IND

EX
 Aim of the Project
 Introduction
 Working Principle of a Transformer
 Theory
 Materials required
 Procedure Followed
 Observations
 Applications of Transformer
 Conclusions
 AIM OF THE PROJECT

To investigate relation between the

ratio of:
 Output and input voltage and
 Number of turns in the
secondary coil and primary coil of a
self-designed transformer.
 INTRