
ks
Uni
t 2
I
d
Quest
ion ADCser
iesmot
ori
sbestsui
tedf
ordr
ivi
ngcr
anesandhoi
stsbecause-
--
--
--
--
--
A i
tisr
uggedi
nconst
ruct
ionl
i
kei
nduct
ionmot
or
B i
tischeaperi
ncost
C i
tdev
elopshi
ghst
art
ingt
orque
D i
trunsatv
eryhi
ghspeed
Answer C
Mar
ks
Uni
t
I
d
Quest
ion
A
B
C
D
Answer
Mar
ks
Uni
t
I
d
Quest
ion I
naDCmot
or,
uni
dir
ect
ional
tor
quei
spr
oducedwi
tht
hehel
pof
___
___
__
A Thespeedofadcmot
orcanbecont
rol
l
edbyv
ary
ing_
___
___
__
B f
luxperpol
e
C r
esi
stanceofar
mat
ureci
rcui
t
D appl
i
edv
olt
age
Answer al
loft
heabov
e
Mar
ks D
Uni
t
I
d
Quest
ion Thecount
eremfi
nadcmot
or_
___
___
___
.
A Regul
atesi
tsar
mat
urev
olt
age
B Ai
dst
heappl
i
edv
olt
age
C Of
tenexceedst
hesuppl
yvol
tage
D Hel
psi
nener
gyconv
ersi
on
Answer D
Mar
ks
Uni
t
I
d
Quest
ion TheEb/
Vrat
ioofadcmot
ori
sani
ndi
cat
ionofi
ts-
--
--
--
--
--
-
A St
art
ingt
orque
B Runni
ngTor
que
C Speedr
egul
ati
on
D Ef
fi
ciency
Answer D
Mar
ks
Uni
t
I
d
Quest
ion TheTa/
Iagr
aphofadcser
iesmot
ori
sa_
___
___
___
_.
A St
rai
ghtl
i
net
hroughout
B Par
abol
athr
oughout
C Par
abol
afr
om nol
oadt
oov
erl
oad
D Par
abol
aupt
oful
ll
oadandast
rai
ghtl
i
neatov
erl
oads
Answer D
Mar
ks
Uni
t
I
d
Quest
ion Whenl
oadi
sremov
ed,
..
..
..
.mot
orwi
l
lrunatt
hehi
ghestspeed.
A Sl
i
pri
ngI
nduct
ionmot
or
B Squi
rr
elcageI
nduct
ionmot
or
C Shunt
D Ser
ies
Answer D
Mar
ks
Uni
t
I
d
Quest
ion I
nad.c.seri
esmot
or,
theel
ect
romagnet
ict
orquedev
elopedi
spr
opor
ti
onal
t
o__
_____.
A I
a
2
B I
a
3
C I
a
D a
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Adr
awbackofadcser
iesmot
ori
sit
s--
--
--
--
-
A hi
ghst
art
ingt
orque
B l
owst
art
ingt
orque
C const
antspeed
D speedr
unaway
Answer D
Mar
ks
Uni
t
I
d
Quest
ion Thespeedofad.
c.mot
ormaybei
ncr
easedby
___
___
___
_.
A decr
easi
ngt
heappl
i
edv
olt
age
B i
ncr
easi
ngt
hear
mat
urecur
rent
C decr
easi
ngt
hef
iel
dcur
rent
D i
ncr
easi
ngt
hef
iel
dcur
rent
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Theeff
ectofi
nsert
ingar
esi
stancei
nser
ieswi
tht
hef
iel
dwi
ndi
ngofashunt
motori
sto___
____
___.
A i
ncr
easet
hemagnet
icf
iel
d
B i
ncr
easet
hespeedoft
hemot
or
C r
educet
hemagnet
icf
iel
d
D decr
easet
hespeedoft
hemot
or
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Inadcshuntmot or;
theter
minalv
olt
ageishal
vedwhi
lethetor
queiskept
constant
.Theresul
ti
ngapproxi
matevar
iat
ioni
nspeed'N'andarmat
ure
curr
ent'Ia'wi
llbe____
A Ni
sconst
antbutI
aishal
ved.
B Ni
sdoubl
edwhi
l
eIai
shal
ved.
C Ni
sconst
antandI
aisdoubl
ed.
D Bot
hNandI
aar
edoubl
ed.
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Thetor
quei
na_
___
___
___
___
ispr
opor
ti
onal
tot
hesquar
eoft
hear
mat
ure
cur
rent
.
A DCshuntmot
or
B DCser
iesmot
or
C Separ
etel
yexci
tedmot
or
D Squi
rr
elcagei
nduct
ionmot
or
Answer B
Mar
ks
Uni
t
I
d
Quest
ion AscomparedtoshuntDCmotor
s,t
heser
iesDCmotorwi
llhavet
hehi
ghest
tor
quebecauseofi
tscompar
ati
vel
y__
___
____
___att
hest
art.
A Lowerar
mat
urer
esi
stance.
B Fewerser
iest
urns.
C Lar
gerar
mat
urecur
rent
.
D St
rongerser
iesf
iel
d.
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Machi
net
ool
sar
eat
ypi
cal
exampl
eof
___
___
___
___
.
A Var
iabl
etor
quel
oad
B Const
antt
orquel
oad
C Const
antpowerl
oad
D Bot
h(B)and(
C)
Answer D
Mar
ks
Uni
t
I
d
Quest
ion Whatwoul
dbeobser
vedi
fad.
c.shuntmot
ori
sst
art
edwi
thanopen-
cir
cui
ted
f
iel
d?
A Themot
ordoesnotpi
ckupspeedbutdr
awsasmal
lcur
rent
B Themot
ordoesnotpi
ckupspeedbutdr
awsi
slar
gecur
rent
C Themot
orpi
ckupf
astandacqui
resf
ull
speedwhi
l
edr
awi
ngsmal
lcur
rent
D Themot
orpi
cksupf
astandacqui
resf
ull
speedwhi
l
edr
awi
ngl
argecur
rent
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Whi
choft
hef
oll
owi
ngd.
c.mot
orshasappr
oxi
mat
elyconst
antspeed?
A ser
iesmot
or
B shuntmot
or
C I
nduct
ionmot
or
D al
loft
heabov
e
Answer B
Mar
ks
Uni
t
I
d
Quest
ion I
fthesuppl
yvolt
agei
nashuntmot
ori
sincr
eased,
whi
choft
hef
oll
owi
ngwi
l
l
bedecr
eased?
A st
art
ingt
orque
B f
ull
loadspeed
C f
ull
loadcur
rent
D noneoft
heabov
e
Answer D
Mar
ks
Uni
t
I
d
Quest
ion I
fad.
c.ser
iesmot
ori
sst
art
edatnol
oad,
itwi
l
l__
___
___
_.
A notst
art
B st
artatnomi
nal
speed
C r
unatv
eryhi
ghr
.p.
m.
D r
unwi
th.
excessi
venoi
se
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Whati
sthef
unct
ionofcommut
atoroft
hed.
c.mot
or?
A Topr
oduceuni
dir
ect
ional
tor
que
B t
oconv
ert
sal
ter
nat
ingemfi
nducedi
ntoDCv
olt
age
C t
oimpr
oveef
fi
ciencyofmachi
ne
D t
oobt
ainhi
ghst
art
ingt
orque
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Ad.c.shuntmot
ori
srunningatl
i
ghtl
oad.I
fthef
iel
dwi
ndi
ngget
ssuddenl
y
opened,whatwi
l
lhappen?
A mot
orwi
l
lst
opi
nst
ant
ly.
B mot
orwi
l
ltendt
opi
ckuphi
ghspeed.
C mot
orwi
l
ltakeheav
yinputcur
rent
.
D mot
orwi
l
lmakemechani
cal
noi
se.
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Ad.
c.ser
iesmot
or_
___
___
___
A mayst
opi
fthef
iel
dget
sopened.
B i
snotsui
tabl
eforhi
ghst
art
ingt
orque.
C shoul
dal
way
sbest
art
edonl
oad.
D al
way
srunsatconst
antspeed.
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Whi
choft
hef
oll
owi
ngcomponent
sisani
dent
it
yofad.
c.mot
or?
A ar
mat
ure
B sl
i
pri
ngs
C commut
ator
D f
iel
dwi
ndi
ng
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Aser
iesmot
orhas_
___
___
_.
A wi
del
yvar
yingspeed.
B hi
ghspeedathi
ghl
oadsandl
owspeedatl
owl
oads.
C appr
oxi
mat
elyconst
antspeedatal
ll
oads.
D bot
h(A)and(
B)
Answer A
Mar
ks
Uni
t
I
d
Quest
ion Themot
orusedi
ncent
ri
fugal
andr
eci
procat
ingpumpsi
s--
--
--
--
A D.
Cser
ies
B D.
C.shunt
C I
nduct
ionMot
or
D Noneoft
heabov
e
Answer B
Mar
ks
Uni
t
I
d
Quest
ion --
--
---
--
--
ispref
erabl
yusedf
orspeedcont
rol
ofDCshuntmot
ort
oobt
ainspeed
belowr at
edspeed.
A Fl
uxcont
olmet
hod
B Rheost
ati
ccont
rolmet
hod
C Appl
i
edv
olt
agecont
rolmet
hod
D Bot
h(B)and(
C)
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Tappedf
iel
dmet
hodi
susedf
orcont
rol
l
ingspeedof-
--
--
--
--
--
--
A C.shuntmot
D. or
B D.
C.ser
iesmot
or
C Squi
rr
elcagei
nduct
ionmot
or
D Sl
i
pri
ngi
nduct
ionmot
or
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Whi
choft
hef
oll
owi
ngappl
i
cat
ionsr
equi
reshi
ghst
art
ingt
orque?
A Ai
rbl
ower
B Locomot
ive
C Lat
hemachi
ne
D Cent
ri
fugal
pump
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Whi
cht
ypeofD.
C.mot
orwi
l
lbepr
efer
redf
ormachi
net
ool
s?
A Squi
rr
elcagei
nduct
ionmot
or
B Sl
i
pri
ngi
nduct
ionmot
or
C Shuntmot
or
D Ser
iesmot
or
Answer C
Mar
ks
Uni
t
I
d
Quest
ion St
art
ersar
eusedf
orD.
C.mot
orsbecause_
___
___
___
__.
A t
hesemot
orsar
enotsel
f-
star
ti
ng.
B t
hesemot
orshav
ehi
ghst
art
ingt
orque.
C l
argear
mat
urecur
rentatst
artr
equi
rest
ober
educed.
D i
ner
ti
aatst
arti
stobeov
ercome.
Answer C
Mar
ks
Uni
t
I
d
Quest
ion I
nDCshuntmot
orasl
oadi
sreduced,
___
___
___
___
_
A t
hespeedwi
l
lbedr
ast
ical
l
yreduced.
B t
hespeedwi
l
lbeabr
upt
lyi
ncr
eased.
C t
hespeedpr
act
ical
l
yremai
nsconst
ant
.
D cannotbesai
d
Answer C
Mar
ks
Uni
t
I
d
Quest
ion I
ncaseofDCshuntmot
orst
hespeedi
sdependentonbacke.
m.f
.onl
y
because.
..
..
..
..
.
A ar
mat
uredr
opi
snegl
i
gibl
e.
B backe.
m.f
.isequal
toar
mat
uredr
op.
C f
luxi
spr
act
ical
l
yconst
anti
nthesemot
ors.
D f
luxi
spr
opor
ti
onal
toar
mat
urecur
rent
.
Answer C
Mar
ks
Uni
t
I
d
Quest
ion At
hreepoi
ntst
art
eri
sconsi
der
edsui
tabl
efor_
___
___
_.
A DCshuntmot
or
B DCser
iesmot
or
C Sl
i
pri
ngi
nduct
ionmot
ors
D Squi
rr
rel
cagei
nduct
ionmot
or
Answer A
Mar
ks
Uni
t
I
d
Quest
ion Al
thoughbackemfopposest
heappl
i
edv
olt
age,
it_
___
___
___
___
_.
A i
ncr
easest
hemot
ort
orque
B cannotequal
theappl
i
edv
olt
age
C decr
easesmot
orspeed
D hel
psf
lowofar
mat
urecur
rent
Answer B
Mar
ks
Uni
t
I
d
Quest
ion I
nducedbackemfi
nadcmot
oract
sas_
___
___
__r
egul
ator
.
A cur
rent
B v
olt
age
C ef
fi
ciency
D t
orque
Answer A
Mar
ks
Uni
t
I
d
Quest
ion Asl
oadi
sappl
i
edt
oadcshuntmot
or,
its_
___
___
___
___
.
A t
orquedev
elopeddecr
eases
B count
eremfi
ncr
eases
C ar
mat
urecur
renti
ncr
eases
D f
iel
dcur
renti
ncr
eases
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Whenadcser
iesmot
orr
unsathi
ghspeed,
___
___
___
__.
A i
tsar
mat
urecur
renti
ssmal
l
B i
tdev
elopsl
esst
orque
C i
tsEbi
slar
ge
D al
loft
heabov
e
Answer D
Mar
ks
Uni
t
I
d
Quest
ion Thear
mat ur
ecur r
entdr
awnbyadcmot
ori
sgi
venbyI
a
=V Raonl
ywhent
he
motor
..
..
..
..
..
..
..
..
..
A r
unsatf
ull
load
B r
unsathal
fload
C i
sst
ati
onar
y
D noneoft
heabov
e
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Thear
mat
urepowerdev
elopedbyadcmot
or_
___
___
___
___
.
A VI
a
B EbI
a
2
C IR
a a
D Al
loft
heabov
e
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Condi
ti
onf
ormaxi
mum powerdev
elopedbyadcmot
ori
s__
___
___
___
__.
A Eb=V
B Eb=V 2
C Eb>V
D Eb<V
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Asl
oadi
sappl
i
edt
oadcser
iesmot
or,
the_
___
___
___
___
.
A Count
eremfi
ncr
eases
B Ar
mat
urecur
renti
ncr
eases
C Ser
iesf
iel
dcur
rentdecr
eases
D Ar
mat
urecur
rentdecr
eases
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Whichoft
hef
oll
owi
ngmot
ordev
elopst
hehi
ghestt
orquebet
weennol
oadand
f
ull
load?
A Squi
rr
elcagei
nduct
ionmot
or
B Sl
i
pri
ngi
nduct
ionmot
or
C Ser
iesmot
or
D Shuntmot
or
Answer D
Mar
ks
Uni
t
I
d
Quest
ion Thear
mat
uret
orquedev
elopedbyadcshuntmot
or_
___
___
___
__.
A decr
easeswi
thi
ncr
easi
ngl
oad
B di
rect
lydependsonappl
i
edv
olt
age
C v
ari
esdi
rect
lywi
thar
mat
urecur
rent
D i
sindependentofspeed
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Whi
choft
hef
oll
owi
ngdcmot
ori
swel
lsui
tedf
oroper
ati
ngl
i
neshaf
ts?
A Compoundmot
or
B Separ
atel
yexci
tedmot
or
C Ser
iesmot
or
D Shuntmot
or
Answer D
Mar
ks
Uni
t
I
d
Quest
ion Becauseofi
tshi
ghst
art
ingt
orque,
aser
iesmot
ori
susedf
or_
___
___
___
_.
A l
argepr
esses
B cent
ri
fugal
pumps
C machi
net
ool
s
D el
ect
ri
ctr
ains
Answer D
Mar
ks
Uni
t
I
d
Quest
ion DCser
iesmot
ori
sbestsui
tedf
or_
___
___
___
___
_.
A l
athemachi
nes
B r
api
dtr
ansi
tsy
stems
C dr
il
li
ngmachi
nes
D bl
ower
s
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Mot
orst
art
ersar
eessent
ial
for
___
___
___
___
.
A pr
event
ingf
usebl
owi
ng
B st
art
ingt
hemot
or
C accel
erat
ingt
hemot
or
D av
oidi
ngt
heexcessi
vest
art
ingcur
rent
Answer D
Mar
ks
Uni
t
I
d
Quest
ion Fort
hesamer
ati
ng,
DC_
___
___
__mot
orhast
hehi
ghestst
art
ingt
orque.
A shunt
B compound
C Bot
h(A)&(
B)
D ser
ies
Answer D
Mar
ks
Uni
t
I
d
Quest
ion Adcmot
ori
sst
il
lusedi
nindust
ri
alappl
i
cat
ionsbecausei
t__
___
___
___
__.
A i
scheap
B i
ssi
mpl
einconst
ruct
ion
C pr
ovi
desf
inespeedcont
rol
D r
equi
resl
owmai
ntenance
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Thev
alueofbackemfi
nadcmot
ori
smax
imum at
___
___
___
___
_.
A nol
oad
B f
ull
load
C hal
fful
ll
oad
D atst
art
Answer A
Mar
ks
Uni
t
I
d
Quest
ion Ther
unni
ngspeedofadcser
iesmot
ori
sbasi
cal
l
ydet
ermi
nedby
___
___
___
__.
A ar
mat
urer
esi
stance
B f
iel
dexci
tat
ion
C l
oad
D noneofabov
e
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Thedeci
dingfact
orintheselect
ionofadcmot
orf
orapar
ti
cul
arappl
i
cat
ioni
s
i
ts__
____
_____
charact
erist
ics.
A speed-
-t
orque
B speed-
-ar
mat
urecur
rent
C t
orque-
-ar
mat
urecur
rent
D noneofabov
e
Answer A
Mar
ks
Uni
t
I
d
Quest
ion Fort
hesamer
ati
ng,
___
___
___
mot
orhast
hel
eastst
art
ingt
orque.
A DCcompound
B DCshunt
C DCser
ies
D dat
ainsuf
fi
cient
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Theonlydisadv
antageoffi
eldcontr
olmet
hodf
orcont
rol
l
ingt
hespeedofadc
shuntmethodisthati
t__
____
_ _
____
_.
A adv
ersel
yaf
fect
scommut
ati
on
B gi
vesspeedl
owert
hant
henor
mal
speed
C i
nvol
vespowerl
oss
D needsal
arger
heost
at
Answer A
Mar
ks
Uni
t
I
d
Quest
ion Byfluxcont
rolmet
hodofspeedcont
rol
ofdcshuntmot
or,
wecanobt
ain
speeds.
..
..
..
..
A bel
owt
henor
mal
speedonl
y
B abov
ethenor
mal
speedonl
y
C abov
easwel
lasbel
owt
henor
mal
speed
D baseduponappl
i
cat
ionsr
equi
rement
Answer B
Mar
ks
Uni
t
I
d
Quest
ion Ther
heost
ati
cspeedcont
rol
met
hodi
sver
y__
___
___
___
.
A ef
fi
cient
B economi
cal
C unsui
tabl
eforr
api
dlychangi
ngl
oads
D sui
tabl
eforget
ti
ngspeedsabov
ethenor
mal
Answer C
Mar
ks
Uni
t
I
d
Quest
ion Byputt
ingcont
rol
lerresi
stanceinser
ieswi
tht
hear
mat
ureofadcmot
or,
we
canobtai
nspeeds..
..
..
..
..
..
..
..
..
..
.
A abov
ethenor
mal
speedonl
y
B bel
owt
henor
mal
speedonl
y
C abov
easwel
lasbel
owt
henor
mal
speed
D basedonappl
i
cat
ionsr
equi
rement
Answer B
Mar
ks
Uni
t
I
d
Quest
ion A220Vdcshuntmotordev
elopsator
queof54N-m atanarmat
urecur
rentof
0A.Thetor
quepr
oducedwhenthearmat
urecur
rentbecomes20A
i
s__
____
____
.
A 27N-
m
B 54N-
m
C 08N-
m
D Noneoft
hese
Answer C
Mar
ks 2
Uni
t
I
d
Quest
ion A220Vdcshuntmotorhasanarmat
ureresi
stanceof0.2ohm andfiel
d
r
esit
anceof0ohm.Themotordr
aws5Aat500r pm atnoload.Thespeed
whenthemotordr
aws52Aatratedv
olt
ageis_____
______
.
A 563.
9rpm
B 500r
pm
C 435.
73r
pm
D Noneoft
hese
Answer C
Mar
ks 2
Uni
t
I
d
Quest
ion A250Vdcshuntmotorrunsat000r pm atnol
oadandtakes8A.Thetotal
ar
matur
eandshuntf
iel
dr esi
tancesare0.2ohm and250ohm r
espect
ivel
y.
Themot
orwi
l
lrunat
___
___
__r
pm whi
l
etaki
ng50Aatr
atedv
olt
age.
A 033.
4rpm
B 966.
2rpm
C 000r
pm
D Noneoft
hese
Answer B
Mar
ks 2
Uni
t
I
d
Quest
ion A460Vdcseriesmotorr
unsat500rpm t
aki
ngacurr
entof40A.I
fnowthe
l
oadisr
educedandthemotort
akes30A,theper
cent
agechangei
narmatur
e
t
orquei
s__
____
_ _
___
.
A 25.
00%
B 33.
33%
C 43.
75%
D Noneoft
hese
Answer C
Mar
ks 2
Uni
t
I
d
Quest
ion A220Vshuntmachi nehasanarmatureresist
anceof0.5ohm.I
fthef
ulll
oad
armat
urecur
renti
s20A, thei
nducedemf swhent hemachi
neact
sas( i
)motor
and(i
i
)gener
atorare___
____,
___
_____
__respecti
vely
.
A 230V,
20V
B 20V,
230V
C 220V,
220V
D 220V,
230V
Answer B
Mar
ks 2
Uni
t
I
d
Quest
ion A440V, shuntmotorhasarmaturer
esist
anceof0.8ohm andfi
eldr
esi
stance
of200ohm.Thear matur
ecurrentwhil
edeli
ver
inganoutputof7.
46KW at85
per
centeffi
ciencyi
s__
____
__.
A 4.
75A
B 9.
95A
C 7.
75A
D 22.
5A
Answer C
Mar
ks 2
Uni
t
I
d
Quest
ion A250V,dcshuntmot orhasarmat
ureandfi
eldresi
stancesof0.
06ohm and
00ohm r
espect
ivel
y.Thetot
alarmat
urepowerdevel
opedwhi l
etaki
ng25KW
i
nputi
s__
____
__.
A 24.
79KW
B 26.
25KW
C 25.
2KW
D 23.
8KW
Answer D
Mar
ks 2
Uni
t
I
d
Quest
ion Theloadcur
rentofad.
c.seri
esmot
ori
s50A,whensuppl
yingofaful
ll
oad
tor
que.I
fthecurr
enti
sreducedt
o25A,t
het
orquewil
lbe_
__ _
___
__.
A sameasf
ull
loadt
orque
B 50%off
ull
loadt
orque
C 25%off
ull
loadt
orque
D cannotbedeci
ded
Answer C
Mar
ks 2
Uni
t
I
d
Quest
ion Ad. c.shuntmotorrunsatnoloadspeedof40r.
p.m.Atful
lload,armature
reactionweakensthemainfluxby5%whereasthearmatur
eci r
cuitvol
tage
dropsby0%.Themot orful
ll
oadspeedinr.p.
m.is_
____
____
__ _
A 000
B 080
C 200
D 203
Answer B
Mar
ks 2
Uni
t
I
d
Quest
ion Aseparatelyexci
teddcmot ortakesanarmatur
ecurrentof0Aat480V.The
aramt
ureci rcui
tresi
stanceis0. 2ohm.Themachi nehas6pol esandthe
aramt
urei slapconnectedwit
h864conductors.Thefluxperpol
ei s0.
05Wb.
Theoperatingspeedofthemotoris__
___
____
.
A 697r
pm
B 232r
pm
C 636r
pm
D Noneoft
hese
Answer C
Mar
ks 2
Uni
t
I
d
Quest
ion Adcshuntmotordev
elopsacount
eremfof250Vat500rpm.Thearamt
ure
t
orquedevel
opedwhi
ledrawi
ng50Aarmaturecur
renti
s__
___
___
___
__.
A .
32N-
m
B .
99N-
m
C 79.
58N-
m
D Noneoft
hese
Answer C
Mar
ks 2
Uni
t
I
d
Quest
ion Thedevelopedtorqueofa220V,4-
pol
eseri
esmotorwit
hwavewound800
conduct
ors;taki
ng45Af r
om mai
nsis_
___
____
___
.Thefl
uxperpol
eis25mWb.
A 94.
53N-
m
B 43.N-
m
C 286.
2N-
m
D Noneoft
hese
Answer C
Mar
ks 2
Uni
t
I
d
Quest
ion A220Vdcshuntmot orrunsat500rpm whent
hear
maturecur
renti
s50A f
or
gi
venload.Thearmatureresi
stancei
s0.
2ohm.Thespeedwhenthetor
quei
s
doubl
edis..
..
..
..
..
..
..
.
A 476r
pm
B 490r
pm
C 50r
pm
D Noneoft
heabov
e
Answer A
Mar
ks 2
Uni
t
El
ect
ri
cal
Machi
ne1
Uni
t5&6Thr
eePhaseI
nduct
ionMot
ors
MCQQuest
ions
Q.
1 Choosecor
rectr
elat
ionbet
weenr
otorcopperl
oss(
Wcu)
andgappower(
Pg)of
t
hreephaseI
M.
a) Wcu=s.
Pg
b) Pg
Wcu=
S
c) Wcu=s2.
Pg
d) Wcu=(
1-s)*Pg
Q.
2 Choosecor
rectr
elat
ionbet
weenmechani
calpowerdev
eloped(
Pmd)andgap
Pg)oft
power( hreephaseI
M.
a) Pmd=(
s)*Pg
b) Pmd=s2*Pg
c) Pmd=(
1-s)*Pg
d) Pg
Pmd=
S
Q.
3 I
nduct
ionmot
oref
fi
ciencyi
s
a) Pg
η=
Pi
b) P
η= sh
Pi
c) P
η= md
Pi
MmcoeSEEl
ect
ri
cal
1
El
ect
ri
cal
Machi
ne1
d) P
η= sh
Pmd
Q.
4 Thecondi
ti
onf
ormaxi
mum t
orquei
nIMi
s
a) R2=SX20
b) R2R2= =X20
91-
c) R2=s2X20
d) R2=(
1-S)*X20
Q.
5 Whichoft
hef
oll
owi
ngst
atementi
scor
recti
ncaseofconst
ruct
ionoft
hree
phaseI
M?
a) St
atori
sst
ati
onar
ypar
t.
b) At
hreephaseACsuppl
yisgi
vent
orot
or
c) At
hreephaseACsuppl
yisgi
vent
ost
ator
d) Bot
ha)andc)
Q.
6 Themai
nfunct
ionofst
atorf
ramei
s
a) Tosuppor
tst
atorcor
eandf
iel
dwi
ndi
ng
b) I
tact
sascov
eri
ngandpr
ovi
depr
otect
iont
orot
or
c) I
tgi
vesmechani
cal
str
engt
htoal
li
nnerpar
tsofI
M.
d) Al
loft
heabov
e
Q.
7 Thewi
ndi
ngwoundont
hreephaseI
Miscal
l
edas….
.
a) Rot
orwi
ndi
ng
b) Fr
amewi
ndi
ng
MmcoeSEEl
ect
ri
cal
2
El
ect
ri
cal
Machi
ne1
c) Fi
eldwi
ndi
ng
d) Cor
ewi
ndi
ng
Q.
8 Thedi
ff
erencebet
weensy
nchr
onousspeedandspeedofr
otori
scal
l
edas….
.
a) Sl
i
p
b) Sl
ipspeed
c) Rot
orspeed
d) Fi
l
edspeed
Q.
9 I
ncaseofI
M,whi
chonei
str
uer
elat
ionbet
weensy
nchr
onousspeedandspeed
ofr
otor
?
a) NS=Nr
b) NS<Nr
c) NS ≈Nr
d) NS>Nr
Q.
1 Whenmot
ori
satr
estcondi
ti
on,
sli
pis
0
a) 1
b) -
1
c) 0
d) Equal
tosy
nchr
onousspeed
Q.
1 Thecor
rectr
elat
ionbet
weensy
nchr
onousspeedandspeedofr
otori
s
1
MmcoeSEEl
ect
ri
cal
3
El
ect
ri
cal
Machi
ne1
a) NS=(
1-S)
Nr
b) Nr=(
1-S)
NS
c) Nr=S*NS
d) NS=Nr
Q.
1 At
hreephase,
4pol
e,440V,
50HzI
Mrunswi
thsl
i
p4%.Fi
ndr
otorspeedNr.
2
a) Nr=1440
b) Nr=1500
c) Nr=60
d) Nr=18750
Q.
1 Athreephase,4pol
e,440V,50HzI
Mrunswi
thsl
i
p4%.Fi
ndf
requencyofr
otor
3 cur
rent.
a) f
requencyofr
otorcur
rent=4Hz.
b) f
requencyofr
otorcur
rent=2Hz.
c) f
requencyofr
otorcur
rent
=1Hz.
d) f
requencyofr
otorcur
rent
=50Hz.
Q.
1 A6poleI
Mi sconnect
edt
o50Hzsuppl
y.I
tisr
unni
ngataspeedof970r
pm.
4 Fi
ndsy
nchr
onousspeed
a) NS =1000
b) NS=1500
c) NS=1455
d) NS=970
MmcoeSEEl
ect
ri
cal
4
El
ect
ri
cal
Machi
ne1
Q.
1 Rot
oroft
hreephaseI
Misusual
l
ymadeupof
5
a) Copper
b) Car
bon
c) Al
umi
num
d) CastI
ron
Q.
1 A4-polethr
ee-phasei
nduct
ionmotorhasasy
nchr
onousspeedof25r
ev/
s.The
6 f
requencyofthesuppl
ytothest
atori
s:
a) 50
b) 100
c) 25
d) 12.
5
Q.
1 I
ninduct
ionmot
ort
heuni
tofsl
i
pis
7
a) r
pm
b) Met
erpersecond
c) Uni
tless
d) r
adi
an
Q.
1 Athree phase,4 pol
e,50 Hzstarconnect
ed I
M runni
ng on f
ulll
oad has
8 mechani
calpowerdevel Pmd)i
oped( s52778.552W.Findgappower(Pg)
.The
r
otorspeedi
s1440r
pm.
a) Pg=54977.
86W
MmcoeSEEl
ect
ri
cal
5
El
ect
ri
cal
Machi
ne1
b) Pg=60000W
c) Pg=52278.
552W
d) Pg=2199.
114W
Q.
1 Athree phase,4 pol
e,50 Hzst arconnected I
M runni
ng on f
ulll
oad has
9 mechani
calpowerdevel
oped(Pmd)is52778.
552W.r ot
orcopperl
oss(Wcu)
.The
r
otorspeedi
s1440r
pm.
a) Wcu=54977.
86W
b) Wcu=60000W
c) Wcu=52278.
552W
d) Wcu=2199.
114W
Q.
2 Wi
ththei
ncr
easei
nsuppl
yvol
tage,t
hest
art
ingt
orqueofa3phasei
nduct
ion
0 mot
or
a) decr
eases
b) Remai
nssame
c) i
ncr
eases.
d) Noneofabov
e
Q.
2 Theshaf
tofani
nduct
ionmot
ori
smadeof
1
a) hi
ghspeedst
eel
b) st
ainl
essst
eel
c) car
bonst
eel
d) casti
ron
MmcoeSEEl
ect
ri
cal
6
El
ect
ri
cal
Machi
ne1
Q.
2 I
nani
nduct
ionmot
or,
no-
loadt
hesl
i
pisgener
all
y
2
a) l
esst
han1%
b) 1.
5%
c) 2%
d) 4%
Q.
2 I
nmedi
um si
zedi
nduct
ionmot
ors,
thesl
i
pisgener
all
yar
ound
3
a) 0.
04%
b) 0.
4%
c) 4%
d) 14%
Q.
2 I
nasqui
rr
elcagemot
ort
hei
nducede.
m.f
.is
4
a) dependentont
heshaf
tloadi
ng
b) dependentont
henumberofsl
ots
c) sl
ipt
imest
hest
andst
il
le.
m.f
.inducedi
nther
otor
d) noneoft
heabov
e
Q.
2 Fordr
ivi
nghi
ghi
ner
ti
aloadsbestt
ypeofi
nduct
ionmot
orsuggest
edi
s
5
a) Sl
ipr
ingt
ype
b) squi
rr
elcaget
ype
c) anyoft
heabov
e
MmcoeSEEl
ect
ri
cal
7
El
ect
ri
cal
Machi
ne1
d) noneoft
heabov
e
Q.
2 Whatwil
lhappeni ft
herel
ati
vespeedbet
weent
her
otat
ingf
luxofst
atorand
6 r
otoroft
heinduct
ionmot
oriszer
o?
a) Thesl
i
poft
hemot
orwi
l
lbe5%
b) Ther
otorwi
llnotr
un
c) Ther
otorwi
l
lrunatv
eryhi
ghspeed
d) Thet
orquepr
oducedwi
l
lbev
eryl
arge
Q.
2 Thet
orqueofar
otori
nani
nduct
ionmot
orunderr
unni
ngcondi
ti
oni
smaxi
mum
7
a) att
heuni
tval
ueofsl
i
p
b) att
hezer
oval
ueofsl
i
p
c) atthev al
ueofthesl
ipwhi
chmakesr
otorr
eact
anceperphaseequalt
othe
resi
stanceperphase
d) att
hev
alueoft
hesl
i
pwhi
chmakest
her
otorr
eact
ancehal
foft
her
otor
Q.
2 Sl
i
pri
ngsar
eusual
l
ymadeof
8
a) copper
b) car
bon
c) phosporbr
onze
d) al
umi
nium
Q.
2 A3-phase440V,
50Hzi
nduct
ionmot
orhas4%sl
i
p.Thef
requencyofr
otore.
m.f
.
9 wi
ll
be
a) 200Hz
MmcoeSEEl
ect
ri
cal
8
El
ect
ri
cal
Machi
ne1
b) 50Hz
c) 2Hz
d) 0.
2Hz
Q.
3 Theef
fi
ciencyofani
nduct
ionmot
orcanbeexpect
edt
obenear
ly
0
a) 60t
o90%
b) 80t
o90%
c) 95t
o98%
d) 99%
Q.
3 Thenumberofsl
i
pri
ngsonasqui
rr
elcagei
nduct
ionmot
ori
susual
l
y
1
a) t
wo
b) t
hree
c) f
our
d) Zer
o
Q.
3 Thest
art
ingt
orqueofasqui
rr
el-
cagei
nduct
ionmot
ori
s
2
a) l
ow
b) sameasf
ull
-l
oadt
orque
c) negl
i
gibl
e
d) sl
i
ght
lymor
ethanf
ull
-l
oadt
orque
Q.
3 St
ar-
del
tast
art
ingofmot
orsi
snotpossi
blei
ncaseof
MmcoeSEEl
ect
ri
cal
9
El
ect
ri
cal
Machi
ne1
a) si
ngl
ephasemot
ors
b) v
ari
abl
espeedmot
ors
c) l
owhor
sepowermot
ors
d) hi
ghspeedmot
ors
Q.
3 I
ncaseoft
hei
nduct
ionmot
orst
het
orquei
s
4
a) i
nver
sel
ypr
opor
ti
onal
to(
V*sl
i
p)
2
b) di
rect
lypr
opor
ti
onal
to(
sli
p)
c) i
nver
sel
ypr
opor
ti
onal
tosl
i
p
d) di
rect
lypr
opor
ti
onalt
osl
ip
Q.
3 Whichofthefol
l
owingmethodsi
seasi
l
yappl
i
cabl
etocont
rolt
hespeedoft
he
5 squi
rr
el-
cagei
nduct
ionmot
or?
a) Bychangi
ngt
henumberofst
atorpol
es
b) Rot
orr
heost
atcont
rol
c) Byoper
ati
ngt
womot
orsi
ncascade
d) Byi
nject
inge.
m.f
.int
her
otorci
rcui
t
Q.
3 Rot
orr
esi
stancecont
rol
met
hodofspeedcont
rol
isusedf
or
6
a) squi
rr
el-
cagei
nduct
ionmot
orsonl
y
b) sl
ipr
ingi
nduct
ionmot
orsonl
y
c) bot
h(a)and(
b)
d) noneoft
heabov
e
MmcoeSEEl
ect
ri
cal
10
El
ect
ri
cal
Machi
ne1
Q.
3 Ani
nduct
ionmot
ori
s
7
a) sel
f-
star
ti
ngwi
thzer
otor
que
b) sel
f-
star
ti
ngwi
thhi
ght
orque
c) sel
f-
star
ti
ngwi
thl
owt
orque
d) non-
sel
f-
star
ti
ng
Q.
3 Themaxi
mum t
orquei
nani
nduct
ionmot
ordependson
8
a) f
requency
b) r
otori
nduct
iver
eact
ance
c) squar
eofsuppl
yvol
tage
d) al
loft
heabov
e
Q.
3 I
nthr
ee-
phasesqui
rr
el-
cagei
nduct
ionmot
ors
9
a) r
otorconduct
orendsar
eshor
t-
cir
cui
tedt
hroughsl
i
pri
ngs
b) r
otorconduct
orsar
eshor
t-
cir
cui
tedt
hroughendr
ings
c) r
otorconduct
orsar
ekeptopen
d) r
otorconduct
orsar
econnect
edt
oinsul
ati
on
Q.
4 DOLst
art
ingofi
nduct
ionmot
orsi
susual
l
yrest
ri
ctedt
o
0
a) l
owhor
sepowermot
ors
b) v
ari
abl
espeedmot
ors
MmcoeSEEl
ect
ri
cal
11
El
ect
ri
cal
Machi
ne1
c) hi
ghhor
sepowermot
ors
d) hi
ghspeedmot
ors
Q.
4 I
nani
nduct
ionmot
ort
her
elat
ionshi
pbet
weenst
atorsl
otsandr
otorsl
otsi
sthat
1
a) st
atorsl
otsar
eequal
tor
otorsl
ots
b) st
atorsl
otsar
eexactmul
ti
pleofr
otorsl
ots
c) st
atorsl
otsar
enotexactmul
ti
pleofr
otorsl
ots
d) noneoft
heabov
e
Q.
4 Sl
i
pri
ngmot
ori
srecommendedwher
e
2
a) speedcont
rol
isr
equi
red
b) f
requentst
art
ing,
stoppi
ngandr
ever
singi
srequi
red
c) hi
ghst
art
ingt
orquei
sneeded
d) al
labov
efeat
uresar
erequi
red
Q.
4 I
fa3-phasesuppl
yisgi
vent
othest
atorandr
otori
sshor
tci
rcui
tedr
otorwi
l
l
3 mov
e
a) I
ntheopposi
tedi
rect
ionast
hedi
rect
ionoft
her
otat
ingf
iel
d
b) i
nthesamedi
rect
ionast
hedi
rect
ionoft
hef
iel
d
c) i
nanydi
rect
iondependi
nguponphasesequenceofsuppl
y
d) none
Q.
4 Thespeedcharact
eri
sti
csofaninducti
onmotorcl
osel
yresembl
ethespeedl
oad
4 char
acter
ist
icsofwhi
chofthefol
lowingmachi
nes
MmcoeSEEl
ect
ri
cal
12
El
ect
ri
cal
Machi
ne1
a) D.
C.ser
iesmot
or
b) D.
C.shuntmot
or
c) uni
ver
sal
mot
or
d) noneoft
heabov
e
Q.
4 A3-
phasesl
i
pri
ngmot
orhas
5
a) doubl
ecager
otor
b) woundr
otor
c) shor
t-
cir
cui
tedr
otor
d) anyoft
heabov
e
Q.
4 Thest
art
ingt
orqueofa3-
phasesqui
rr
elcagei
nduct
ionmot
ori
s
6
a) t
wicet
hef
ull
loadt
orque
b) 1.
5ti
mest
hef
ulll
oadt
orque
c) equal
tof
ull
loadt
orque
d) Hal
ftof
ull
loadt
orque
Q.
4 I
nat
hree-
phasei
nduct
ionmot
or
7
a) i
ronl
ossesi
nst
atorwi
l
lbenegl
i
gibl
eascompar
edt
othati
nrot
or
b) i
ronl
ossesi
nmot
orwi
l
lbeneg¬l
i
gibl
eascompar
edt
othati
nrot
or
c) i
ronl
ossesi
nst
atorwi
l
lbel
esst
hant
hati
nrot
or
d) i
ronl
ossesi
nst
atorwi
l
lbemor
ethant
hati
nrot
or
MmcoeSEEl
ect
ri
cal
13
El
ect
ri
cal
Machi
ne1
Q.
4 Theshapeoft
het
orque/
sli
pcur
veofi
nduct
ionmot
ori
s
8
a) par
abol
a
b) hy
per
bol
a
c) r
ect
angul
arpar
abol
a
d) st
rai
gthl
i
ne
Q.
4 Thef
rameofani
nduct
ionmot
ori
susual
l
ymadeof
9
a) si
l
iconst
eel

b) Casti
ron
c) al
umi
nium
d) br
onze
Q.
5 Whi
choft
hef
oll
owi
ngcomponenti
susual
l
yfabr
icat
edoutofsi
l
iconst
eel
?
0
a) Bear
ings
b) Shaf
t
c) St
atorcor
e
d) Al
loft
heabov
e
Q.
5 A500kW,3-
phase,440v
olt
s,50Hz,
A.C.induct
ionmot
orhasaspeedof960
1 r
.p.
m.onf
ulll
oad.Themachi
nehas6poles.Thesli
poft
hemachinewi
llbe
a) 0.
01
b) 0.
02
c) 0.
03
MmcoeSEEl
ect
ri
cal
14
El
ect
ri
cal
Machi
ne1
d) 0.
04
Q.
5 Whatwil
lhappeni ft
herel
ati
vespeedbet
weent
her
otat
ingf
luxofst
atorand
2 r
otoroft
heinduct
ionmot
oriszer
o?
a) Thesl
i
poft
hemot
orwi
l
lbe5%
b) Ther
otorwi
llnotr
un
c) Ther
otorwi
l
lrunatv
eryhi
ghspeed
d) Thet
orquepr
oducedwi
l
lbev
eryl
arge
MmcoeSEEl
ect
ri
cal
15
Q- Power transformers are designed to have maximum efficiency at
A-nearly full load
B-70% full load
C-50% full load
D-No load
Answer- A
Q- Hysteresis loss in a transformer varies as Bmax = maximum flux density
A-Bmax
B-Bmax1.6
C-Bmax1-83
D-None
Answer-B
Q- During short circuit test iron losses are negligible because
A-the current on secondary side is negligible
B-the voltage on secondary side does not vary
C-the voltage applied on primary side is low
D-Full load current is not supplied to transformer
Answer-C
Q- In an actual transformer the iron loss remains practically
constant from no load to full load because
A-value of transformation ratio remains constant
B-permeability of transformer core remains constant
C-core flux remains practically constant
D-primary voltage remains constant
Answer-C
Q- The full-load copper loss of a transformer is 1600 W. At half-load, the
copper loss will be
A-6400 W
B-1600 W
C-800W
D-400W
Answer-D
Q- Iron loss of a transformer can be measured by
A-low power factor wattmeter
B-unity power factor wattmeter
C-frequency meter
D-any type of wattmeter
Answer-A
Q- The efficiency of a transformer, under heavy loads, is comparatively low
because
A-copper loss becomes high in proportion to the output
B-iron loss is increased considerably
C-voltage drop both in primary and secondary becomes large
D-secondary output is much less as compared to primary input
Answer-A
Q- The o/p current corresponding to maximum efficiency for a
transformer having copper loss of 100 watt and equivalent resistance
reffered to secondary of 0.25 ohm is ampere
A-20
B-25
C-5
D-400
Answer-A
Q- The maximum efficiency of a 100 kVA transformer having iron loss of
900W and F.L. cu loss of 1600 W occurs at
...........kVA
A-56.3
B-133.3
C-75
D-177.7
Answer-C
Q- The all day efficiency of the transformer depends primarily on
A-its copper loss
B-the amount of load
C-the duration of the load
D-Both B & C
Answer-D
Q- Iron loss for a transformer is 400 W. If the transformer is working at
its maximum efficiency then copper loss will be
A-1600 W
B-200 W
C-400W
D-800W
Answer-C
Q- Auto-transformer makes effective saving on
copper losses , when
A-Its transformation ratio is < 1
B-Its transformation ratio is >= 1
C-Its transformation ratio is > 1
D-Its transformation ratio is ≈ 1
Answer-D
Q- When an auto-transformer is preferred to a conventional 2-
winding transformer?
A-Where ratio of transformation is low
B-Where large number of secondary taps are needed
C-Where it is required to electrically isolate the two windings
D-Because it is much safer to use an auto-transformer
Answer-A
Q- Which of the following factor governs the saving in Cu achieved by
converting 2-winding transformer into an auto- transformer?
A-Load on the secondary
B-Size of the transformation core
C-voltage transformation ratio
D-Magnetic quality of core material
Answer-C
Q- The KVA rating of an ordinary 2- winding transformer increased when
connected as an auto-transformer because
A-transformation ratio is increased
B-secondary voltage is increased
C-Energy is transferred both inductively and conductivity
D-secondary current is increased
Answer-C
Q- In step-down auto-transformer power transferred inductively is
A-I1 ( V1 – V2 )
B-I1 ( V2 – V1 )
C-I1 ( I1 – I2 )
D-V1 ( I2 – I1)
Answer-A
Q- In step-down auto-transformer power
transferred conductively is
A-V2 I2
B-V2 I1
C-V1 I1
D-V1 I2
Answer-B
Q- 110 V, 50 Hz single phase supply is needed from a 220 V 50 Hz source.
Determine the ratios of weights of copper needed in a two- winding
transformer and an autotransformer employed for the purpose
A-2:1
B-1:2
C-3:1
D-1:3
Answer-A
Q- An auto-transformer having a transformation ratio of 0.8 supplies a
load of 3 kW . The power transferred conductively from primary to
secondary is ---------- kW
A-0.6
B-2.4
C-1.5
D-0.27
Answer-B
Q- A single phase transformer has rating of 15 KVA , 600/120 V . It is
reconnected as an auto –transformer to supply at 720 V from a 600 V
primary source . The maximum load it can supply is
A-90 KVA
B-18 KVA
C-15 KVA
D-12 KVA
Answer-A
Q- A 400/100 V, 10 kVA two-winding transformer is reconnected to auto-
transformer across a suitable voltage source. The maximumrating of such
an arrangement could be
A-50 kVA
B-15 kVA
C-12.5 kVA
D-8.75 kVA
Answer-C
Q- In case of a transformer, the EMF induced in a primary winding is due to
A-Self induction
B-Mutual induction
C-Both A and B
D-None of these
Answer-A
Q- In case of a transformer, the primary & secondary windings
are wound on a same limb, so as to reduce
A-Self induction
B-Mutual induction
C-Leakage reactance
D-None of these
Answer-C
Q- In case of which of the following equipment, the EMF induced is due to
static induction?
A-DC motor
B-Transformer
C-DC generator
D-None of these
Answer-B
Q- Which of the following is /are the types of transformer ?
A-Core type
B-Shell type
C-Berry type
D-All of these
Answer-D
Q- The losses obtained in Open Circuit Test are
A-Eddy current losses
B-Hysteresis losses
C-Copper losses
D-Both A & B
Answer-D
Q- The Open Circuit & Short Circuit Tests are carried out, so as to find
A-Iron losses & Copper losses
B-Efficiency
C-Regulation
D-All of these
Answer-D
Q- The No Load primary current of 1φ transformer is normally of full
load current.
A-2 to 5 %
B-12 %
C-15 %
D-20%
Answer-A
Q- Which of the following, is not a basic element of a transformer?
A-Primary winding
B-Secondary winding
C-Core
D-Mutual flux
Answer-D
Q- In a relation to transformer, 17:1 indicates that
A-There are 17 turns on primary and 1 turn on secondary
B-Secondary voltage is 1/17th of primary voltage
C-Primary current is 17 times greater than the secondary
current
D-For every 17 turns on primary, there is 1
turn on secondary
Answer-D
Q- The equivalent resistance (R1e) referred
to primary side is
A-R2 + (R2 . k 2)
B-R2 + (R1 / k 2)
C-R1 + (R2 . k 2)
D-R1 + (R2 / k 2)
Answer-D
Q- The copper saving in case of auto-transformer is
A- k x weight of 2 winding transformer
B- B-(1-k) x weight of 2 winding transformer
C- k / weight of 2 winding transformer
D- D- Weight of 2 winding transformer / k
Answer-A
Q- The voltage regulation is positive for load.
A-Inductive
B-Capacitive
C-Resistive
D-Both A & C
Answer-D
Q- The No Load primary current is the vector sum
of
A-Loss component of No Load current
B-Magnetizing component of No Load current
C-Both A & B
D-None of these
Answer-C
Q- The primary and secondary induced EMF's E1 and E2 in a
two winding transformer are always
A-Equal in magnitude
B-Anti-phase with each other
C-In phase with each other
D-Determined by nature of load on secondary
Answer-C
Q- Cylindrical windings are preferred for core
type transformers as
A-Easy for maintenance
B-Easy for cooling
C-Both A & B
D-None of these
Answer-C
Q- According to Faraday's Law, as long as there is
change in flux, induced emf persists.
A-First
B-Second
C-Third
D-None
Answer-A
Q- Bushings are made with --.
A-Conducting Materials
B-Semiconducting materials
C-Insulating materials
D-Magnetic materials
Answer-C
Q- A 800 kVA, single phase transformer has a voltage ratio of 6600/5000
volt. If Emf per turn = 8 Volt, calculate number of turns on high voltage and
low voltage side.
A-825, 625,
B-625, 825
C-600, 800
D-500, 660
Answer-B
Q- A 100 KVA, 2200/440 V transformer has R1 = 0.3 ohm; X1 = 1.1 ohm;
R2 = 0.01 ohm and X2 = 0.035 ohm. Equivalent impedance of transformer
referred to the primary is
A-2.05 Ω
B-2.005 Ω
C-2.5 Ω
D-2.005 Ω
Answer-A
Q- OC test is to be conducted on 1kVA, 230/115 V, 50 Hz single
phase transformer. Suggest suitable range of voltmeter.
A-0-75 V
B-0-150 V
C-0-300 V
D-0-500 V
Answer-B
Question - SC test is to be conducted on 1kVA, 230/115 V, 50 Hz single
phase transformer. Suggest suitable range of voltmeter.
A-0-75 V
B-0-150 V
C-0-250 V
D-0-300 V
Answer-A
Q- The % decrease in hysteresis loss of a 1-phase transformer working on
200, 50Hz supply, when operated on 160V,40 Hz supply would be
A-32
B-20
C-25
D-40
Answer-B
Q-OC test data for 200/400 V, 50 Hz single phase transformer is 200 V,
0.8 A, 80 W. The exciting circuit resistance is.
A-500 Ω
B-400 Ω
C-1000 Ω
D-160 Ω
Answer-A
Q-The flux through the core of a transformer is 0.06 wb. The cross-
sectional area of the core is 400 cm2. The operating flux density in the core
is,
A-1.5T
B-1.35T
C-1.45T
D-1.57T
Answer-A
Q- In a transformer the magnetic coupling between the primary
and secondary winding can be increased by
A-increasing the number of turns
B-using soft material for winding
C- using the magnetic core of low reluctance
D-using transformer oil of better quality
Answer-C
Q-A 3 ph transformer has its primary is connected in delta &
secondary connected in star. Secondary to primary turns ratio per
phase is 5. For a primary voltage of 400 v, the secondary voltage
would be
A-2000v
B-80v
C-3464v
D-80√3 v
Answer-C
Q -Two single phase transformers with equal turns have
impedance of (0.5+j3) Ω & (0.6 + j 10) Ω with respect to the
secondary. If they operate in parallel , how will they share a load of
100 kw at 0.8 p.f. lagging
A-50 kw, 50kw
B-62kw, 38 kw
C-78.2kw, 21.8Kw
D-85.5kw, 14.5kw
Answer-C
Q -Two single phase transformers A & B rated at 250 kVA each
are operated in parallel on both sides. Percentage impedance for
both A & B are (1+j6) and (1.2+j4.8) respectively. Compute the
load shared by each when the total load is 500kVA at 0.8 pf
lagging
A-200KW, 300KW
B-225KW, 275KW
C-275KW , 225KW
D-250KW, 250KW
Answer-B
Q -A 500 kVA transformer with 1% resistance & 5 % reactance is
connectd in pareallel with a 250 kVA transformer with 1.5%
resistance & 4% reactance. The secondary voltage of each
transformer is 400 volt on no load. Find how they share a load of
750 kVA at a p.f. of 0.8 lagging
A-300KW, 450KW
B-375KW, 375KW
C-280KW , 470KW
D-470KW, 280KW
Answer-D
Q -Two single phase transformers A & B of equal voltage ratio are
running in parallel and supply a load of 1000A at 0.8 p.f lag. The
equivalent impedance for both A & B are (2+j3) and (2.5+j5) ohms
respectively. Compute the current supplied by transformers A & B.
A-609.7 A, 392.6 A
B-392.6 A, 609.7 A
C-500A, 500A
D-Nona of these
Answer-A
Q -In a Delta -Delta connection, if one of the transformer winding is
open, the capacity will reduce to:
A-66.67%
B-57.74%
C-50%
D-33.33%
Answer-B
Q -A 3-phase transformer over a bank of 3-single phase
transformers of equal rating, has the advantage of:
A-Low cost
B-Less weight
C-Occupation of less space
D-All the above
Answer-D
Q -In which of the transformer, the
tertiary winding is used:
A-Delta-delta
B-Star-star
C-Delta-star
D-Star-delta
Answer- B
Q -The magnetizing current in a
transformer is rich in
A-3rd harmonic
B-5th harmonic
C-7th harmonic
D-11th harmonic
Answer-A
Q -Scott connections are used for.
A-Single phase to three phase transformation
B-Three phase to single phase transformation
C-Three phase to two phase transformation
D-Any of the above
Answer-C
Q - For successful parallel operation of two single phase
transformers, the most essential condition is that their:
A-Percentage impedances
are equal
B-Polarities are properly
connected
C-Turn-ratios are exactly
equal
D-kVA ratings are equal
Answer-B
Q -In conversion of 3-phase to 2-phase supply with T connection,
the transformation ratio of the teaser will be times to that of main
transformer:
A-1.732
B-1.15
C-0.866
D-Unity
Answer-C
Q -Two transformers of identical voltages but different capacities
are operated in parallel, for satisfactory load sharing:
A-Impedances should be equal
B-Per unit impedance must be equal
C-per unit impedance and X/R ratio must be equal
D-Impedance and X/R ratio must be equal
Answer-C
Q -Which of the following 3-phase connection of a transformer
causes interference with the neighboring communication lines:
A-Delta-star
B-Star-delta
C-Star-star
D-Delta-star
Answer-C
Q -Which of the following transformer connection will
give highest secondary voltage
A-Delta primary, delta secondary
B-Delta primary, star secondary
C-Star primary, delta secondary
D-Star primary, star secondary
Answer-B
Q -Two transformers connected in parallel with wrong polarities
results
A-Dead Short-circuiting of the secondaries
B-Power factor of one of the transformers is leading while that of
the other lagging
C-Transformers having higher copper losses
will have negligible core losses
D-Loading of the transformers not in
proportion to their kVA ratings
Answer-A
Q -If three transformers in a Δ − Δ are delivering their rated load
and one transformer is removed, then overload on each of the
remaining transformers is ... percent.
A-66.7
B-173.2
C-73.2
D-58
Answer-C
Q -. In a three-phase Y-Y transformer connection,
neutral is fundamental to the
A-suppression of harmonics
B-passage of unbalanced currents due
to unbalanced loads
C-provision of dual electric service
D-balancing of phase voltages with respect to line voltages.
Answer-A
Q -Which of the following connections is best suited for 3-phase, 4-
wire service ?
A-Δ – Δ
B-Y− Y
C-Δ –Y
D-Y− Δ
Answer-C
Q -Transformers operating in parallel will share the load depending
upon their
A-Leakage reactance B-Rating C-Efficiency. D-Percentage
impedance. Answer-D Question-Two transformers, with equal
rating & negligible excitation current, connected in parallel share
the load in the ratio of their kVA ratings only, if their pu impedance
(based on their own kVA )are
A-Equal
B-In the inverse ratio of their
ratings
C-In the direct ratio of their
ratings
D-Pure reactive
Answer-A
Q - In Scot –connections the teaser transformer operates on 0.866
of its rated
A-Impedance
B-Current
C-Voltage
D-power
Answer-C
Q -Keeping in view the requirement of parallel operation which of
the 3-phase connections given follows are possible
A-Delta-delta to Delta –star
B-Delta-delta to Star – delta
C-Star – star to Delta-delta
D-Delta –star to Star – delta
Answer-C
Q - Three phase transformer connections most commonly used
are:
A-Δ – Δ
B-Y− Y
C-Δ –Y and Y− Δ
D-Δ – Δ and Δ –Y
Answer-C
Q -In the star-star connection of 3 ph transformer , the phase shift
between the line voltage & phase voltage is
…… degrees on both primary & secondary sides
A-0
B-30
C-60
D-90
Answer-B
Q -In Y-Y connection, the angular displacement between primary &
secondary voltage is ......................................................... Degrees
A-0
B-90
C-180
D-120
Answer-A
Q -Y-Y connection is used only
A-As distribution transformer
B-At the receiving end
C-For power measurement
D-For small current high voltage transformers
Answer-D
Q -The Y-Y connection works satisfactorily
only if the load is
A-Y type
B-Δ type
C-Unbalanced
D-Balanced
Answer-D
Q -For Y-Y connection we have to face a problem called … in
unbalanced load
A-Neutral shift
B-Earth shift
C-Earth leakage
D-None of these
Answer-A
Q -connection can be used for both balanced & unbalanced
load
A-Y-Y
B-Δ - Δ
C-Δ - Y
D-Y- Δ
Answer-B
Q -The ... Configuration of 3 ph transformer can be used for serving
the three phase power equipment as well
as the single phase lighting loads
A-Y-Y
B-Δ - Δ
C-Δ - Y
D-Y- Δ
Answer-C
Q -For Δ- Y connection with transformation ratio
K=Vph2/Vph1 the line voltage VL2 is equal to
A-VL1/K
B-K VL1
C-VL1/√3K
D-√3K VL1
Answer-D
Q -The main application of …. Transformer is the substation end of
the transmission line, where the voltage has to be stepped down
A-Y-Y
B-Δ - Δ
C-Δ - Y
D-Y- Δ
Answer-D
Q -In star – delta transformer with
transformation ratio K=Vph2/Vph1 IL2= ………
A-√3K IL1
B-IL1/√3K
C-IL1/K
D-√3 IL1 /K
Answer-D
Q -…….. is used when 3 ph load is too small to use a
full 3 phase transformer bank
A-Y-Y
B-Δ - Δ
C-Δ - Y
D-open delta
Answer-D
Q -V-V connection can be obtained by
removing one transformer from
A-Y-Y
B-Δ - Δ
C-open delta
D-Y- Δ
Answer-B
Q -The two secondary voltages of transformer are……..degree
phase shifted with each other in scott connection
A-30
B-60
C-90
D-120
Answer-C
Q -The transformers (single phase or three phase) are connected
in … in oreder to supply load that is higher than the rating of one
transformer
A-Series
B-Cascade
C-Cascade
D-Parallel
Answer-D
Q - The essential condition for successful parallel operation of two
three phase transformers ….
A-Polarities of the transformer should be same
B-Phase sequence of the transformer should be same
C-Phase displacement between primary and secondary line
voltages of the transformer should be same
D-All the above
Answer-D
Q -If all other requirements for parallel operations of the
transformers are fulfilled, which one of the following pairs of three-
phase transformers with the given VECTOR GROUPS, can be
operated is parallel?
A-Yd1 and YY0
B-Yd1 and DY 1
C-DD6 and DY 1
D-Dd0 and DY 11
Answer-B
Q -Two 3 phase transformers are to be connected for parallel
operation. Which one of the arrangements will be impossible?
A-Transformer A: primary Y:
secondary Y Transformer
B: primary Δ: secondary Δ
B-Transformer A: primary Δ:
secondary Y Transformer
B: primary Δ: secondary Δ
C-Transformer A: primary Y:
secondary Δ
Transformer B: primary Δ:
secondary Y
D-Transformer A: primary
Δ: secondary Δ
Transformer B: primary Δ: secondary Δ
Answer-B
Q -In the statement , “In star /delta transformer, there exists a
phase difference of “X” between the corresponding phases of
primary and secondary “Y”. “X” and “Y” stand respectively for
A-60 and voltages.
B-60 and currents.
C-30 and voltages
D-30 and currents.
Answer-C
Q -Three single phase 11,000/220 V transformer are connected to
form 3-phase transformer bank. High voltage side is connected in
star, and low voltage side is connected in delta. What are the
voltage ratings and the turn ratio of 3-phase transformer ?
A-19,052/220 V ,50
B-19,052/381 V, 50
C-11,000/381 V, 50
D-11000/220 V, 50
Answer-A
Q -The magnetizing current in transformer is rich in
rd t harmonic
A-3 h
harmonic Answer-A
th harmonic
C-7 B-
5
t
h
harmonic
D-
13
Q -In which of the 3 ph transformer connection, phase
displacement between HV & LV line voltage is 180 degree
A-Yy0, Dd0
B-Yy6, Dd6
C-Dy1, Yd1
D-Dy11, Yd11
Answer-B
displacement between HV & LV line voltage is 30 degree lagging
A-Yy0, Dd0
B-Yy6, Dd6
C-Dy1, Yd1
D-Dy11, Yd11
Answer-C
displacement between HV & LV line voltage is 30 degree leading
A-Yy0, Dd0
B-Yy6, Dd6
C-Dy1, Yd1
D-Dy11, Yd11
Answer-D
Q -Average power which V-V bank operate is when load is
at unity Power factor
A-86.6%
B-73.3%
C-66.67%
D-None of these
Answer-A
Q -In conversion of 3-phase to 2-phase supply with T connection,
the transformation ratio of the teaser will be times to that of main
transformer:
A-1.732
B-1.15
C-0.866
D-Unity
Answer-C
Q -In Yy 0 connection, the angular displacement between primary &
secondary line voltage is.................................................. Degrees
A-0
B-90
C-180
D-120
Answer-A
Q -In Δy 11 connection the angular displacement in degrees
between primary & secondary line voltage is… degree
A-0
B-30 lagging
C-30 leading
D-120
Answer-C
Q - The.... Configuration of 3 ph transformer can be used for
serving the three phase power equipment as
well as the single phase lighting loads
A-Y-Y
B-Δ - Δ
C-Δ - Y
D-Y- Δ
Answer-C
Q -For Δ- Y connection with transformation ratio
K=Vph2/Vph1 the line voltage VL2 is equal to
A-VL1/K
B-K VL1
C-VL1/√3K
D-√3K VL1
Answer-D
Q -Which three-phase connection can be used in a transformer to
introduce a phase difference of 30 degree between its output and
corresponding input line voltages?
A-Star-star
B-Star-Delta
C-Delta-Delta
D-Delta-Zigzag
Answer-B
Q -Two transformers of identical voltages but of different
capacities are operating in parallel .for satisfactory load sharing
A-Impedances must be equal.
B-Per unit Impedances must be equal.
C-Per unit Impedances and X/R ratio must be equal.
D-Impedances and X/R ratio must be equal.
Answer-C
Q -Star/delta connection for three phase distribution
transformers is very common for
A-Large rating, low voltage transformers
B-Small rating, high voltage transformers
C-Power supply transformers
D-Distribution transformers
Answer- C
Q -Most suitable connection of three phase
distribution transformers is.
A-delta/ delta
B-delta/ star
C-Star/ delta
D-Star/ Star
Answer-B
Q -In Scott-connected transformers,50%tapping
should be provided on the
A-Primary of teaser transformers
B-Primary of main transformers
C-Secondary of main transformers
D-Secondary of teaser transformers
Answer-B
Q -For converting a three phase balanced system into a two
phase system ,the number of transformers needed are,
A-One three phase transformer
B-Three single phase transformers
C-Two single phase transformers
D-One single phase transformer
Answer-C
Q -Which of the following two, three phase transformers can be
operated in parallel
A-Δ/Δ and Δ⥾
B-Y/Y and Y/Δ
C-Y/Y and Δ/Δ
D-None of these combination
Answer-C
Q -Three single phase transformer, each with a 10 kVA rating are
connected in a closed delta arrangement. If one transformer is
taken out, the output capacity of the system will be
A-20 kVA
B-8.66 kVA
C-17.32 kVA
D-10 kVA
Answer -C
Q -Three number of 10:1 transformers are connected in star-delta
to supply a load at 230 V.The supply voltage of this transformer
must be
A-2300 V
B-4000 V
C-23 V
D-40 V
Answer- B
Q -Three units of 1:5 transformers are connected in delta-star to
supply a 3 phase load from a 400 V, 3 phase source. The line
voltage on the load side is
A-1000 V
B-80 V
C-3464 V
D-803 V
Answer-C
Q -The current in HV winding of a 25kVA, 6600/400 V, 50Hz, 3
phase D-Y transformer, at full load is
A-1.26 A
B-3.72 A
C-2.18 A
D-0.72 A
Answer-A
Q -The current in HV winding of a 25kVA, 6600/400 V,50Hz,3 phase
Y-D transformer, at full load is
A-1.26 A
B-3.72 A
C-2.18 A
D-0.72 A
Answer-C
Q -The current in LV winding of a 25kVA, 6600/400 V,50Hz,3
phase Y-D transformer, at full load is
A-36 A
B-20.78 A
C-65.32 A
D- 40.2 A
Answer-B
Q -The current in HV winding of a 20kVA, 2200/220 V,50Hz,3 phase
D-D transformer, at full load is
A-3.03 A
B-5.25 A
C-10.5 A
D-None of these
Answer-A
Q -The current in LV winding of a 20kVA, 2200/220 V,50Hz,3
phase D-D transformer, at full load is
A-52.48 A
B-30.30 A
C-26.24 A
D-None of these
Answer-B
Q. in lap winding, the number of brushes is always
Ans= same as the number of poles
Q.the insulating material used between the commutator segments is normally?
Ans= mica
Q.the armature torque of the D.C shunt motor is proportional to
Ans= armature current only
Q.the direction of rotation of a D.C . series motor can be changed by?
Ans= a) interchanging field terminals b) interchanging supply terminals c) none d) any of the
above
Q.what will happen if the back emf of a DC motor vanishes suddenly
Ans= armature will burn
Q.in D.C shunt motors as load is reduced
Ans= the speed will remain almost constant
Q.the type of D.C motor used for shears and punches is
Ans= shunt motor
Q.three point starter can be used for?
Ans= both shunt and compound motor
Q.if a D.C shunt motor is working at full load and if shunt field circuit suddenly opens
Ans= is will result in excessive speed, possibly destroying armature due to excessive
centrifugal stresses
Q.the speed of a D.C shunt motor can be increased by
Ans= increasing the resistance in field circuit
Q.which D.C motor will be preferred for machine tools
Ans= shunt motor
Q. the commutator segments are connected to the armature conductors by means of
Ans= copper lugs
Q.when the armature of a D.C motor rotates emf induced if;
Ans= back emf
Q.the armature core of a D.C generator is usually made of
Ans= silicon steel
Q.the function of pole shoes in the case of D.C machine is
Ans= to discharge all the above functions
Q.in a D.C generator the number of mechanical degrees and electrical degrees will be the
same when
Ans= number of poles is 2
Q.in a D.C generator the magnetic neutral axis coincides with the geometrical neutral axis,
when:
Ans= there is no load on the generator
Q.in a D.C machine stray loss is the sum of
Ans= iron loss and mechanical los
Q.a DC generator can be considered as
Ans=rectifier
Q.compensating windings are used in DC generators
Ans= to neutralize the cross-magnetizing effect of the armature reaction
Q.laminations of core are generally made of
Ans=silicon steel
Q.in DC generator the cause of rapid brush wear may be
Ans= a) rough commutator surface b) severe sparking c) imperfect contact d) any of the
above
Q. in lap winding, the number of brushes is always
Ans=same as the number of poles
Q.for a DC generator when the number of poles and the number of armature conductors is
fixed, then which winding will give the higher emf?
Ans=wave winding
Q.iron losses in a DC machine are independent of variations in
Ans= load
Q.in DC generators current to the external circuit from armature is given through
Ans= commutator
Q.brushes of dc machines are made of
Ans= carbon
Q.if B is the flux density, I the length of conductor and v the velocity of conductor , then
induced emf is given by
Ans= BIv
Q.the material for commutator brushes is generally
Ans= carbon
Q.the insulating material used between the commutator segments is normally
Ans= mica
Q.eddy currents are induced in the pole shoes of a DC machine due to
Ans= relative rotation between field, and armature
Q.the armature of DC generator is laminated to
Ans= reduce eddy current loss
Q.in case of DC machine winding number of commutator segments is equal to
Ans= number of armature coils
Q.the function of poles shoes in the case of DC machine is?
Ans= a)to reduce the reluctance of the magnetic path b) to support the field coil. C) to spread
out the flux to achieve uniform flux density d) to discharge all the above function
Q.the demagnetizing component of armature reaction in a DC generator
Ans= reduces generator emf
Q.magnetic field in a DC generator is produced by
Ans= a) electromagnets b) permanent magnets c) both a and b d) non of these
Q.the emf generated by shunt wound DC generator is E. now while pole flux remains
constant, if the speed of the generator is doubled, the emf generated will be
Ans= 2E
Q.satisfactory commutation of DC machines requires
Ans= a) brushes should smoothly run in the holders b) smooth, concentric commutator
properly undercut c) brushes should be of proper grade and size d) all of these
Q.the resistance of armature winding depends on
Ans= a) number of conductors b) length of conductor c) cross-sectional area of the conductor
d) all of these
Q.the field coils of DC generator are usually made of
Ans= copper
Q.the commutator segments are connected to the armature conductors by means of
Ans= copper lugs
Q.in a commutator
Ans= mica is harder than copper
Q.in DC generators the pole shoes are fastened to the pole core by,.
Ans= counter sunk screws
Q.of
Ans= lines of force
Q.thumb points towards
Ans=direction of motion of conductor, if forefinger points along the lines of flux,
Q.a transformer transforms?
Ans= current and voltage
Q.a transformer transfers…. Without change
Ans= frequency
Q.though the load changes, …. Losses remain same
Ans=a)hysteresis b) copper c) both a & b d) eddy current
Q.normally open circuit test is carried out on… winding, keeping ….. winding open.
Ans=LV, HV
Q.the no load primary current of 10 transformer is normally …… of full load current
Ans= 2 To 5 %
Q.in case of a transformer, the emf induced In a secondary winding is due to
Ans= mutual induction
Q.which of the following is not basic element of a transformer?
Ans= mutual flux
Q.the hysteresis loss is proportional to
Ans= a) volume of magnetic material b) flux density c) frequency d) all of these
Q.in an ideal transformer:
Ans=a) core has no losses b) core has infinite permeability c) windings have no resistance d)
all of these
Q.the eddy current loss is proportional to
Ans= a) flux density b) frequency c) thickness of material d) all of these
Q.the hysteresis loss is given by
Ans= Ph=Kh. Bm1.6.f.V watt
Q.in case of a transformer, the emf induced in a primary winding is due to:
Ans= self induction
Q.normally short circuit test is carried out on….. winding, keeping …. Winding shorted.
Ans=HV,LV
Q.the main purpose of using core, in a transformer is to
Ans= reduce reluctance of magnetic circuit
Q.the rating of transformer is given in
Ans= KVA
Q.the hysteresis loss is minimized by
Ans= selecting good quality of magnetic material
Q.a transformer having 1000 primary turns, is connected to a 250V AC supply. For a
secondary voltage of 400V, the number of secondary turns should be
Ans= 1600
Q.the condition for maximum efficiency is
Ans= iron loss=copper loss
Q.the voltage regulation means
Ans= a) both A &C b) change in no load voltage to full load voltage upon no load voltage
c) change in full load voltage to no load voltage upon full load voltage d) change in no load
voltage to full load voltage upon full load voltage
Q. In a relation to transformer, 17:1 indicates that
Ans=For every 17 turns on primary, there is 1 turn on secondary
Q.The eddy current loss is given by
answer : Pe = Ke. Bm2. f2. t2 watt
Q. A transformer having 1250 primary turns, is connected to a 200V AC supply.
For a secondary voltage of 400V, the number of secondary turns should be?
answer: 2500
Q. In case of a transformer, the primary & secondary windings are wound on a
same limb, so as to reduce ?
answer: Leakage reactance
Q. The rating of transformer is given in terms of
Answer: Apparent power
Q. The equivalent resistance (R1e) referred to primary side is
answer: R1 + (R2 / k 2)
Q.At No load , following losses are negligible
answer: Copper loss
Q. The transformation ratio (k) means
Ans=a) I1/I2 b) N2/N1 c)V2/V1 d) all of these
Q. The copper saving in case of auto-transformer is
answer: k x weight of 2 winding transformer
Q. The voltage regulation is positive for ------ load.
Ans= a) capacitive b) inductive c) both a & c d) resistive
Q. The eddy current loss is minimized by
answer: Laminating the core
Q. A transformer having 2250 primary turns, is connected to a 1000V AC supply.
For a secondary voltage of 400V, the number of secondary turns should be
answer: 900
Q. The No Load primary current is the phasor sum of
a. Magnetizing component of No Load current b. Both A & B d. Loss
component of No Load current c. None of these
Q. The phenomenon of the self induction and mutual induction is felt, only when
the current in the coil is of ------ nature
Answer: AC
Q. In case of which of the following equipment, the EMF induced is due to static
induction?
answer: Transformer
Q. The equivalent resistance (R2e) referred to secondary side is
answer: R2 + (R1 . k 2)
Q. An emf induced in a coil due to change in current, in a neighbouring coil is
known as
answer: Mutually induced emf
Q. The voltage ratio means
answer: V1 / V2
Q. An emf induced in a coil due to change in current in the same coil is known as
answer: Self induced emf
Q. Before the point of maximum efficiency, ----- losses are more.
Ans=a) hysteresis loss & eddy current loss b) both a & b c) iron loss d)
copper loss
Q. The primary and secondary induced EMF's E1 and E2 in a two
winding transformer are always
answer: In phase with each other
Q. Sandwich windings are used for ----- type of transformer.
answer: Shell
Q. The voltage regulation is negative for ------ load
answer : Capacitive
Q. The equivalent leakage reactance (X1e) referred to primary side is
answer: X1 + (X2 / k 2)
Q. In case of a transformer, the No Load power loss means
answer: Iron loss
Q.Which of the following is /are the types of transformer ?
Ans= a) shell type b) core type c) berry type d) all of these
Q. A step up transformer increases
answer: Voltage
Q. Cylindrical windings are preferred for core type transformers as
Ans= a)easy for cooling b) easy for maintenance c) both A & B d) none of these
Q. ------- Losses are called as variable losses.
answer: Copper loss
Q. If the load current is halved, then copper losses will become
answer is: Quarter
Q. A step up transformer decreases
answer: Current
Q. The equivalent leakage reactance (X2e) referred to secondary side is
answer: X2 + (X1 . k 2)
Q. When will be the output of an AND gate is LOW ?
answer: When any input is LOW
Q. Cylindrical windings are used for ----- type of transformer.
answer: Core
Q. Iron losses vary with -----, while copper losses vary with ------.
answer: Voltage, current
Q. If the load current is halved, then core losses will become
answer: Remain same
Q. The losses obtained in Open Circuit Test are :
answer: Both A & B
Q. A step down transformer increases
answer: Current
Q. In case of phasor diagram of transformer, phasors for induced EMF's in
primary and secondary windings -------- flux.
answer is: Lags behind by 900 with
Q. The power factor is unity for purely ------ load
answer: Resistive
Q. ------- Losses are called as constant losses.
Ans=a) iron loss b) hysteresis loss + eddy current loss c) both A & B d) copper
loss
Q. The equivalent impedance (Z1e) referred to primary side is
answer: Z1 + (Z2 / k 2)
Q. According to Faraday's __________ Law, as long as there is change in flux,
induced emf persists.
answer : First
Q. In case of Core type of transformers, ---- surrounds ---- .
answer : Winding, core
Q. The condition for maximum efficiency is
Ans= a)both A & B b) iron loss=copper loss c) (hysteresis loss +eddy current
loss)= copper loss d) iron loss ⁢ hysteresis loss
Q. In case of Auto- transformer, which of the following is true , EXCEPT.
answer: Constant output voltage
Q. The primary and secondary windings of an ordinary transformer always have
answer: Common magnetic circuit
Q. The losses obtained in Short Circuit Test are .
answer: Eddy current losses
A step down transformer decreases
answer: Voltage
Q. In case of 2 winding transformer, the EMF / turn in primary winding is always -
--- the EMF / turn in secondary winding.
answer: Equal to
Q. Shell type of transformers use ---- windings.
answer: Sandwich
Q. In a relation to transformer, 15:1 indicates that
answer: For every 15 turns on primary, there is 1 turn on secondary
Q. Bushings are made with -----.
answer: Insulating materials
Q. In case of Shell type of transformers, ---- surrounds ---- .
answer: Core , winding
Q. After the point of maximum efficiency, ----- losses are more.
answer: Copper loss
Q. Core is made with -----.
answer: Magnetic materials
Q. Windings are made with -----.
answer: Conducting Materials
Q. The hysteresis loss is proportional to the following, EXCEPT
answer: Thickness
Q. As load changes, ----- losses change accordingly.
answer: Copper losses
Q. Which of the following is / are type of winding in transformer ?
Ans= a) both A & B b) sandwich c) cylindrical d) none of these
Q. Windings are made with -----.
Ans=a) iron b) aluminium c) both A & amp; B d) copper
Q. Which of the following relation is true for transformer?
Ans=a) V2 = E2 - I2Z2 b. E1 = V1 - I1Z1 c. E = 4.44 f Nm d. All of these
Q. A transformer having 250 primary turns, is connected to a 100V AC supply. For
a secondary voltage of 400V, the number of secondary turns should be
answer: 1000
Q. Which of the following relation is invalid for transformer?
answer: k = N2 / N1
Q. In case of Auto-transformer, which is of the following is true?
Ans= a. High efficiency as compared to 2 winding transformer b. Less weight as
compared to 2 winding transformer c. Single winding only d. All the above
Q. The copper loss is proportional to the following, EXCEPT
answer: Volume of magnetic material
Q. Core is made with -----.
Ans=a) copper b) cobalt c) iron d) both A & B
Q. The Open Circuit & Short Circuit Tests are carried out, so as to find.
Ans=a) efficiency b) regulation c) iron losses & amp; copper losses d) all of these
Q.an open delta connection carries the load of …… % of the delta-delta load
ans=57.7
Q.no-load speed of which of the following motor will be highest?
Ans= series motor
Q.the…… connection of transformer is used at the distribution end to step down
Ans= delta-star
Q.No-load speed of which of the following motor will be highest ?
Ans= series motor
Q.delta-delta connection of three phase transformer is used for …. Power and …..
voltage applications
Ans= low, low
Q.starters are used with DC motors because
Ans= to restrict armature current as there is no back emf while starting
Ans= to restrict armature current as there is no back emf while starting
Q.in DC shunt motors as load is reduced
Ans=the speed will remain almost/constant
Q.a DC series motor is that which
Ans= has its field winding consisting of thick wire and less turns
Q.For starting a DC motor a starter is required because
Ans=it limits the starting current to a safe value
Q.the type of DC motor used for shears and punches is
Ans= cumulative compound DC motor
Q.if a DC motor is connected across the AC supply it will
Ans= burn due to heat produced in the field winding by. Eddy currents
Q.to get the speed of DC motor below the normal without wastage of electrical
energy is used
Ans= ward leonard control
Q.when two DC series motors are connected in paralle, the resultant speed is
Ans= normal speed
Q.the speed of a DC shunt motor more than its full-load speed can be obtained
by
Ans= decreasing the field current
Q.in a DC shunt motor, speed is
Ans= independent of armature current
Q.when load power factor angle phase=30 degree, then the two transformers in
open delta at power factor of
Ans= 0.866,1
Q.the main transformer is tapped at…… % and teaser has the tapping at ….. %
Ans=86.6,50
Q.the direction of rotation of a DC series of a DC series motor can be changed by
Ans= interchanging field terminals
Q.when load power factor angle phase=30 degree, then the two transformer in
open delta operate at power factor of
Ans= 0.5,0.707
Q. the direction of rotation of a DC series motor can be changed by
Q.a direct on line starter is used : for starting motors
Ans= up to 5 H.P
Q.what will happen if the back emf of a DC motor vanishes suddenly?
Ans= the armature may burn
Q.in case of DC shunt motors the speed is dependent on back emf only because
Ans= flux is practically constant in DC shunt motors
Q.in a Dc shunt motor, under the conditions of maximum power, the current in
the armature will be
Ans= more than full-load current
Q.these days DC motors are widely used in
Ans=electric traction
Q.by looking at which part of the motor, it can be easily confirmed that a
particular motor is DC motor
Ans= commutator
Q.in delta-star transformer , the ratio of secondary to primary voltage is…. Times
the transformation ratio of each transformer
Ans= 1.732 times
Q.an open delta connection carries the load of …. % of the remaining capacity of
two transformer
Ans= 57.7
Q.which of the following application requires high starting torque?
Ans= locomotive
Q.in the Y-Y connection of three phase transformer the phase shift between the
line voltage and the phase voltage is….. on both primary and secondary
Ans= 30 degree
Q.if a DC motor is to be selected for conveyors, which motor would be preferred?
Ans= series motor
Q.in the delta-delta connection, the phase voltage is….. the line voltage
Ans= k
Q. in the delta-star connection of three phase transformer, the angular
displacement between primary and the secondary voltage is
Ans= 30 degree
Q.which DC motor will be preferred for machine tools?
Ans=shunt motor
Q.the neutral shifting of transformer result in
Ans= a) unequal voltage , unequal current b) insulation stressing and breakdown
c) both a and b
Q.differentially compound DC motors can find applications requiring
Ans= low starting torque
Q.the direction of rotation of a dc series motor can be reversed
Ans= by interchanging the field terminals
Q,the main transformer is tapped at ……% and teaser has tapping at…..%
Ans= 86.6,50
Q.according to flemming’s left hand rule, when the forefinger points in the
direction of the field or flux, the middle finger will point in the direction of
Ans= current in the conductor
Q.delta-delta connection of three phase transformer is used for high voltage
application because
Ans= a) phase voltage is equal to line voltage b) emf/ turns more c) turns/ phase
are more d) insulation required is more e) all of these
Ans=to restric armature current as there is no back emf while starting
Q.A D.C. series motor is that which
answer: has its field winding consisting of thick wire and less turns
Q.A direct on line starter is used: for starting motors
answer: up to 5 H.P.
Q.A three point starter is considered suitable for
answer: shunt as well as compound motors
Q.According to Fleming's left-hand rule, when the forefinger points in the
direction of the field or flux, the middle finger will point in the direction of
answer is: current in the conductor aovtaat of conductor
Q.As -the load is increased the speed of D.C. shunt motor will
answer is: reduce slightly
Q.As there is no back e.m.f. at the instant of starting a D.C. motor, in order to
prevent a heavy current from flowing though the armature circuit
answer is: a resistance is connected in series with armature
Q.At the instant of starting when a D.C. motor is put on supply, it behaves like
answer is: a low resistance circuit
Q.Buses, trains, trolleys, hoists, cranes require high starting torque and therefore
make use of
answer is: D.C. series motor
Q.By looking at which part of the motor, it can be easily confirmed that a
particular motor is D.C. motor?
answer is: Commutator
Q.D.C. generators are installed near the load centres to reduce
answer is: line losses
Q.D.C. generators are normally designed for maximum efficiency around
answer is: full-load
Q.D.C. series motors are used
answer is: in none of the above situations.
Q.D.C. shunt motors are used for driving
answer is: machine tools
Q.Differentially compound D.C. motors can find applications requiring
answer is: low starting torque
Q.Following motor is used where high starting torque and wide speed range
control is required.
answer is: D.C. motor
Q.For a D.C. shunt motor if the excitation is changed
answer is: torque will change but power will remain constant
Q.For constant torque drive which speed control method is preferred ?
answer is: Armature voltage control
Q.For starting a D.C. motor a starter is required because
answer is: it limits the starting current to a safe value
Q.For the same H.P. rating and full load speed, following motor has poor starting
torque
answer is: differentially compounded
Q.For which of the following applications a D.C. motor is preferred over an A.C.
motor ?
answer is: Variable speed operation
Q.Hopkinson's test on D.C. machines is conducted at
answer is: full-load
Q.Select one:
answer is: is to be derated by a factor recommended by manufacturer and select
the next higher H.P. motor
Q.If a D.C. motor is connected across the A.C. supply it will
answer is: burn due to heat produced in the field winding by .eddy currents
Q.If a D.C. motor is to be selected for conveyors, which rriotor would be preferred
?
answer is: Series motor
Q.If a D.C. shunt motor is working at no load and if shunt field circuit suddenly
opens
answer is: this will result in excessive speed, possibly destroying armature due to
excessive centrifugal stresses D. motor will run at very slow speed
Q.If I2 be the armature current, then speed of a D.C. shunt motor is
answer is: independent of Ia
Q.If the field of a D.C. shunt motor gets opened while motor is running
answer is: the motor will attain dangerously high speed 1
Q.If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will
answer is: increase
Q.If the supply voltage for a D.C. motor is increased, which of the following will
decrease ?
answer is: Full-load current
Q.If the terminals of armature of D.C. motor are interchanged, this action will
offer following kind of braking
answer is: plugging
Q.In a D.C. generator, the iron losses mainly take place in
answer is: armature rotor
Q.In a D.C. shunt motor, under the conditions of maximum power, the current in
the armature will be
answer is: more than full-load current
Q.In a manual shunt motor starter
answer is: over load relay is connected in series and no volt relay in parallel with
the load
Q.In case of conductively compensated D.C. series motors, the compensating
winding is provided
answer is: in series with armature winding
Q.In case of D.C. shunt motors the speed is dependent on back e.m.f. only
because
answer is: flux is practically constant in D:C. shunt motors
Q.In case-the conditions for maximum power for a D.C. motor are established,
the efficiency of the motor will be
answer is: less than 50%
Q.In D.C. shunt motors as load is reduced
answer is: the speed will remain almost/constant
Q.In D.C. machines fractional pitch winding is used
answer is: to reduce the sparking
Q.In D.C. motor which of the following can sustain the maximum temperature
rise?
Select one:
answer is: Field winding
Q.In Ward-Leonard control the lower limit of speed is imposed by
answer is: residual magnetism of the generator
Q.No-load speed of which of the following motor will be highest ?
Q.Regenerative method of braking is based on that
answer is: back e.m.f. is equal to the applied voltage
Q.Sparking at the commutator of a D.C. motor may result in
answer is: all of the above
Q.Speed control by Ward Leonard method gives uniform speed variation
answer is: in both directions
Q.Starters are used with D.C. motors because
answer is: to restrict armature current as there is no back e.m.f. while starting
Q.The armature torque of the D.C. shunt motor is proportional to
answer is: armature current only
Q.The armature voltage control of D.C. motor provides
answer is: constant torque drive
Q.The condition for maximum efficiency for a D.C. generator is
answer is: variable losses = constant losses
Q.The current drawn by the armature of D.C. motor is directly proportional to
answer is: the torque required
Q.The losses occurring in a D.C. generator are given below. Which loss is likely to
have highest proportion at rated load of the generator ?
answer is: armature copper loss
Q.The main disadvantage of the Ward-Leonard control method is
answer is: all of the above
Q.The mechanical power developed by a shunt motor will be maximum when the
ratio of back e.m.f. to applied voltage is
answer is: 0.5
Q.The plugging gives the
answer is: highest torque braking
Q.The speed of a D.C. series motor is
answer is: inversely proportional to the armature current
Q.The speed of a D.C. shunt motor can be increased by
answer is: increasing the resistance in field circuit
Q.The starting resistance of a D.C. motor is generally
answer is: low
Q.The total losses in a well designed D.C. generator of 10 kW will be nearly
answer is: 500 W
Q.The type of D.C. motor used for shears and punches is
answer is: cumulative compound D.C. motor
Q.These days D.C. motors are widely used in
answer is: electric traction
Q.Three point starter can be used for
answer is: both shunt and compound motor
Q.Torque developed by a D.C. motor depends upon
answer is: all above factors
Q.Usually wide and sensitive speed control is desired in case of
answer is: colliery winders
Q.Ward-Leonard control is basically a
answer is: voltage control method
Q.What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
answer is: The armature may burn
Q.When two D.C. series motors are connected in parallel, the resultant speed is
answer is: normal speed
Q.Which D.C. motor is preferred for elevators ?
answer is: Cumulative compound motor
Q.Which motor has the poorest speed control?
Q.Which motor should not be started on no-load ?
Q.Which of the following application requires high starting torque ?
answer is: Locomotive
Q.Which of the following law/rule can he used to determine the direction of
rotation of D.C. motor ?
answer is: Fleming's left-hand rule
Q.Which of the following loss in a D.C. generator varies significantly with the load
current ?
answer is: Armature copper loss
Q.Which of the following losses are significantly reduced by laminating the core
of a D.C. generator ?
answer is: Eddy current losses
Q.Which of the following motor has the poorest speed regulation ?
Q.Which of the following motors is most suitable for signalling devices and many
kinds of timers ?
answer is: Reluctance motor
Q.Which of the following motors is usually used in house-hold refrigerators ?
answer is: Single phase induction motor (split phase start or induction run motor)
Q.Which of the following tests will be suitable for testing two similar D.C. series
motors of large capacity ?
answer is: Field test
Q.Which one of the following is not necessarily the advantage of D.C. motors over
A.C. motors ?
answer is: Low cost
Q.Why are the D.C. motors preferred for traction applications ?
answer is: The speed is inversely proportional to the torque and the torque is
proportional to square of armature current
Q.A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor
e.m.f. will be
answer is: 2 Hz
Q.A 3-phase induction motor stator delta connected, is carrying full load and one
of its fuses blows out. Then the motor
answer is: will continue running burning its one phase
Q.A 3-phase slip ring motor has
answer is: wound rotor
Q.A 500 kW, 3-phase, 440 volts, 50 Hz, A.C. induction motor has a speed of 960
r.p.m. on full load. The machine has 6 poles. The slip of the machine will be
answer is: 0.04
Q.A change of 4% of supply voltage to an induction motor will produce a change
of appromimately
answer is: 16% in the rotor torque
Q.A double squirrel-cage induction motor has
answer is: two parallel windings in rotor
Q.A squirrel cage induction motor is not selected when
answer is: higher starting torque is the main consideration
Q.An induction motor can run at synchronous speed when
answer is: e.m.f. is injected in the rotor circuit
Q.An induction motor is
answer is: self-starting with low torque
Q.An induction motor is identical to
answer is: asynchronous motor
Q.An induction motor with 1000 r.p.m. speed will have
answer is: 6 poles
Q.As load on an induction motor goes on increasing
answer is: its power factor goes on increasing up to full load and then it falls again
Q.considered
Select one:
answer is: in parallel
Q.following machines
Select one:
answer is: D.C. shunt motor
Q.For driving high inertia loods best type of induction motor suggested is
answer is: slip ring type
Q.For which motor the speed can be controlled from rotor side ?
answer is: Slip-ring induction motor
Q.If a 3-phase supply is given to the stator and rotor is short circuited rotor will
move
answer is: in the same direction as the direction of the field
Q.If an induction motor with certain ratio of rotor to stator slots, runs at 1/7 of
the normal speed, the phenomenon will be termed as
answer is: crawling
Q.If any two phases for an induction motor are interchanged
answer is: the motor will run in reverse direction
Q.In a squirrel cage motor the induced e.m.f. is
answer is: slip times the stand still e.m.f. induced in the rotor
Q.In a star-delta starter of an induction motor
answer is: applied voltage perl stator phase is 57.7% of the line voltage
Q.In a three-phase induction motor
answer is: iron losses in stator will be more than that in rotor
Q.In a three-phase induction motor
answer is: power factor at starting is low as compared to that while running
Q.In a three-phase induction motor, the number of poles in the rotor winding is
always
answer is: equal to number of poles in stator
Q.In an induction motor if air-gap is increased
answer is: the power factor will be low
Q.In an induction motor the relationship between stator slots and rotor slots is
that
answer is: stator slots are not exact multiple of rotor slots
Q.In an induction motor, no-load the slip is generally
answer is: less than 1%
Q.In case of a double cage induction motor, the inner cage has
answer is: high inductance arid low resistance
Q.In case of the induction motors the torque is
answer is: directly proportional to slip
Q.In case the air gap in an induction motor is increased
answer is: the power factor will decrease
Q.In induction motor, percentage slip depends on
answer is: copper losses in motor
Q.In medium sized induction motors, the slip is generally around
answer is: 4%
Q.In Ns is the synchronous speed and s the slip, then actual running speed of an
induction motor will be
answer is: (l-s)Ns
Q.In squirrel cage induction motors, the rotor slots are usually given slight skew
in order to
answer is: reduce magnetic hum
Q.In the squirrel-cage induction motor the rotor slots are usually given slight skew
answer is: to reduce the magnetic hum and locking tendency of the rotor
Q.In three-phase induction motors sometimes copper bars are placed deep in
the rotor to
answer is: improve starting torque
Q.In three-phase squirrel-cage induction motors
answer is: rotor conductors are short-circuited through end rings
Q.It is advisable to avoid line starting of induction motor and use starter because
answer is: motor takes five to seven times its full load currentIt is advisable to
Q.avoid line-starting of induction motor and use starter because
answer is: motor takes five to seven times its full load current
Q.Less maintenance troubles are experienced in case of
answer is: squirrel cage induction motor
Q.Low voltage at motor terminals is due to
answer is: any one of the above
Q.Lubricant used for ball bearing is usually
answer is: grease
Q.motor
Select one:
answer is: will stop and carry heavy current causing permanent damage to its
winding
Q.Short-circuit test on an induction motor cannot be used to determine
answer is: windage losses
Q.Size of a high speed motor as compared to low speed motor for the same H.P.
will be
answer is: smalle
Q.Slip ring motor is preferred over squirrel cage induction motor where
answer is: high starting torque is required
Q.Slip ring motor is recommended where
answer is: all above features are required
Q.Slip rings are usually made of
answer is: phospor bronze
Q.Star-delta starting of motors is not possible in case of
answer is: single phase motors
Q.Stepless speed control of induction motor is possible by which of the following
methods ?
answer is: Changing the number of poles
Q.Temperature of the stator winding of a three phase induction motor is
obtained by
answer is: all above methods
Q.The torque developed in the cage induction motor with autostarter is
answer is: K2 x torque with direct switching
Q.The complete circle diagram of induetion motor can be drawn with the help of
data found from
a.blocked rotor test b. noload test c. stator resistance test d. all of the above
Q.The efficiency of an induction motor can be expected to be nearly
answer is: 80 to 90%
Q.The frame of an induction motor is usually made of
answer is: cast iron
Q.The frame of an induction motor is usually made of
answer is: cast iron
Q.The good power factor of an induction motor can be achieved if the average
flux density in the air gap is
answer is: small
Q.The injected e.m.f. in the rotor of induction motor must have
answer is: the same frequency as the slip frequency
Q.The low power factor of induction motor is due to
a.rotor leakage reactance b. all of the above c. stator reactance d. the reactive
lagging magnetizing current necessary to generate the magnetic flux
Q.The maximum torque in an induction motor depends on
a.frequency b. all of the above c. square of supply voltage d. rotor inductive
reactanc
Q.The number of slip rings on a squirrel cage induction motor is usually
a. four
b. three
c. none
d. two
Q.The power factor of an induction motor under no-load conditions will be closer
to
answer is: 0.2 lagging
Q.The power scale of circle diagram of an induction motor can be found from
answer is: short-circuit test only
Q.The purpose of using short-circuit gear is
answer is: to short circuit the rotor at slip rings
Q.The rotor of an induction motor runs at
answer is: below synchronous speed
Q.The shaft of an induction motor is made of
answer is: stiff
Q.The shaft of an induction motor is made of
answer is: carbon steel
Q.The shape of the torque/slip curve of induction motor is
answer is: rectangular parabola
Q.The speed of a squirrel-cage induction motor can be controlled by all of the
following except
answer is: changing winding resistance
Q.The starting torque of a 3-phase squirrel cage induction motor is
answer is: 1.5 times the full load torque
Q.The starting torque of a squirrel-cage induction motor is
answer is: low
Q.The starting torque of a three phase induction motor can be increased by
a. increasing slip b. increasing current
answer is: both A. and B.
Q.The stating torque of the slip ring induction motor can be increased by adding
answer is: external resistance to the rotor
Q.The term 'cogging' is associated with
answer is: induction motors
Q.The torque developed by a 3-phase induction motor least depends on
answer is: shaft diameter
Q.The torque of a rotor in an induction motor under running condition is
maximum
answer is: at the value of the slip which makes rotor reactance per phase equal to
the resistance per phase
Q.The torque of an induction motor is
answer is: directly proportional to slip
Q.The vafcie of transformation ratio of an induction motor can be found by
answer is: short-circuit test only
Q.What will happen if the relative speed between the rotating flux of stator and
rotor of the induction motor is zero ?
answer is: The rotor will not run
Q.Which is of the following data is required to draw the circle diagram for an
induction motor ?
answer is: Block rotor test, no-load test and stator resistance test
Q.Which motor is preferred for use in mines where explosive gases exist ?
answer is: Air motor
Q.Which of the following component is usually fabricated out of silicon steel ?
answer is: Statorcore
Q.Which of the following methods is easily applicable to control the speed of the
squirrel-cage induction motor ?
answer is: By changing the number of stator poles
Q.Which type of bearing is provided in small induction motors to support the rotor
shaft ?
answer is: Ball bearings
Q.As load on an induction motor goes on increasing
answer is: its power factor goes on increasing up to full load and then it falls again
Q.Blocked rotor test on induction motors is used to find out
a. all of the above b. short-circuit current under rated voltage c. power factor on
short circuit d. leakage reactance
Q.DOL starting of induction motors is usually restricted to
answer is: low horsepower motors
Q.For driving high inertia loods best type of induction motor suggested is
answer is: slip ring type
Q.For which motor the speed can be controlled from rotor side
answer is: Slip-ring induction motor
Q.If a 3-phase supply is given to the stator and rotor is short circuited rotor will
move
answer is: in the same direction as the direction of the field
Q.In a star-delta starter of an induction motor
answer is: applied voltage perl stator phase is 57.7% of the line voltage
Q.In an induction motor if air-gap is increased
answer is: the power factor will be low
Q.In induction motor, percentage slip depends on
answer is: copper losses in motorIn the circle diagram for induction motor, the
Q.diameter of the circle represents Select one:
answer is: rotor current
Q.In three-phase squirrel-cage induction motors
answer is: rotor conductors are short-circuited through end rings
Q.Insertion of resistance in the rotcir of an induction motor to develop a given
torque
answer is: rotor current rernains same
Q.It is advisable to avoid line starting of induction motor and use starter because
answer is: motor takes five to seven times its full load current
Q.Reduced voltage starter can be used with
answer is: squirrel cage as well as slip ring induction motor
Q.Rotor rheostat control method of speed control is used for
answer is: slip ring induction motors only
Q.Short-circuit test on an induction motor cannot be used to determine
answer is: windage losses
Q.Star-delta starting of motors is not possible in case of
answer is: single phase motors
Q.Stepless speed control of induction motor is possible by which of the following
methods ?
answer is: Changing the number of poles
Q.Temperature of the stator winding of a three phase induction motor is obtained
by
a. embedded temperature method b. all above methods c. resistance rise
method d. thermometer method
Q.The 'cogging' of an induction motor can be avoided by
answer is: having number of rotor slots more or less than the number of stator
slots (not equal)
Q.The 'crawling" in an induction motor is caused by
answer is: harmonics developed in the motor
Q.The auto-starters (using three auto transformers) can be used to start cage
induction motor of the following type
Ans= a. star connected only b. delta connected only c. A. and B. both
Q.The circle diagram for an induction motor cannot be used to determine
answer is: efficiency
Q.The complete circle diagram of induetion motor can be drawn with the help of
data found from
a. blocked rotor test b. noload test c. stator resistance test d. all of the above
Q.The low power factor of induction motor is due to
a. stator reactance b. all of the above c. the reactive lagging magnetizing current
necessary to generate the magnetic flux d. rotor leakage reactance
Q.The number of slip rings on a squirrel cage induction motor is usually
a. none b. three c. four d. two
Q.What will happen if the relative speed between the rotating flux of stator and
rotor of the induction motor is zero ?
answer is: The rotor will not run
Q.When R2 is the rotor resistance, X2 the rotor reactance at supply frequency and
s the slip, then the condition for maximum torque under running conditions will be
answer is: R2 = sX2
Q.Which is of the following data is required to draw the circle diagram for an
induction motor ?
answer is: Block rotor test, no-load test and stator resistance test
Q. An open delta connection carries the load of ……..%l of the
delta -delta load
Ans=57.7
Q. no-load speed of which of the following motor will be
highest ?
Ans=series motor
Q. the …….. connection of transformers is used at the
distribution end to step down the voltage.
Ans=delta-star
Q. delta-delta connection of three phase transformer is used
for…… power and ……. Voltage applications
Ans=low,low
Q. starters are used with d.c motors because
Ans=to restrict armature current as there is no back emf while
starting
Q. in dc shunt motors as load is reduced
Ans= the speed will remain almost/constant
Q. a dc series motor is that which
Ans= has its field winding consisting of thick wire and less turns
Q. for starting a dc motor a starter is required because
Ans= it limits the starting current to a safe value
Q.the type of dc motor used for shears and punches is
Ans=cumulative compound dc motor
Q. if a dc motor is connected across the ac supply It will
Ans=burn due to heat produced in the field winding by eddy
currents
Q. to get the speed of dc motor below the normal without
wastage of electrical energy is used
Ans=ward Leonard control
Q. when two dc series motors are connected in parallel, the
resultant speed is
Ans= normal speed
Q. the speed of a dc shunt motor more than its full-load speed
can be obtained by
Ans= decreasing the field current
Q. in a dc shunt motor speed is
Ans= independent of armature current
Q. when load power factor angle phi=30 degree, then the two
transformers In open delta operate at power factor of
Ans=0.866,1
Q.the main transformer is tapped at…… % and teaser has the
tapping at …..%
Ans= 86.6,50
Q.the direction of rotation of a dc series motor can be changed
by
Q. when load power factor angle phi=30 degree, then the two
transformers in open delta operate at power factor of
Ans=0.5,0.707
Q.a direct on line starter is used for starting motors
Ans= up to 5 H.P
Q.what will happen if the back emf of a dc motor vanishes
suddenly?
Ans= the armature may burn
Q.in case of dc shunt motors the speed is dependent on back
emf only because
Ans= flux is practically constant in dc shunt motors
Q.in a dc shunt motor, under the conditions of maximum
power, the current in the armature will be
Ans= more than full-load current
Q.these days dc motors are widely used in
Ans= electric traction
Q.by looking at which part of the motor, it can be easily
confirmed that a particular motor is dc motor?
Ans= commutator
Q.in delta-transformer the ratio of secondary to primary
voltage is….. times the transformation ratio of each
transformer
Ans=1.732 time
Q.an open delta connection carries the load of….. % of the
remaining capacity of two transformer
Ans=57.7
Q.which of the following application requires high starting
torque?
Ans=locomotive
Q. in the Y-Y connection of three phase transformer the phase
shift between the line voltage and the phase voltage is……. On
both primary and secondary
Ans=30 degree
Q.if a dc motor is to be selected for conveyors, which motor
would be preferred?
Ans= series motor
Q.in the delta-delta connection the phase voltage is…… the
line voltage
Ans=k
Q.in the delta – star connection of three phase transformer
the angular displacement between primary and the secondary
voltage is
Ans= 30 degree
Q.which dc motor will be preferred for machine tools?
Ans= shunt motor
Q.the neutral shifting of transformer results in
Ans= A] unequal voltage , unequal current
B] insulation stressing and breakdown
C] both a and b
Q. differentially compound dc motors can find application
requiring
Ans=low starting torque
Q.the direction of rotation of dc series motor can be reversed
Ans= by interchanging the field terminals
Q.according to Flemings left hand rule, when the forefinger
points in the direction of the field or flux the middle finger will
point in the direction of
Ans= current in the conductor aovtaat of conductor
Q.delta-delta connection of three phase transformer is used
for high voltage application be caused
Ans= a] phase voltage is equal to line voltage b] emf / turn is
more c] turns/ phase are more d] insulation required is more
e] all of the above
Q.starter are used with dc motors because
Ans= to restrict armature current as there is no back emf while
starting
Q.no-load speed of which of the following motor will be
highest?
Ans= series motor
Q.
Question 1
1. Laminations of core are generally made of
Select one:
a. carbon.
b. castiron.
c. stainless steel.
d. silicon steel.
Feedback
The correct answer is: stainless steel.
Question 2
10. In D.C. generators, the cause of rapid brush wear may be
Select one:
a. any of the above
b. severe sparking
c. rough commutator surface
d. imperfect contact
Feedback
The correct answer is: any of the above
Question 3
11. In lap winding, the number of brushes is always.
Select one:
a. two
b. half the number of poles
c. double the number of poles

d. same as the number of poles
Feedback
The correct answer is: same as the number of poles
Question 4
12. For a D.C. generator when the number of poles and the number of armature
conductors is fixed, then which winding will give the higher e.m.f. ?
Select one:
a. Either of (a) and (b) above
b. Depends on other features of design
c. Lap winding
d. Wave winding
Feedback
The correct answer is: Wave winding
Question 5
13. Iron losses in a D.C. machine are independent of variations in
Select one:
a. load
b. speed
c. speed and voltage
d. voltage
Feedback
The correct answer is: load
Question 6
14. In D.C. generators, current to the external circuit from armature is given through
Select one:
a. none of above
b. solid connection
c. slip rings
d. commutator
Feedback
The correct answer is: commutator
Question 7
15. Brushes of D.C. machines are made of
Select one:
a. carbon
b. hard copper
c. all of above
d. soft copper
Feedback
The correct answer is: carbon
Question 8
16. If B is the flux density, I the length of conductor and v the velocity of conductor, then
induced e.m.f. is given by
Select one:
a. Bl2v
b. Blv
c. Blv2
d. Bl2v2
Feedback
The correct answer is: Blv
Question 9
17. The material for commutator brushes is generally
Select one:
a. carbon
b. mica
c. cast iron
d. copper
Feedback
The correct answer is: carbon
Question 10
18. The insulating material used between the commutator segments is normally
Select one:
a. mica
b. graphite
c. insulating varnish
d. paper
Feedback
The correct answer is: mica
Question 11
19. Eddy currents are induced in the pole shoes of a D.C. machine due to
Select one:
a. all above
b. oscillating magnetic field
c. pulsating magnetic flux
d. relative rotation between field and armature
Feedback
The correct answer is: relative rotation between field and armature
Question 12
2. The armature of D.C. generator is laminated to
Select one:
a. insulate the core
b. provide the bulk

c. reduce the bulk
d. reduce eddy current loss
Feedback
The correct answer is: reduce eddy current loss
Question 13
20. In case of D.C. machine winding, number of commutator segments is equal to
Select one:
a. number of armature turns
b. number of armature conductors
c. number of armature coil sides

d. number of armature coils
Feedback
The correct answer is: number of armature coils
Question 14
21. The function of pole shoes in the case of D.C. machine is?
Select one:
a. to discharge all the above functions.
b. to reduce the reluctance of the magnetic path.

c. to support the field coil.
d. to spread out the flux to achieve uniform flux density
Feedback
The correct answer is: to discharge all the above functions.
Question 15
22. The demagnetising component of armature reaction in a D.C. generator
Select one:
a. reduces generator e.m.f.
b. reduces interpoles flux density
c. increases armature speed

d. results in sparking trouble
Feedback
The correct answer is: reduces generator e.m.f.
Question 16
23. Magnetic field in a D.C. generator is produced by:
Select one:
a. electromagnets
b. both (a) and (b)

c. none of the above
d. permanent magnets
Feedback
The correct answer is: none of the above
Question 17
24.The e.m.f. generated by a shunt wound D.C. generator isE. Now while pole flux
remains constant, if the speed of the generator is doubled, the e.m.f. generated will be
Select one:
a. E
b. slightly less than E
c. E/2
d. 2E
Feedback
The correct answer is: 2E
Question 18
25. Satisfactory commutation of D.C. machines requires
Select one:
a. all of the above
b. brushes should smoothly run in the holders
c. smooth, concentric commutator properly undercut

d. brushes should be of proper grade and size
Feedback
The correct answer is: all of the above
Question 19
3. The resistance of armature winding depends on
Select one:
a. number of conductors
b. all of the above

c. length of conductor
d. cross-sectional area of the conductor
Feedback
Question 20
4. The field coils of D.C. generator are usually made of
Select one:
a. cast iron
b. mica
c. carbon
d. copper
Feedback
The correct answer is: copper
Question 21
5. The commutator segments are connected to the armature conductors by means of
Select one:
a. insulation pads
b. resistance wires
c. copper lugs
d. brazing
Feedback
The correct answer is: copper lugs
Question 22
6. In a commutator
Select one:
a. mica is harder than copper
b. none of the above
c. copper is harder than mica

d. mica and copper are equally hard
Feedback
The correct answer is: mica is harder than copper
Question 23
7. In D.C. generators the pole shoes are fastened to the pole core by.
Select one:
a. counter sunk screws
b. brazing
c. welding
d. rivets
Feedback
The correct answer is: counter sunk screws
Question 24
of.
Select one:
a. either of the above
c. lines of force
d. motion of conductor
Feedback
The correct answer is: lines of force
Question 25
thumb points towards.
Select one:
a. direction of motion of conductor, if forefinger points along the lines of flux
b. direction of motion of the conductor if forefinger points in the direction of generated
e.m.f.
c. direction of flux
d. direction of induced e.m.f.
Feedback
The correct answer is: direction of motion of conductor, if forefinger points along the
lines of flux
Question 1
A D.C. series motor is that which
Select one:
a. has its field winding consisting of thick wire and less turns
b. has almost constant speed
c. can be started easily without load

d. has a poor torque
Feedback
The correct answer is: has its field winding consisting of thick wire and less turns
Question 2
A direct on line starter is used: for starting motors
Select one:
a. up to 20 H.P.
b. up to 10 H.P.
c. up to 15 H.P.
d. up to 5 H.P.
Feedback
The correct answer is: up to 5 H.P.
Question 3
A three point starter is considered suitable for
Select one:
a. shunt motors
b. all D.C. motors
c. shunt as well as compound motors

d. shunt, compound and series motors
Feedback
The correct answer is: shunt as well as compound motors
Question 4
According to Fleming's left-hand rule, when the forefinger points in the direction of the
field or flux, the middle finger will point in the direction of
Select one:
a. none of the above
b. resultant force on conductor

c. current in the conductor aovtaat of conductor
Feedback
The correct answer is: current in the conductor aovtaat of conductor
Question 5As -the load is increased the speed of D.C. shunt motor will
Select one:
a. reduce slightly
b. increase proportionately
c. remains unchanged
d. increase slightly
Feedback
The correct answer is: reduce slightly
Question 6
As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a
heavy current from flowing though the armature circuit
Select one:
a. a high value resistor is connected across the field winding
b. a resistance is connected in series with armature

c. a resistance is connected parallel to the armature
d. armature is temporarily open circuited
Feedback
The correct answer is: a resistance is connected in series with armature
Question 7
At the instant of starting when a D.C. motor is put on supply, it behaves like
Select one:
a. a low resistance circuit
c. a capacitive circuit
d. a highly resistive circuit
Feedback
The correct answer is: a low resistance circuit
Question 8
Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make
use of
Select one:
a. all of above motors
b. induction motor
c. D.C. shunt motor

d. D.C. series motor
Feedback
The correct answer is: D.C. series motor
Question 9
By looking at which part of the motor, it can be easily confirmed that a particular motor
is D.C. motor?
Select one:
a. Frame
b. Commutator
c. Shaft
d. Stator
Feedback
The correct answer is: Commutator
Question 10
D.C. generators are installed near the load centres to reduce
Select one:
a. corona losses
b. sparking
c. line losses
d. iron losses
Feedback
The correct answer is: line losses
Question 11
D.C. generators are normally designed for maximum efficiency around
Select one:
a. rated voltage
b. full-load
c. rated r.p.m.
d. all of the above
Feedback
The correct answer is: full-load
Question 12
D.C. series motors are used
Select one:
a. where load changes frequently
b. in none of the above situations.
c. where load is constant
d. where constant operating speed is needed
Feedback
The correct answer is: in none of the above situations.
Question 13
D.C. shunt motors are used for driving
Select one:
a. trains
b. cranes
c. machine tools
d. hoists
Feedback
The correct answer is: machine tools
Question 14
Differentially compound D.C. motors can find applications requiring
Select one:
a. high starting torque
b. low starting torque
c. variable speed
d. frequent on-off cycles
Feedback
The correct answer is: low starting torque
Question 15
Following motor is used where high starting torque and wide speed range control is
required.
Select one:
a. Single phase capacitor start
b. Induction motor
c. D.C. motor
d. Synchronous motor
Feedback
The correct answer is: D.C. motor
Question 16
For a D.C. shunt motor if the excitation is changed
Select one:
a. torque, power and speed, all will change
b. torque will remain constant
c. torque and power both will change

d. torque will change but power will remain constant
Feedback
The correct answer is: torque will change but power will remain constant
Question 17
For constant torque drive which speed control method is preferred ?
Select one:
a. Armature voltage control
b. Field control
c. Mechanical loading system

d. Shunt armature control
Feedback
The correct answer is: Armature voltage control
Question 18
For starting a D.C. motor a starter is required because
Select one:
b. it limits the starting current to a safe value
c. it starts the motor

d. it limits the speed of the motor
Feedback
The correct answer is: it limits the starting current to a safe value
Question 19
For the same H.P. rating and full load speed, following motor has poor starting torque
Select one:
a. series
b. shunt
c. cumulativelyc'ompounded
d. differentially compounded
Feedback
The correct answer is: differentially compounded
Question 20
For which of the following applications a D.C. motor is preferred over an A.C. motor ?
Select one:
a. Low speed operation
b. Fixed speed operation
c. Variable speed operation
d. High speed operation
Feedback
The correct answer is: Variable speed operation
Question 21
Hopkinson's test on D.C. machines is conducted at
Select one:
a. overload
b. no-load
c. full-load
d. part load
Feedback
The correct answer is: full-load
Question 22
Select one:
a. is to be derated by a factor recommended by manufacturer and select the next
higher H.P. motor
b. of lower H.P. should be selected

c. of higher H.P. should be selected
Feedback
The correct answer is: is to be derated by a factor recommended by manufacturer and
select the next higher H.P. motor
Question 23
If a D.C. motor is connected across the A.C. supply it will
Select one:
a. burn due to heat produced in the field winding by .eddy currents
b. not run
c. run at lower speed

d. run at normal speed
Feedback
The correct answer is: burn due to heat produced in the field winding by .eddy currents
Question 24
If a D.C. motor is to be selected for conveyors, which rriotor would be preferred ?
Select one:
a. Cumulative compound motor
b. Differentially compound motor

c. Shunt motor
d. Series motor
Feedback
The correct answer is: Series motor
Question 25
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens
Select one:
a. nothing will happen to the motor
b. this will make armature to take heavy current, possibly burning it

c. this will result in excessive speed, possibly destroying armature due to excessive
centrifugal stresses D. motor will run at very slow speed
Feedback
The correct answer is: this will result in excessive speed, possibly destroying armature
due to excessive centrifugal stresses D. motor will run at very slow speed
Question 26
If I2 be the armature current, then speed of a D.C. shunt motor is
Select one:
a. varies as la
b. independent of Ia
c. varies as (Ia)
d. proportional to la
Feedback
The correct answer is: independent of Ia
Question 27
If the field of a D.C. shunt motor gets opened while motor is running
Select one:
a. the motor will attain dangerously high speed 1
b. the speed of motor will be reduced %
c. the armature current will reduce

d. the motor will continue to nuvat constant speed
Feedback
The correct answer is: the motor will attain dangerously high speed 1
Question 28
If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will
Select one:
a. increase
b. become zero
c. decrease
d. remain same
Feedback
The correct answer is: increase
Question 29
If the supply voltage for a D.C. motor is increased, which of the following will decrease ?
Select one:
a. Operating speed
b. All of the above

c. Starting torque
d. Full-load current
Feedback
The correct answer is: Full-load current
Question 30
If the terminals of armature of D.C. motor are interchanged, this action will offer
following kind of braking
Select one:
a. dynamic braking

c. regenerative
d. plugging
Feedback
The correct answer is: plugging
Question 31
In a D.C. generator, the iron losses mainly take place in
Select one:
a. commutator
b. armature conductors
c. yoke
d. armature rotor
Feedback
The correct answer is: armature rotor
Question 32
In a D.C. shunt motor, under the conditions of maximum power, the current in the
armature will be
Select one:
a. rated full-load current
b. more than full-load current
c. less than full-load current

d. almost negligible
Feedback
The correct answer is: more than full-load current
Question 33
In a manual shunt motor starter
Select one:
a. over load relay and no volt relay are both connected in parallel with the load
b. over load relay is connected in series and no volt relay in parallel with the load
c. over load relay is connected in parallel and no volt relay in series with the load
d. over load relay and no volt relay are both connected in series with the load
Feedback
The correct answer is: over load relay is connected in series and no volt relay in parallel
with the load
Question 34
In case of conductively compensated D.C. series motors, the compensating winding is
provided
Select one:
a. as separately wound unit
b. in series with armature winding
c. in parallel with field winding

d. in parallel with armature winding
Feedback
The correct answer is: in series with armature winding
Question 35
In case of D.C. shunt motors the speed is dependent on back e.m.f. only because
Select one:
a. armature drop is negligible
b. flux is proportional to armature current
c. back e.m.f. is equal to armature drop

d. flux is practically constant in D:C. shunt motors
Feedback
The correct answer is: flux is practically constant in D:C. shunt motors
Question 36
In case-the conditions for maximum power for a D.C. motor are established, the
efficiency of the motor will be
Select one:
a. around 90%
b. 100%
c. less than 50%

d. anywhere between 75% and 90%
Feedback
The correct answer is: less than 50%
Question 37
In D.C. shunt motors as load is reduced
Select one:
a. the speed will increase abruptly
b. the speed will remain almost/constant

c. the speed will increase in proportion to reduction in load
d. the speed will reduce
Feedback
The correct answer is: the speed will remain almost/constant
Question 38
In D.C. machines fractional pitch winding is used
Select one:
a. to reduce the sparking
b. to increase the generated e.m.f.
c. to improve cooling
d. to reduce copper losses
Feedback
The correct answer is: to reduce the sparking
Question 39
In D.C. motor which of the following can sustain the maximum temperature rise?
Select one:
a. Commutator
b. Slip rings
c. Field winding
d. Armature winding
Feedback
The correct answer is: Field winding
Question 40
In Ward-Leonard control the lower limit of speed is imposed by
Select one:
a. mechanical losses of motor and generator together
b. core losses of motor
c. all of the above

d. residual magnetism of the generator
Feedback
The correct answer is: residual magnetism of the generator
Question 41
No-load speed of which of the following motor will be highest ?
Select one:
a. Differentiate compound motor
b. Series motor
c. Shunt motor
d. Cumulative compound motor
Feedback
Question 42
Regenerative method of braking is based on that
Select one:
a. back e.m.f. of rotor is more than the applied voltage
b. back e.m.f. is equal to the applied voltage
c. back e.m.f. is less than the applied voltage

d. none of the above
Feedback
The correct answer is: back e.m.f. is equal to the applied voltage
Question 43
Sparking at the commutator of a D.C. motor may result in
Select one:
a. all of the above
b. damage to commutator insulation
c. increased power consumption

d. damage to commutator segments
Feedback
Question 44
Speed control by Ward Leonard method gives uniform speed variation
Select one:
a. in both directions
b. above normal speed only.

c. in one direction
d. below normal speed only
Feedback
The correct answer is: in both directions
Question 45
Starters are used with D.C. motors because
Select one:
a. back e.m.f. of these motors is zero initially
b. these motors are not self-starting
c. to restrict armature current as there is no back e.m.f. while starting

d. these motors have high starting torque
Feedback
The correct answer is: to restrict armature current as there is no back e.m.f. while
starting
Question 46
The armature torque of the D.C. shunt motor is proportional to
Select one:
b. field flux only

c. armature current only
d. both A. and B.
Feedback
The correct answer is: armature current only
Question 47
The armature voltage control of D.C. motor provides
Select one:
a. constant voltage drive
b. constant torque drive
c. constant current drive

Feedback
The correct answer is: constant torque drive
Question 48
The condition for maximum efficiency for a D.C. generator is
Select one:
a. hysteresis losses = eddy current losses
b. eddy current losses = stray losses

c. copper losses = 0
d. variable losses = constant losses
Feedback
The correct answer is: variable losses = constant losses
Question 49
The current drawn by the armature of D.C. motor is directly proportional to
Select one:
a. the voltage across the terminals
c. the speed of the motor

d. the torque required
Feedback
The correct answer is: the torque required
Question 50
The losses occurring in a D.C. generator are given below. Which loss is likely to have
highest proportion at rated load of the generator ?
Select one:
a. eddy current loss
b. hysteresis loss
c. armature copper loss

d. field copper loss
Feedback
The correct answer is: armature copper loss
Question 51
The main disadvantage of the Ward-Leonard control method is
Select one:
a. all of the above

b. low efficiency at Hght loads
c. high maintenance cost
d. high initial cost
Feedback
Question 52
The mechanical power developed by a shunt motor will be maximum when the ratio of
back e.m.f. to applied voltage is
Select one:
a. 4.0
b. 0.5
c. 2.0
d. 1.0
Feedback
The correct answer is: 0.5
Question 53
The plugging gives the
Select one:
a. zero torque braking
b. highest torque braking

d. smallest torque braking
Feedback
The correct answer is: highest torque braking
Question 54
The speed of a D.C. series motor is
Select one:
a. proportional to field current
b. inversely proportional to the armature current
c. proportional to the armature current

d. proportional to the square of the armature current
Feedback
The correct answer is: inversely proportional to the armature current
Question 55
The speed of a D.C. shunt motor can be increased by
Select one:
a. reducing the resistance in the armature circuit
b. increasing the resistance in field circuit
c. increasing the resistance in armature circuit

d. reducing the resistance in the field circuit
Feedback
The correct answer is: increasing the resistance in field circuit
Question 56
The starting resistance of a D.C. motor is generally
Select one:
a. infinitely large
b. around 500 Q
c. 1000 Q
d. low
Feedback
The correct answer is: low
Question 57
The total losses in a well designed D.C. generator of 10 kW will be nearly
Select one:
a. 100 W
b. 500 W
c. 1500 W
d. 1000 W
Feedback
The correct answer is: 500 W
Question 58
The type of D.C. motor used for shears and punches is
Select one:
a. shunt motor
b. differential compoutid D.C. motor
c. cumulative compound D.C. motor

d. series motor
Feedback
The correct answer is: cumulative compound D.C. motor
Question 59
These days D.C. motors are widely used in
Select one:
a. machine shops
b. pumping sets
c. air compressors
d. electric traction
Feedback
The correct answer is: electric traction
Question 60
Three point starter can be used for
Select one:
a. shunt motor only
b. compound motor only
c. series motor only
d. both shunt and compound motor

Feedback
The correct answer is: both shunt and compound motor
Question 61
Torque developed by a D.C. motor depends upon
Select one:
a. current flow through the conductors
b. active length of the conductor
c. all above factors

d. magnetic field
Feedback
The correct answer is: all above factors
Question 62
Usually wide and sensitive speed control is desired in case of
Select one:
a. elevators
b. centrifugal pumps
c. steel rolling mills

d. colliery winders
Feedback
The correct answer is: colliery winders
Question 63
Ward-Leonard control is basically a
Select one:
a. armature resistance control method
b. field divertor method
c. voltage control method

d. field control method
Feedback
The correct answer is: voltage control method
Question 64
What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
Select one:
a. The motor will stop
b. The armature may burn
c. The motor will run noisy

d. The motor will continue to run
Feedback
The correct answer is: The armature may burn
Question 65
When two D.C. series motors are connected in parallel, the resultant speed is
Select one:
a. loss than the normal speed
b. normal speed
c. zero
d. more than the normal speed
Feedback
The correct answer is: normal speed
Question 66
Which D.C. motor is preferred for elevators ?
Select one:
a. Differential compound motor
b. Series motor
c. Cumulative compound motor

d. Shunt motor
Feedback
The correct answer is: Cumulative compound motor
Question 67
Which motor has the poorest speed control?
Select one:
a. Differentially compounded motor
b. Cumulatively compounded motor

c. Series motor
d. Shunt motor
Feedback
Question 68
Which motor should not be started on no-load ?
Select one:
a. Shunt motor
b. Differentially compounded motor.

c. Series motor
d. Cumulatively compounded motor
Feedback
Question 69
Which of the following application requires high starting torque ?
Select one:
a. Lathe machine
b. Air blower
c. Locomotive
d. Centrifugal pump
Feedback
The correct answer is: Locomotive
Question 70
Which of the following law/rule can he used to determine the direction of rotation of
D.C. motor ?
Select one:
a. Fleming's left-hand rule
b. Lenz's law
c. Faraday's law
d. Coloumb's law
Feedback
The correct answer is: Fleming's left-hand rule
Question 71
Which of the following loss in a D.C. generator varies significantly with the load current ?
Select one:
a. Windage loss
b. Field copper loss

c. None of the above
d. Armature copper loss
Feedback
The correct answer is: Armature copper loss
Question 72
Which of the following losses are significantly reduced by laminating the core of a D.C.
generator ?
Select one:
a. Copper losses
b. Hysteresis losses
c. Windage losses
d. Eddy current losses
Feedback
The correct answer is: Eddy current losses
Question 73
Which of the following motor has the poorest speed regulation ?
Select one:
a. Series motor
b. Cumulative compound motor
c. Shunt motor
d. Differential compound motor
Feedback
Question 74
Which of the following motors is most suitable for signalling devices and many kinds of
timers ?
Select one:
a. D.C. shunt motor
b. Reluctance motor
c. Induction motor
Feedback
The correct answer is: Reluctance motor
Question 75
Which of the following motors is usually used in house-hold refrigerators ?
Select one:
a. Reluctance motor
b. D.C. series motor
c. Single phase induction motor (split phase start or induction run motor)
d. D.C. shunt motor
Feedback
The correct answer is: Single phase induction motor (split phase start or induction run
motor)
Question 76
Which of the following tests will be suitable for testing two similar D.C. series motors of
large capacity ?
Select one:
a. Field test
b. Hopkinson's test
c. Brake test
d. Swinburne's test
Feedback
The correct answer is: Field test
Question 77
Which one of the following is not necessarily the advantage of D.C. motors over A.C.
motors ?
Select one:
a. Low cost
b. Wide speed range
c. Stability
d. High starting torque.
Feedback
The correct answer is: Low cost
Question 78
Why are the D.C. motors preferred for traction applications ?
Select one:
a. Torque and speed are inversely proportional to armature current
b. The speed is inversely proportional to the torque and the torque is proportional to
square of armature current
c. Torque is proportional to armature current

d. Torque is proportional to square root of armature current
Feedback
The correct answer is: The speed is inversely proportional to the torque and the torque
is proportional to square of armature current
Question 1
A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor e.m.f. will be
Select one:
a. 0.2 Hz
b. 50 Hz
c. 200 Hz
d. 2 Hz
Feedback
The correct answer is: 2 Hz
Question 2
A 3-phase induction motor stator delta connected, is carrying full load and one of its
fuses blows out. Then the motor
Select one:
a. will stop and carry heavy current causing permanent damage to its winding
b. will continue running without any harm to the winding
c. will continue running burning its two phases

d. will continue running burning its one phase
Feedback
The correct answer is: will continue running burning its one phase
Question 3
A 3-phase slip ring motor has
Select one:
a. double cage rotor
b. wound rotor
c. short-circuited rotor
d. any of the above
Feedback
The correct answer is: wound rotor
Question 4
A 500 kW, 3-phase, 440 volts, 50 Hz, A.C. induction motor has a speed of 960 r.p.m. on
full load. The machine has 6 poles. The slip of the machine will be
Select one:
a. 0.03
b. 0.01
c. 0.04
d. 0.02
Feedback
The correct answer is: 0.04
Question 5
A change of 4% of supply voltage to an induction motor will produce a change of
appromimately
Select one:
a. 8% in the rotor torque
b. 16% in the rotor torque
c. 12% in the rotor torque

d. 4% in the rotor torque
Feedback
The correct answer is: 16% in the rotor torque
Question 6
A double squirrel-cage induction motor has
Select one:
a. two parallel windings in rotor
b. two rotors moving in oppsite direction
c. two parallel windings in stator

d. two series windings in stator
Feedback
The correct answer is: two parallel windings in rotor
Question 7
A squirrel cage induction motor is not selected when
Select one:
a. initial cost is the main consideration
b. maintenance cost is to be kept low

c. all above considerations are involved
d. higher starting torque is the main consideration
Feedback
The correct answer is: higher starting torque is the main consideration
Question 8
An induction motor can run at synchronous speed when
Select one:
a. it is run on voltage higher than the rated voltage
b. e.m.f. is injected in the rotor circuit

c. it is run in reverse direction
d. it is run on load
Feedback
The correct answer is: e.m.f. is injected in the rotor circuit
Question 9
An induction motor is
Select one:
a. self-starting with high torque
b. self-starting with zero torque

c. non-self starting
d. self-starting with low torque
Feedback
The correct answer is: self-starting with low torque
Question 10
An induction motor is identical to
Select one:
a. D.C. compound motor
b. D.C. series motor
c. asynchronous motor
d. synchronous motor
Feedback
The correct answer is: asynchronous motor
Question 11
An induction motor with 1000 r.p.m. speed will have
Select one:
a. 8 poles
b. 6 poles
c. 2 poles
d. 4 poles
Feedback
The correct answer is: 6 poles
Question 12
As load on an induction motor goes on increasing
Select one:
a. its power factor goes on increasing even after full load
b. its power factor goes on increasing up to full load and then it falls again
c. its power factor remains constant

d. its power factor goes on decreasing
Feedback
The correct answer is: its power factor goes on increasing up to full load and then it falls
again
Question 13
considered
Select one:
a. in parallel
b. in series
c. in series-parallel
d. in parallel with stator
Feedback
The correct answer is: in parallel
Question 14
following machines
Select one:
b. D.C. shunt motor
c. universal motor
Feedback
The correct answer is: D.C. shunt motor
Question 15
For driving high inertia loods best type of induction motor suggested is
Select one:
a. any of the above
c. slip ring type

d. squirrel cage type
Feedback
The correct answer is: slip ring type
Question 16
For which motor the speed can be controlled from rotor side ?
Select one:
a. Squirrel-cage induction motor
b. None of the above

c. Both A. and B.
d. Slip-ring induction motor
Feedback
The correct answer is: Slip-ring induction motor
Question 17
If a 3-phase supply is given to the stator and rotor is short circuited rotor will move
Select one:
a. in the opposite direction as the direction of the rotating field
b. in the same direction as the direction of the field

c. in any direction depending upon phase squence of supply
Feedback
The correct answer is: in the same direction as the direction of the field
Question 18
If an induction motor with certain ratio of rotor to stator slots, runs at 1/7 of the normal
speed, the phenomenon will be termed as
Select one:
a. crawling
b. cogging
c. humming
d. hunting
Feedback
The correct answer is: crawling
Question 19
If any two phases for an induction motor are interchanged
Select one:
a. the motor will run at reduced speed
b. the motor will not run
c. the motor will run in reverse direction

d. the motor will burn
Feedback
The correct answer is: the motor will run in reverse direction
Question 20
In a squirrel cage motor the induced e.m.f. is
Select one:
a. dependent on the shaft loading
b. dependent on the number of slots

d. slip times the stand still e.m.f. induced in the rotor
Feedback
The correct answer is: slip times the stand still e.m.f. induced in the rotor
Question 21
In a star-delta starter of an induction motor
Select one:
a. resistance is inserted in the rotor
b. resistance is inserted in the stator
c. applied voltage perl stator phase is 57.7% of the line voltage

d. reduced voltage is applied to the stator
Feedback
The correct answer is: applied voltage perl stator phase is 57.7% of the line voltage
Question 22
In a three-phase induction motor
Select one:
a. iron losses in stator will be more than that in rotor
b. iron losses in stator will be negligible as compared to that in rotor
c. iron losses in stator will be less than that in rotor

Feedback
The correct answer is: iron losses in stator will be more than that in rotor
Question 23
In a three-phase induction motor
Select one:
a. power factor at starting in the same as that while running
b. power factor at starting is high as compared to that while running

c. power factor at starting is low as compared to that while running
Feedback
The correct answer is: power factor at starting is low as compared to that while running
Question 24
In a three-phase induction motor, the number of poles in the rotor winding is always
Select one:
a. equal to number of poles in stator
b. less than number of poles in stator

c. more than the number of poles in stator
d. zero
Feedback
The correct answer is: equal to number of poles in stator
Question 25
In an induction motor if air-gap is increased
Select one:
a. the power factor will be low
b. copper loss will reduce In an induction motor
c. windage losses will be more

d. bearing friction will reduce
Feedback
The correct answer is: the power factor will be low
Question 26
In an induction motor the relationship between stator slots and rotor slots is that
Select one:
b. stator slots are exact multiple of rotor slots
c. stator slots are equal to rotor slots

d. stator slots are not exact multiple of rotor slots
Feedback
The correct answer is: stator slots are not exact multiple of rotor slots
Question 27
In an induction motor, no-load the slip is generally
Select one:
a. less than 1%
b. 4%
c. 1.5%
d. 2%
Feedback
The correct answer is: less than 1%
Question 28
In case of a double cage induction motor, the inner cage has
Select one:
a. low inductance and low resistance
b. low inductance and high resistance
c. high inductance and high resistance

d. high inductance arid low resistance
Feedback
The correct answer is: high inductance arid low resistance
Question 29
In case of the induction motors the torque is
Select one:
a. inversely proportional to slip
b. inversely proportional to (Vslip)
c. directly proportional to slip

d. directly proportional to (slip)2
Feedback
The correct answer is: directly proportional to slip
Question 30
In case the air gap in an induction motor is increased
Select one:
a. the windage losses will increase
b. the power factor will decrease
c. speed of motor will increase

d. the magnetising current of the rotor will decrease
Feedback
The correct answer is: the power factor will decrease
Question 31
In induction motor, percentage slip depends on
Select one:
a. supply frequency
b. copper losses in motor
c. supply voltage
Feedback
The correct answer is: copper losses in motor
Question 32
In medium sized induction motors, the slip is generally around
Select one:
a. 14%
b. 0.04%
c. 4%
d. 0.4%
Feedback
The correct answer is: 4%
Question 33
In Ns is the synchronous speed and s the slip, then actual running speed of an induction
motor will be
Select one:
a. (l-s)Ns
b. s.N,
c. Ns
d. (Ns-l)s
Feedback
The correct answer is: (l-s)Ns
Question 34
In squirrel cage induction motors, the rotor slots are usually given slight skew in order
to
Select one:
a. reduce accumulation of dirt and dust
b. reduce windage losses
c. reduce eddy currents

d. reduce magnetic hum
Feedback
The correct answer is: reduce magnetic hum
Question 35
In the squirrel-cage induction motor the rotor slots are usually given slight skew
Select one:
b. to increase the tensile strength of the rotor bars
c. to reduce the magnetic hum and locking tendency of the rotor

d. to ensure easy fabrication
Feedback
The correct answer is: to reduce the magnetic hum and locking tendency of the rotor
Question 36
In three-phase induction motors sometimes copper bars are placed deep in the rotor to
Select one:
a. improve starting torque
b. improve power factor
c. improve efficiency
d. reduce copper losses
Feedback
The correct answer is: improve starting torque
Question 37
In three-phase squirrel-cage induction motors
Select one:
a. rotor conductors are kept open
b. rotor conductors are connected to insulation
c. rotor conductors are short-circuited through end rings

d. rotor conductor ends are short-circuited through slip rings
Feedback
The correct answer is: rotor conductors are short-circuited through end rings
Question 38
It is advisable to avoid line starting of induction motor and use starter because
Select one:
a. starting torque is very high
b. motor takes five to seven times its full load current
c. it will pick up very high speed and may go out of step
d. it will run in reverse direction

Feedback
The correct answer is: motor takes five to seven times its full load current
Question 39
It is advisable to avoid line-starting of induction motor and use starter because
Select one:
a. it will pick-up very high speed and may go out of step
b. starting torque is very high
c. motor takes five to seven times its full load current

Feedback
Question 40
Less maintenance troubles are experienced in case of
Select one:
a. both A. and B.
b. squirrel cage induction motor
c. slip ring induction motor

Feedback
The correct answer is: squirrel cage induction motor
Question 41
Low voltage at motor terminals is due to
Select one:
b. any one of the above
c. inadequate motor wiring

d. poorely regulated power supply
Feedback
The correct answer is: any one of the above
Question 42
Lubricant used for ball bearing is usually
Select one:
a. grease
b. mineral oil
c. graphite
d. molasses
Feedback
The correct answer is: grease
Question 43
motor
Select one:
a. will continue running burning its two phase
b. will stop and carry heavy current causing permanent damage to its winding
c. will continue running burning its one phase

d. will continue running without any harm to the winding
Feedback
The correct answer is: will stop and carry heavy current causing permanent damage to
its winding
Question 44
Short-circuit test on an induction motor cannot be used to determine
Select one:
a. windage losses
b. copper losses
c. power scale of circle diagram

d. transformation ratio
Feedback
The correct answer is: windage losses
Question 45
Size of a high speed motor as compared to low speed motor for the same H.P. will be
Select one:
a. bigger
b. same
c. smaller
d. any of the above
Feedback
The correct answer is: smaller
Question 46
Slip ring motor is preferred over squirrel cage induction motor where
Select one:
a. high starting torque is required
b. load torque is heavy
c. all of the above

d. heavy pull out torque is required
Feedback
The correct answer is: high starting torque is required
Question 47
Slip ring motor is recommended where
Select one:
a. frequent starting, stopping and reversing is required
b. all above features are required
c. speed control is required

d. high starting torque is needed
Feedback
The correct answer is: all above features are required
Question 48
Slip rings are usually made of
Select one:
a. phospor bronze
b. carbon
c. copper
d. aluminium
Feedback
The correct answer is: phospor bronze
Question 49
Star-delta starting of motors is not possible in case of
Select one:
a. single phase motors
b. low horse power motors

c. high speed motors
d. variable speed motors
Feedback
The correct answer is: single phase motors
Question 50
Stepless speed control of induction motor is possible by which of the following methods
?
Select one:
a. e.m.f. injection in rotor eueuit
b. Cascade operation
d. Changing the number of poles
Feedback
The correct answer is: Changing the number of poles
Question 51
Temperature of the stator winding of a three phase induction motor is obtained by
Select one:
a. thermometer method
b. all above methods
c. embedded temperature method

d. resistance rise method
Feedback
The correct answer is: all above methods
Question 52
The torque developed in the cage induction motor with autostarter is
Select one:
a. K x torque with direct switching
b. k/torque with direct switching
c. k2/torque with direct switching

d. K2 x torque with direct switching
Feedback
The correct answer is: K2 x torque with direct switching
Question 53
The complete circle diagram of induetion motor can be drawn with the help of data
found from
Select one:
a. blocked rotor test
b. noload test
c. stator resistance test

d. all of the above
Feedback
Question 54
The efficiency of an induction motor can be expected to be nearly
Select one:
a. 95 to 98%
b. 99%
c. 80 to 90%
d. 60 to 90%
Feedback
The correct answer is: 80 to 90%
Question 55
The frame of an induction motor is usually made of
Select one:
a. bronze
b. aluminium
c. cast iron
d. silicon steel
Feedback
The correct answer is: cast iron
Question 56
The good power factor of an induction motor can be achieved if the average flux density
in the air gap is
Select one:
a. large
b. small
c. absent
d. infinity
Feedback
The correct answer is: small
Question 57
The injected e.m.f. in the rotor of induction motor must have
Select one:
a. zero frequency
b. high value for the satisfactory speed control
c. the same frequency as the slip frequency

d. the same phase as the rotor e.m.f.
Feedback
The correct answer is: the same frequency as the slip frequency
Question 58
The low power factor of induction motor is due to
Select one:
a. rotor leakage reactance
b. all of the above
c. stator reactance
d. the reactive lagging magnetizing current necessary to generate the magnetic flux
Feedback
Question 59
The maximum torque in an induction motor depends on
Select one:
a. frequency
b. all of the above

c. square of supply voltage
d. rotor inductive reactance
Feedback
Question 60
The number of slip rings on a squirrel cage induction motor is usually
Select one:
a. four
b. three
c. none
d. two
Feedback
The correct answer is: none
Question 61
The power factor of an induction motor under no-load conditions will be closer to
Select one:
a. unity
b. 0.5 leading
c. 0.2 leading
d. 0.2 lagging
Feedback
The correct answer is: 0.2 lagging
Question 62
The power scale of circle diagram of an induction motor can be found from
Select one:
a. noue of the above
b. no-load test only

c. short-circuit test only
d. stator resistance test
Feedback
The correct answer is: short-circuit test only
Question 63
I
The purpose of using short-circuit gear is
Select one:
a. to short circuit the starting resistances in the starter
b. to short circuit the rotor at slip rings

d. to short circuit the stator phase of motor to form star
Feedback
The correct answer is: to short circuit the rotor at slip rings
Question 64
The rotor of an induction motor runs at
Select one:
a. any of the above
b. below synchronous speed
c. above synchronous speed
d. synchronous speed
Feedback
The correct answer is: below synchronous speed
Question 65
The shaft of an induction motor is made of
Select one:
a. any of the above
b. stiff
c. hollow
d. flexible
Feedback
The correct answer is: stiff
Question 66
The shaft of an induction motor is made of
Select one:
a. cast iron
b. high speed steel
c. carbon steel
d. stainless steel
Feedback
The correct answer is: carbon steel
Question 67
The shape of the torque/slip curve of induction motor is
Select one:
a. straigth line
b. rectangular parabola
c. hyperbola
d. parabola
Feedback
The correct answer is: rectangular parabola
Question 68
The speed of a squirrel-cage induction motor can be controlled by all of the following
except
Select one:
a. changing number of poles
b. changing winding resistance

c. changing supply frequency
d. reducing supply voltage
Feedback
The correct answer is: changing winding resistance
Question 69
The starting torque of a 3-phase squirrel cage induction motor is
Select one:
a. twice the full load torque
b. 1.5 times the full load torque

c. equal to full load torque
Feedback
The correct answer is: 1.5 times the full load torque
Question 70
The starting torque of a squirrel-cage induction motor is
Select one:
a. slightly more than full-load torque
b. same as full-load torque
c. negligible
d. low
Feedback
The correct answer is: low
Question 71
The starting torque of a three phase induction motor can be increased by
Select one:
a. increasing slip
b. increasing current
c. both A. and B.
Feedback
The correct answer is: both A. and B.
Question 72
The stating torque of the slip ring induction motor can be increased by adding
Select one:
a. external inductance to the rotor
b. external capacitance to the rotor

c. both resistance and inductance to rotor
d. external resistance to the rotor
Feedback
The correct answer is: external resistance to the rotor
Question 73
The term 'cogging' is associated with
Select one:
a. compound generators
b. D.C. series motors
c. three phase transformers

d. induction motors
Feedback
The correct answer is: induction motors
Question 74
The torque developed by a 3-phase induction motor least depends on
Select one:
a. rotor current
b. rotor power factor
c. rotor e.m.f.
d. shaft diameter
Feedback
The correct answer is: shaft diameter
Question 75
The torque of a rotor in an induction motor under running condition is maximum
Select one:
a. at the unit value of slip
b. at the value of the slip which makes rotor reactance per phase equal to the resistance
per phase
c. at the value of the slip which makes the rotor reactance half of the rotor
d. at the zero value of slip
Feedback
The correct answer is: at the value of the slip which makes rotor reactance per phase
equal to the resistance per phase
Question 76
The torque of an induction motor is
Select one:
b. proportional to the square of the slip
c. directly proportional to slip

d. inversely proportional to slip
Feedback
The correct answer is: directly proportional to slip
Question 77
The vafcie of transformation ratio of an induction motor can be found by
Select one:
a. stator resistance test
b. open-circuit test only

d. short-circuit test only
Feedback
The correct answer is: short-circuit test only
Question 78
What will happen if the relative speed between the rotating flux of stator and rotor of
the induction motor is zero ?
Select one:
a. The rotor will not run
b. The torque produced will be very large
c. The rotor will run at very high speed
d. The slip of the motor will be 5%

Feedback
The correct answer is: The rotor will not run
Question 79
Which is of the following data is required to draw the circle diagram for an induction
motor ?
Select one:
a. No load test only
b. Block rotor test only
c. Block rotor test, no-load test and stator resistance test

d. Block rotor test and no-load test
Feedback
The correct answer is: Block rotor test, no-load test and stator resistance test
Question 80
Which motor is preferred for use in mines where explosive gases exist ?
Select one:
a. Induction motor
b. Synchronous motor
c. Air motor
d. D.C. shunt motor
Feedback
The correct answer is: Air motor
Question 81
Which of the following component is usually fabricated out of silicon steel ?
Select one:
a. Bearings
b. Statorcore
d. Shaft
Feedback
The correct answer is: Statorcore
Question 82
Which of the following methods is easily applicable to control the speed of the squirrel-
cage induction motor ?
Select one:
a. Rotor rheostat control
b. By injecting e.m.f. in the rotor circuit
c. By operating two motors in cascade
d. By changing the number of stator poles

Feedback
The correct answer is: By changing the number of stator poles
Question 83
Which type of bearing is provided in small induction motors to support the rotor shaft ?
Select one:
a. Ball bearings
b. Cast iron bearings
c. Bush bearings
d. None of the above

Feedback
The correct answer is: Ball bearings
Question 1
As load on an induction motor goes on increasing
Select one:
a. its power factor goes on increasing up to full load and then it falls again
b. its power factor remains constant

c. its power factor goes on decreasing
d. its power factor goes on increasing even after full load
Feedback
The correct answer is: its power factor goes on increasing up to full load and then it falls
again
Question 2
Blocked rotor test on induction motors is used to find out
Select one:
a. all of the above
b. short-circuit current under rated voltage
c. power factor on short circuit

d. leakage reactance
Feedback
Question 3
DOL starting of induction motors is usually restricted to
Select one:
a. high horsepower motors
b. low horsepower motors

c. variable speed motors
d. high speed motors
Feedback
The correct answer is: low horsepower motors
Question 4
For driving high inertia loods best type of induction motor suggested is
Select one:
a. slip ring type
b. any of the above

c. squirrel cage type
Feedback
The correct answer is: slip ring type
Question 5
For which motor the speed can be controlled from rotor side ?
Select one:
a. Slip-ring induction motor
c. Squirrel-cage induction motor

d. Both A. and B.
Feedback
The correct answer is: Slip-ring induction motor
Question 6
If a 3-phase supply is given to the stator and rotor is short circuited rotor will move
Select one:
a. in any direction depending upon phase squence of supply

b. in the opposite direction as the direction of the rotating field
c. in the same direction as the direction of the field
Feedback
The correct answer is: in the same direction as the direction of the field
Question 7
In a star-delta starter of an induction motor
Select one:
a. reduced voltage is applied to the stator
b. resistance is inserted in the rotor
c. resistance is inserted in the stator

d. applied voltage perl stator phase is 57.7% of the line voltage
Feedback
The correct answer is: applied voltage perl stator phase is 57.7% of the line voltage
Question 8
In an induction motor if air-gap is increased
Select one:
a. bearing friction will reduce
b. copper loss will reduce In an induction motor
c. windage losses will be more

d. the power factor will be low
Feedback
The correct answer is: the power factor will be low
Question 9
In induction motor, percentage slip depends on
Select one:
b. supply voltage
c. copper losses in motor
d. supply frequency
Feedback
The correct answer is: copper losses in motor
Question 10
In the circle diagram for induction motor, the diameter of the circle represents
Select one:
a. slip
b. line voltage
c. rotor current
d. running torque
Feedback
The correct answer is: rotor current
Question 11
In three-phase squirrel-cage induction motors
Select one:
a. rotor conductor ends are short-circuited through slip rings
b. rotor conductors are short-circuited through end rings
c. rotor conductors are connected to insulation

d. rotor conductors are kept open
Feedback
The correct answer is: rotor conductors are short-circuited through end rings
Question 12
Insertion of resistance in the rotcir of an induction motor to develop a given torque
Select one:
a. decreases the rotor current
b. increases the rotor current
c. rotor current becomes zero

d. rotor current rernains same
Feedback
The correct answer is: rotor current rernains same
Question 13
It is advisable to avoid line starting of induction motor and use starter because
Select one:
a. starting torque is very high
b. it will pick up very high speed and may go out of step
c. motor takes five to seven times its full load current

Feedback
Question 14
Reduced voltage starter can be used with
Select one:
a. squirrel cage induction motor only but not with slip ring motor
b. slip ring motor only but not with squirrel cage induction motor

d. squirrel cage as well as slip ring induction motor
Feedback
The correct answer is: squirrel cage as well as slip ring induction motor
Question 15
Rotor rheostat control method of speed control is used for
Select one:
a. squirrel-cage induction motors only
b. both A. and B.
c. slip ring induction motors only

Feedback
The correct answer is: slip ring induction motors only
Question 16
Short-circuit test on an induction motor cannot be used to determine
Select one:
a. copper losses
b. power scale of circle diagram
c. transformation ratio
d. windage losses
Feedback
The correct answer is: windage losses
Question 17
Star-delta starting of motors is not possible in case of
Select one:
a. high speed motors
b. variable speed motors
c. low horse power motors
d. single phase motors

Feedback
The correct answer is: single phase motors
Question 18
Stepless speed control of induction motor is possible by which of the following methods
?
Select one:
a. Changing the number of poles

c. Cascade operation
d. e.m.f. injection in rotor eueuit
Feedback
The correct answer is: Changing the number of poles
Question 19
Temperature of the stator winding of a three phase induction motor is obtained by
Select one:
a. embedded temperature method
b. all above methods
c. resistance rise method
d. thermometer method
Feedback
The correct answer is: all above methods
Question 20
The 'cogging' of an induction motor can be avoided by
Select one:
a. using DOL starter
b. having number of rotor slots more or less than the number of stator slots (not equal)
c. auto-transformer starter
d. proper ventilation
Feedback
The correct answer is: having number of rotor slots more or less than the number of
stator slots (not equal)
Question 21
The 'crawling" in an induction motor is caused by
Select one:
a. low voltage supply
b. improper design of machine
c. high loads
d. harmonics developed in the motor
Feedback
The correct answer is: harmonics developed in the motor
Question 22
The auto-starters (using three auto transformers) can be used to start cage induction
motor of the following type
Select one:
b. A. and B. both
c. star connected only

d. delta connected only
Feedback
The correct answer is: A. and B. both
Question 23
The circle diagram for an induction motor cannot be used to determine
Select one:
a. output
b. frequency
c. power factor
d. efficiency
Feedback
The correct answer is: efficiency
Question 24
The complete circle diagram of induetion motor can be drawn with the help of data
found from
Select one:
a. blocked rotor test
b. noload test
c. stator resistance test
d. all of the above
Feedback
Question 25
The low power factor of induction motor is due to
Select one:
a. stator reactance
b. all of the above
c. the reactive lagging magnetizing current necessary to generate the magnetic flux
d. rotor leakage reactance
Feedback
Question 26
The number of slip rings on a squirrel cage induction motor is usually
Select one:
a. none
b. three
c. four
d. two
Feedback
The correct answer is: none
Question 27
What will happen if the relative speed between the rotating flux of stator and rotor of
the induction motor is zero ?
Select one:
a. The torque produced will be very large

b. The rotor will not run
c. The slip of the motor will be 5%
d. The rotor will run at very high speed
Feedback
The correct answer is: The rotor will not run
Question 28
When R2 is the rotor resistance, X2 the rotor reactance at supply frequency and s the
slip, then the condition for maximum torque under running conditions will be
Select one:
a. sR2 = X2
b. R2 = sX2
c. R2 = s2X2
d. sR2X2 = 1
Feedback
The correct answer is: R2 = sX2
Question 29
Which is of the following data is required to draw the circle diagram for an induction
motor ?
Select one:
a. Block rotor test, no-load test and stator resistance test
b. No load test only
c. Block rotor test and no-load test

d. Block rotor test only
Feedback
The correct answer is: Block rotor test, no-load test and stator resistance test
Question 1
1. A transformer transforms ?
Select one:
a. Voltage.
b. Both A and B.
c. None of these.
d. Current.
Feedback
The correct answer is: Both A and B.
Question 2
1. Laminations of core are generally made of
Select one:
a. stainless steel.
b. castiron.
c. silicon steel.
d. carbon.
Feedback
The correct answer is: stainless steel.
Question 3
10. A transformer transfers ---- without change.
Select one:
a. Frequency
b. Both A and B
c. Current
d. Voltage
Feedback
The correct answer is: Frequency
Question 4
27. In a relation to transformer, 17:1 indicates that
Select one:
a. Secondary voltage is 1/17th of primary voltage
b. There are 17 turns on primary and 1 turn on secondary
c. For every 17 turns on primary, there is 1 turn on secondary

d. Primary current is 17 times greater than the secondary current
Feedback
The correct answer is: For every 17 turns on primary, there is 1 turn on secondary
Question 5
29. A transformer having 1250 primary turns, is connected to a 200V AC supply. For a
secondary voltage of 400V, the number of secondary turns should be?
Select one:
a. 2500
b. 1600
c. 1250
d. 400
Feedback
The correct answer is: 2500
Question 6
3. In case of a transformer, the primary & secondary windings are wound on a same
limb, so as to reduce ?
Select one:
a. Leakage reactance
b. None of these
c. Self induction
d. Mutual induction
Feedback
The correct answer is: Leakage reactance
Question 7
3. Transformer is used for
Select one:
a. to step up and step down primary voltage.

b. to step down voltage.
c. None of above.
d. to step up voltage.
Feedback
The correct answer is: to step up and step down primary voltage.
Question 8
30. The rating of transformer is given in terms of
Select one:
a. None of these
b. True power
c. Reactive power
d. Apparent power
Feedback
The correct answer is: Apparent power
Question 9
32.At No load , following losses are negligible
Select one:
a. Eddy current loss
b. Iron loss
c. Copper loss
d. Hysteresis loss
Feedback
The correct answer is: Copper loss
Question 10
33. The transformation ratio (k) means
Select one:
a. I1/ I2
b. V2 / V1
c. N2 / N1
d. All of these
Feedback
The correct answer is: All of these
Question 11
34. The copper saving in case of auto-transformer is
Select one:
a. Weight of 2 winding transformer / k
b. k / weight of 2 winding transformer
c. (1-k) x weight of 2 winding transformer
d. k x weight of 2 winding transformer

Feedback
The correct answer is: k x weight of 2 winding transformer
Question 12
Select one:
a. 400
b. 1600
c. 900
d. 250
Feedback
Question 13
38. The No Load primary current is the phasor sum of
Select one:
a. Both A & B
b. Magnetizing component of No Load current
c. None of these
d. Loss component of No Load current
Feedback
The correct answer is: Both A & B
Question 14
Correct
Mark 1.00 out of 1.00
Flag question
Question text
39. The phenomenon of the self induction and mutual induction is felt, only when the
current in the coil is of ------ nature.
Select one:
a. DC
b. AC
c. None of above
d. Both of above
Feedback
The correct answer is: AC
Question 15
4. Breather is provided in a transformer to.
Select one:
a. Absorb moisture of air during breathing.

b. filter of transformer oil.
c. provide cold air in transformer.
d. DC generator
Feedback
The correct answer is: Absorb moisture of air during breathing.
Question 16
4. In case of which of the following equipment, the EMF induced is due to static
induction?
Select one:
a. DC motor
b. DC generator
c. DC generator
d. Transformer
Feedback
The correct answer is: Transformer
Question 17
40. The equivalent resistance (R2e) referred to secondary side is
Select one:
a. R2 + (R1 . k 2)
b. R2 + (R1 / k 2)
c. R1 + (R2 . k 2)
d. R1 + (R2 / k 2)
Feedback
The correct answer is: R2 + (R1 . k 2)
Question 18
45. The primary and secondary induced EMF's E1 and E2 in a two
Select one:
a. In phase with each other

b. Anti-phase with each other
c. Determined by nature of load on secondary
d. Equal in magnitude
Feedback
The correct answer is: In phase with each other
Question 19
46. Sandwich windings are used for ----- type of transformer.
Select one:
a. Berry
b. Shell
c. None of these
d. Core
Feedback
The correct answer is: Shell
Question 20
48. The equivalent leakage reactance (X1e) referred to primary side is
Select one:
a. X2 + (X1 / k 2)
b. X1 + (X2 . k 2)
c. X2 + (X1 . k 2)
d. X1 + (X2 / k 2)
Feedback
The correct answer is: X1 + (X2 / k 2)
Question 21
52. ------- Losses are called as variable losses.
Select one:
a. Copper loss
b. Iron loss
c. Hysteresis loss + Eddy current loss
d. Both A & B
Feedback
Question 22
53. If the load current is halved, then copper losses will become
Select one:
a. None of these
b. Quarter
c. Remain same
d. Half
Feedback
The correct answer is: Quarter
Question 23
54. A step up transformer decreases
Select one:
a. Frequency
b. Current
c. Voltage
d. Power
Feedback
The correct answer is: Current
Question 24
55. The equivalent leakage reactance (X2e) referred to secondary side is
Select one:
a. X2 + (X1 / k 2)
b. X1 + (X2 . k 2)
c. X2 + (X1 . k 2)
d. X1 + (X2 / k 2)
Feedback
The correct answer is: X2 + (X1 . k 2)
Question 25
60. A step down transformer increases
Select one:
a. Current
b. Voltage
c. Power
d. Frequency
Feedback
Question 26
61. In case of phasor diagram of transformer, phasors for induced EMF's in primary and
secondary windings -------- flux.
Select one:
a. Out of phase with
b. In phase with
c. None of these
d. Lags behind by 900 with

Feedback
The correct answer is: Lags behind by 900 with
Question 27
62. The power factor is unity for purely ------ load.
Select one:
a. Resistive
b. Capacitive
c. Both A & C
d. Inductive
Feedback
The correct answer is: Resistive
Question 28
64. The equivalent impedance (Z1e) referred to primary side is
Select one:
a. Z1 + (Z2 . k 2)
b. Z2 + (Z1 / k 2)
c. Z2 + (Z1 . k 2)
d. Z1 + (Z2 / k 2)
Feedback
The correct answer is: Z1 + (Z2 / k 2)
Question 29
7. The losses obtained in Short Circuit Test are .
Select one:
a. Copper losses
b. Both A & B
c. Hysteresis losses
d. Eddy current losses

Feedback
The correct answer is: Copper losses
Question 30
70. A step down transformer decreases
Select one:
a. Current
b. Frequency
c. Power
d. Voltage
Feedback
The correct answer is: Voltage
Question 1
1. In lap winding, the number of brushes is always
Select one:
a. double the number of poles.
b. half the number of poles.
c. same as the number of poles.

d. Two.
Feedback
The correct answer is: same as the number of poles.
Question 2
10. The insulating material used between the commutator segments is normally ?
Select one:
a. insulating varnish
b. paper
c. graphite
d. mica
Feedback
The correct answer is: mica
Question 3
11. The armature torque of the D.C. shunt motor is proportional to
Select one:
b. both
c. armature current only
d. field flux only
Feedback
The correct answer is: armature current only
Question 4
12. The direction of rotation of a D.C. series motor can be changed by ?
Select one:
a. interchanging field terminals
b. any of the above
c. none
d. interchanging supply terminals
Feedback
The correct answer is: any of the above
Question 5
13. What will happen if the back e.m.f. of a D.C. motor vanishes suddenly
Select one:
a. The motor will continue to run
b. The motor will stop
c. Armature will burn
d. The motor will run noisy

Feedback
The correct answer is: Armature will burn
Question 6
14. In D.C. shunt motors as load is reduced
Select one:
a. the speed will increase in proportion to reduction in load
b. the speed will increase abruptly
c. the speed will remain almost constant

d. the speed will reduce
Feedback
The correct answer is: the speed will remain almost constant
Question 7
15. The type of D.C. motor used for shears and punches is
Select one:
a. shunt motor
b. series motor
c. cumulative compound D.C. motor

d. differential compoutid D.C. motor
Feedback
The correct answer is: shunt motor
Question 8
16. Three point starter can be used for ?
Select one:
a. series motor only
b. compound motor only

c. both shunt and compound motor
d. shunt motor only
Feedback
The correct answer is: both shunt and compound motor
Question 9
17. If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens
Select one:
a. motor will come to stop
b. nothing will happen to motor
c. is will result in excessive speed, possibly destroying armature due to excessive
centrifugal stresses
d. this will make armature to take heavy current, possibly burning it
Feedback
The correct answer is: is will result in excessive speed, possibly destroying armature due
to excessive centrifugal stresses
Question 10
18. The speed of a D.C. shunt motor can be increased by
Select one:
a. reducing the resistance in the field circuit
b. increasing the resistance in armature circuit
c. increasing the resistance in field circuit

d. reducing the resistance in the armature circuit
Feedback
The correct answer is: increasing the resistance in field circuit
Question 11
19. Which D.C. motor will be preferred for machine tools
Select one:
a. Differential compound motor
b. Shunt motor
c. Series motor
d. Cumulative compound motor
Feedback
The correct answer is: Shunt motor
Question 12
2. The commutator segments are connected to the armature conductors by means of
Select one:
a. brazing
b. resistance wires
c. insulation pads
d. copper lugs
Feedback
The correct answer is: copper lugs
Question 13
20. When the armature of a D.C. motor rotates, e.m.f. induced is :
Select one:
a. none of the above.
b. mutually induced e.m.f.
c. self-induced e.m.f
d. back e.m.f.
Feedback
The correct answer is: back e.m.f.
Question 14
3. The armature core of a D.C. generator is usually made of ?
Select one:
a. silicon steel
b. non-ferrous material
c. cast-iron
d. copper
Feedback
The correct answer is: silicon steel
Question 15
4. The function of pole shoes in the case of D.C. machine is
Select one:
a. to support the field coil
b. to discharge all the above functions

c. to reduce the reluctance of the magnetic path
d. to spread out the flux to achieve uniform flux density
Feedback
The correct answer is: to discharge all the above functions
Question 16
5. In a D.C. generator the number of mechanical degrees and electrical degrees will be
the same when
Select one:
a. None of the above
b. number of poles is 2
c. number of poles is 4
d. number of poles is 6
Feedback
The correct answer is: number of poles is 2
Question 17
6. In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral
axis, when :
Select one:
a. the generator runs on full load
c. the generator runs on overload

d. there is no load on the generator
Feedback
The correct answer is: there is no load on the generator
Question 18
7. In a D.C. machine stray loss is the sum of
Select one:
a. shunt field copper loss and mechanical loss
b. armature copper loss and iron loss
c. total copper loss and mechanical loss

d. iron loss and mechanical loss
Feedback
The correct answer is: iron loss and mechanical loss
Question 19
8. A D.C. generator can be considered as .
Select one:
a. primemover
b. power pump
c. rectifier
d. rotating amplifier
Feedback
The correct answer is: rectifier
Question 20
9. Compensating windings are used in D.C. generators .
Select one:
a. to neutralise the cross-magnetising effect of the armature reaction

c. mainly to reduce the eddy currents by providing local short-circuits
d. to provide path for the circulation of cooling air
Feedback
The correct answer is: to neutralise the cross-magnetising effect of the armature
reaction
1. A transformer transforms ?
Select one:
a. Current.
b. Both A and B.
c. Voltage.
d. None of these.
Feedback
The correct answer is: Both A and B.
Question 2
10. A transformer transfers ---- without change.
Select one:
a. Voltage
b. Current
c. Frequency
d. Both A and B
Feedback
The correct answer is: Frequency
Question 3
11. Though the load changes, ----- losses remain same.
Select one:
a. Hysteresis
b. Copper
c. Both A & B
d. Eddy current
Feedback
Question 4
12. Normally open circuit test is carried out on ---- winding, keeping ----- winding open.
Select one:
a. Both A & B
b. None of these
c. HV , LV
d. LV , HV
Feedback
The correct answer is: LV , HV
Question 5
13. The No Load primary current of 1 transformer is normally ---- of full load current
Select one:
a. 12 %
b. 15 %
c. 20 %
d. 2 to 5 %
Feedback
The correct answer is: 2 to 5 %
Question 6
14. In case of a transformer, the EMF induced in a secondary winding is due to
Select one:
a. None of these
b. Self induction
c. Both A and B
d. Mutual induction
Feedback
The correct answer is: Mutual induction
Question 7
15. Which of the following, is not a basic element of a transformer?
Select one:
a. Mutual flux
b. Primary winding
c. Secondary winding
d. Core
Feedback
The correct answer is: Mutual flux
Question 8
16. The hysteresis loss is proportional to ?
Select one:
a. Volume of magnetic material
b. Flux density
c. Frequency
d. All of these
Feedback
Question 9
17. In an ideal transformer :
Select one:
a. All of these
b. Core has no losses
c. Core has infinite permeability

d. Windings have no resistance
Feedback
Question 10
18. The eddy current loss is proportional to
Select one:
a. All of these
b. Flux density
c. Frequency
d. Thickness of material
Feedback
Question 11
19. The hysteresis loss is given by
Select one:
a. Ph = Kh. Bm1.6. f. V2 watt
b. Ph = Kh. B1.6. f. V watt
c. Ph = Kh. Bm1.6. f2. V watt

d. Ph = Kh. Bm1.6. f. V watt
Feedback
The correct answer is: Ph = Kh. Bm1.6. f. V watt
Question 12
2. In case of a transformer, the EMF induced in a primary winding is due to:
Select one:
a. None of these
b. Both A and B
c. Self induction
d. Mutual induction
Feedback
The correct answer is: Self induction
Question 13
20. Normally short circuit test is carried out on ---- winding, keeping ----- winding
shorted.
Select one:
a. Both A & B
b. HV , LV
c. None of these
d. LV , HV
Feedback
The correct answer is: HV , LV
Question 14
21. The main purpose of using core, in a transformer, is to
Select one:
a. Reduce hysteresis losses
b. Reduce iron losses

c. Reduce reluctance of magnetic circuit
d. Reduce eddy current losses
Feedback
The correct answer is: Reduce reluctance of magnetic circuit
Question 15
22. The rating of transformer is given in
Select one:
a. kVAR
b. kW
c. HP
d. kVA
Feedback
The correct answer is: kVA
Question 16
23. The hysteresis loss is minimized by
Select one:
a. Laminating the core
b. None of these
c. Selecting good quality of magnetic material
d. Both A & B
Feedback
The correct answer is: Selecting good quality of magnetic material
Question 17
Select one:
a. 250
b. 1250
c. 400
d. 1600
Feedback
Question 18
25. The condition for maximum efficiency is
Select one:
a. iron loss < copper loss
b. iron loss > copper loss
c. All of these
d. iron loss = copper loss
Feedback
The correct answer is: iron loss = copper loss
Question 19
26. The voltage regulation means
Select one:
a. Both A & C
b. Change in No Load voltage to full load voltage upon no load voltage
c. Change in Full Load voltage to No load voltage upon full load voltage
d. Change in No Load voltage to full load voltage upon full load voltage
Feedback
The correct answer is: Both A & C
Question 20
Select one:
a. There are 17 turns on primary and 1 turn on secondary
b. For every 17 turns on primary, there is 1 turn on secondary
c. Primary current is 17 times greater than the secondary current

d. Secondary voltage is 1/17th of primary voltage
Feedback
Question 21
28. The eddy current loss is given by
Select one:
a. Pe = Ke. Bm2. f2. t watt
b. Pe = Ke. Bm2. f. t2 watt
c. Pe = Ke. Bm1.6. f2. t2 watt

d. Pe = Ke. Bm2. f2. t2 watt
Feedback
The correct answer is: Pe = Ke. Bm2. f2. t2 watt
Question 22
secondary voltage of 400V, the number of secondary turns should be?
Select one:
a. 1600
b. 1250
c. 400
d. 2500
Feedback
Question 23
3. In case of a transformer, the primary & secondary windings are wound on a same
limb, so as to reduce ?
Select one:
a. Self induction
b. Mutual induction
c. None of these
d. Leakage reactance
Feedback
The correct answer is: Leakage reactance
Question 24
30. The rating of transformer is given in terms of
Select one:
a. True power
b. None of these
c. Reactive power
d. Apparent power
Feedback
The correct answer is: Apparent power
Question 25
31. The equivalent resistance (R1e) referred to primary side is
Select one:
a. R2 + (R2 . k 2)
b. R1 + (R2 . k 2)
c. R1 + (R2 / k 2)
d. R2 + (R1 / k 2)
Feedback
The correct answer is: R1 + (R2 / k 2)
Question 26
32.At No load , following losses are negligible
Select one:
b. Copper loss
c. Hysteresis loss
d. Iron loss
Feedback
Question 27
33. The transformation ratio (k) means
Select one:
a. I1/ I2
b. N2 / N1
c. V2 / V1
d. All of these
Feedback
Question 28
34. The copper saving in case of auto-transformer is
Select one:
a. k / weight of 2 winding transformer
b. Weight of 2 winding transformer / k

c. k x weight of 2 winding transformer
d. (1-k) x weight of 2 winding transformer
Feedback
The correct answer is: k x weight of 2 winding transformer
Question 29
35. The voltage regulation is positive for ------ load.
Select one:
a. Capacitive
b. Inductive
c. Both A & C
d. Resistive
Feedback
The correct answer is: Both A & C
Question 30
36. The eddy current loss is minimized by
Select one:
a. Laminating the core
b. Both A & B
c. Selecting good quality of magnetic material

d. None of these
Feedback
The correct answer is: Laminating the core
Question 31
Select one:
a. 250
b. 400
c. 1600
d. 900
Feedback
Question 32
38. The No Load primary current is the phasor sum of
Select one:
a. Magnetizing component of No Load current
b. Both A & B
c. None of these
d. Loss component of No Load current
Feedback
Question 33
39. The phenomenon of the self induction and mutual induction is felt, only when the
current in the coil is of ------ nature.
Select one:
a. DC
b. AC
c. None of above
d. Both of above
Feedback
The correct answer is: AC
Question 34
4. In case of which of the following equipment, the EMF induced is due to static
induction?
Select one:
a. DC motor
b. Transformer
c. DC generator
d. DC generator
Feedback
The correct answer is: Transformer
Question 35
40. The equivalent resistance (R2e) referred to secondary side is
Select one:
a. R2 + (R1 / k 2)
b. R2 + (R1 . k 2)
c. R1 + (R2 . k 2)
d. R1 + (R2 / k 2)
Feedback
The correct answer is: R2 + (R1 . k 2)
Question 36
41. An emf induced in a coil due to change in current, in a neighbouring coil is known as
Select one:
a. Rotating emf
b. Self induced emf

c. None
d. Mutually induced emf
Feedback
The correct answer is: Mutually induced emf
Question 37
42. The voltage ratio means
Select one:
a. V2 / V1
b. Both A & B
c. None of these
d. V1 / V2
Feedback
The correct answer is: V1 / V2
Question 38
43. An emf induced in a coil due to change in current in the same coil is known as
Select one:
a. Rotating emf
b. Self induced emf

c. Mutually induced emf
d. None
Feedback
The correct answer is: Self induced emf
Question 39
44. Before the point of maximum efficiency, ----- losses are more.
Select one:
a. Hysteresis loss & Eddy current loss
b. Both A & B
c. iron loss
d. Copper loss
Feedback
Question 40
45. The primary and secondary induced EMF's E1 and E2 in a two
Select one:
a. In phase with each other

b. Determined by nature of load on secondary
c. Anti-phase with each other
d. Equal in magnitude
Feedback
The correct answer is: In phase with each other
Question 41
46. Sandwich windings are used for ----- type of transformer.
Select one:
a. Shell
b. None of these
c. Core
d. Berry
Feedback
The correct answer is: Shell
Question 42
47. The voltage regulation is negative for ------ load.
Select one:
a. Capacitive
b. Resistive
c. Both A & C
d. Inductive
Feedback
The correct answer is: Capacitive
Question 43
48. The equivalent leakage reactance (X1e) referred to primary side is
Select one:
a. X2 + (X1 / k 2)
b. X1 + (X2 / k 2)
c. X1 + (X2 . k 2)
d. X2 + (X1 . k 2)
Feedback
The correct answer is: X1 + (X2 / k 2)
Question 44
49. In case of a transformer, the No Load power loss means
Select one:
b. Copper loss
c. Iron loss
d. Hysteresis loss
Feedback
The correct answer is: Iron loss
Question 45
5.Which of the following is /are the types of transformer ?
Select one:
a. All of these
b. Shell type
c. Core type
d. Berry type
Feedback
Question 46
50. A step up transformer increases
Select one:
a. Current
b. Voltage
c. Power
d. Frequency
Feedback
Question 47
51. Cylindrical windings are preferred for core type transformers as
Select one:
a. Easy for cooling
b. None of these
c. Easy for maintenance

d. Both A & B
Feedback
Question 48
52. ------- Losses are called as variable losses.
Select one:
a. Both A & B
b. Iron loss
c. Hysteresis loss + Eddy current loss

d. Copper loss
Feedback
Question 49
53. If the load current is halved, then copper losses will become
Select one:
a. Remain same
b. Half
c. Quarter
d. None of these
Feedback
The correct answer is: Quarter
Question 50
54. A step up transformer decreases
Select one:
a. Voltage
b. Current
c. Power
d. Frequency
Feedback
Question 51
55. The equivalent leakage reactance (X2e) referred to secondary side is
Select one:
a. X2 + (X1 . k 2)
b. X1 + (X2 . k 2)
c. X2 + (X1 / k 2)
d. X1 + (X2 / k 2)
Feedback
The correct answer is: X2 + (X1 . k 2)
Question 52
56. When will be the output of an AND gate is LOW ?
Select one:
a. When all inputs are HIGH
b. When all input is LOW
c. When any input is HIGH

d. When any input is LOW
Feedback
The correct answer is: When any input is LOW
Question 53
57. Cylindrical windings are used for ----- type of transformer.
Select one:
a. Core
b. Shell
c. None of these
d. Berry
Feedback
The correct answer is: Core
Question 54
58. Iron losses vary with -----, while copper losses vary with ------.
Select one:
a. Both A & B
b. Current , voltage
c. Voltage, current
d. None of these
Feedback
The correct answer is: Voltage, current
Question 55
59. If the load current is halved, then core losses will become
Select one:
a. Quarter
b. Half
c. None of these
d. Remain same
Feedback
The correct answer is: Remain same
Question 56
6. The losses obtained in Open Circuit Test are :
Select one:
a. Hysteresis losses
b. Eddy current losses
c. Both A & B
d. Copper losses
Feedback
Question 57
60. A step down transformer increases
Select one:
a. Voltage
b. Frequency
c. Current
d. Power
Feedback
Question 58
61. In case of phasor diagram of transformer, phasors for induced EMF's in primary and
secondary windings -------- flux.
Select one:
a. Out of phase with

b. In phase with
c. Lags behind by 900 with
d. None of these
Feedback
The correct answer is: Lags behind by 900 with
Question 59
62. The power factor is unity for purely ------ load.
Select one:
a. Capacitive
b. Inductive
c. Resistive
d. Both A & C
Feedback
The correct answer is: Resistive
Question 60
63. ------- Losses are called as constant losses.
Select one:
a. iron loss
b. Hysteresis loss + Eddy current loss
c. Both A & B
d. copper loss
Feedback
Question 61
64. The equivalent impedance (Z1e) referred to primary side is
Select one:
a. Z2 + (Z1 . k 2)
b. Z1 + (Z2 / k 2)
c. Z1 + (Z2 . k 2)
d. Z2 + (Z1 / k 2)
Feedback
The correct answer is: Z1 + (Z2 / k 2)
Question 62
65. According to Faraday's __________ Law, as long as there is change in flux, induced emf
persists.
Select one:
a. None
b. First
c. Third
d. Second
Feedback
The correct answer is: First
Question 63
66. In case of Core type of transformers, ---- surrounds ---- .
Select one:
a. Core , winding
b. None of these
c. Winding, core
d. Both A & B
Feedback
The correct answer is: Winding, core
Question 64
67. The condition for maximum efficiency is
Select one:
a. Both A & B
b. iron loss = copper loss
c. (Hysteresis loss + Eddy current loss ) = copper loss
d. iron loss < hysteresis loss

Feedback
Question 65
68. In case of Auto- transformer, which of the following is true , EXCEPT.
Select one:
a. Single winding
b. Constant output voltage
c. Single core
d. Less space required as compared to 2 winding transformer

Feedback
The correct answer is: Constant output voltage
Question 66
69. The primary and secondary windings of an ordinary transformer always have
Select one:
a. Same size of copper wire
b. Different number of turns
c. Common magnetic circuit

d. Different magnetic circuits
Feedback
The correct answer is: Common magnetic circuit
Question 67
7. The losses obtained in Short Circuit Test are .
Select one:
a. Eddy current losses
b. Copper losses
c. Hysteresis losses
d. Both A & B
Feedback
Question 68
70. A step down transformer decreases
Select one:
a. Voltage
b. Power
c. Current
d. Frequency
Feedback
Question 69
71. In case of 2 winding transformer, the EMF / turn in primary winding is always ---- the
EMF / turn in secondary winding.
Select one:
a. Greater than
b. Equal to
c. Equal to 1/k times

d. Equal to k times
Feedback
The correct answer is: Equal to
Question 70
72. Shell type of transformers use ---- windings.
Select one:
a. Cylindrical
b. None of these
c. Sandwich
d. Both A & B
Feedback
The correct answer is: Sandwich
Question 71
Select one:
a. For every 15 turns on primary, there is 1 turn on secondary
b. Primary current is 15 times greater than the secondary current

c. Secondary voltage is 1/15th of primary voltage
d. There are 15 turns on primary and 1 turn on secondary
Feedback
Question 72
74. Bushings are made with -----.
Select one:
a. Conducting Materials
b. Semiconducting materials
c. Insulating materials
d. Magnetic materials
Feedback
The correct answer is: Insulating materials
Question 73
75. In case of Shell type of transformers, ---- surrounds ---- .
Select one:
a. Winding, core
b. Both A & B
c. None
d. Core , winding
Feedback
The correct answer is: Core , winding
Question 74
76. After the point of maximum efficiency, ----- losses are more.
Select one:
a. Iron loss
b. Copper loss
c. Eddy current loss
d. Hysteresis loss
Feedback
Question 75
77. Core is made with -----.
Select one:
a. Magnetic materials
b. Semiconducting materials
c. Metals
d. Insulating materials
Feedback
The correct answer is: Magnetic materials
Question 76
78. Windings are made with -----.
Select one:
a. Magnetic materials
b. Conducting Materials
c. Semiconducting materials
d. Insulating materials
Feedback
The correct answer is: Conducting Materials
Question 77
79. The hysteresis loss is proportional to the following, EXCEPT
Select one:
a. Flux density
b. Thickness
c. Volume of magnetic material

d. Frequency
Feedback
The correct answer is: Thickness
Question 78
8. As load changes, ----- losses change accordingly.
Select one:
a. Hysteresis losses
b. Both A & B
c. Copper losses
d. Eddy current
Feedback
Question 79
80. Which of the following is / are type of winding in transformer ?
Select one:
a. Both A & B
b. Sandwich
c. Cylindrical
d. None of these
Feedback
Question 80
81. Windings are made with -----.
Select one:
a. Iron
b. Aluminium
c. Both A & B
d. Copper
Feedback
Question 81
82. Which of the following relation is true for transformer?
Select one:
a. V2 = E2 - I2Z2
b. E1 = V1 - I1Z1
c. E = 4.44 f Nm
d. All of these
Feedback
Question 82
Select one:
a. 250
b. 1000
c. 1600
d. 900
Feedback
Question 83
84. Which of the following relation is invalid for transformer?
Select one:
a. k = N2 / N1
b. E = 4.44 f Nm
c. V2 = E2 - I2Z2
d. E1 = V1 + I1Z1
Feedback
The correct answer is: k = N2 / N1
Question 84
85. In case of Auto-transformer, which is of the following is true?
Select one:
a. High efficiency as compared to 2 winding transformer
b. All the above

c. Less weight as compared to 2 winding transformer
d. Single winding only
Feedback
The correct answer is: All the above
Question 85
86. The copper loss is proportional to the following, EXCEPT
Select one:
a. Frequency
b. Flux density
c. Volume of magnetic material

d. Thickness
Feedback
The correct answer is: Volume of magnetic material
Question 86
87. Core is made with -----.
Select one:
a. Copper
b. Cobalt
c. Iron
d. Both A & B
Feedback
Question 87
9. The Open Circuit & Short Circuit Tests are carried out, so as to find.
Select one:
a. Efficiency
b. All of these
c. Regulation
d. Iron losses & Copper losses
Feedback

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((MARKS)) 1

((QUESTION)) If R1 is the primary winding resistance and R2 is the secondary winding

((OPTION_A)) R1+ R2/K2

((OPTION_B)) R2+ R1/K2

((OPTION_C)) R1+ K2R2

((OPTION_D)) R2+ K2R

((EXPLANATION When secondary resistantance transferred? to primary..It is divided by Suare of

((QUESTION)) The purpose of the transformer core is to provide ____________

((OPTION_A)) High reluctance path

((OPTION_B)) Low reluctance path

((OPTION_C)) High inductive path

((OPTION_D)) High capacitive path

((QUESTION)) Transformer core is designed to reduce ______________

((OPTION_A)) Hysteresis loss

((OPTION_B)) Eddy current loss

((OPTION_C)) Hysteresis loss and Eddy current loss

((OPTION_D)) Cannot be determined

((QUESTION)) Transformers windings are generally made of __________

((OPTION_D)) Steel iron alloy

((QUESTION)) Transformer ratings are given in _____________

((QUESTION)) Primary winding of a transformer ______________

((OPTION_A)) Is always a high voltage winding

((OPTION_B)) Is always a low voltage winding

((OPTION_C)) Could either be a low voltage or high voltage winding

((OPTION_D)) Cannot be determined

((EXPLANATION Primary winding used in a transformer, can be at higher or lower voltage

((QUESTION)) Sandwiched type of winding is used in ____________

((OPTION_A)) In all transformers

((OPTION_B)) In core type transformers

((OPTION_C)) In shell type transformers

((OPTION_D)) In all transformers except shell and core type transformers

((EXPLANATION According to the construction of transformers core type transformers don’t

((QUESTION)) A transformer cannot work on the DC supply because __________________

((OPTION_A)) There is no need to change the DC voltage

((OPTION_B)) A DC circuit has more losses

((OPTION_D)) Cannot be determined

((QUESTION)) Identify the correct statement relating to the ideal transformer.

((OPTION_A)) no losses and magnetic leakage

((OPTION_B)) a common core for its primary and secondary windings

((OPTION_C)) interleaved primary and secondary windings

((OPTION_D)) interleaved primary and secondary windings

((OPTION_A)) copper loss = iron loss

((OPTION_B)) copper loss < iron loss

((OPTION_C)) copper loss > iron loss

((OPTION_D)) cannot be determined

((QUESTION)) What is the no-load current drawn by transformer?

((OPTION_A)) 0.2 to 0.5 per cent

((OPTION_B)) 2 to 5 per cent

((OPTION_C)) 2 to 5 per cent

((OPTION_D)) 20 to 30 per cent

((QUESTION)) Purpose of no-load test on a transformer is ___________

((OPTION_A)) Copper loss

((OPTION_B)) Magnetising current

((OPTION_C)) Magnetising current and loss

((OPTION_D)) Efficiency of the transformer

((QUESTION)) Greater the secondary leakage flux ___________

((OPTION_A)) less will be the secondary induced emf

((OPTION_B)) less will be the primary induced emf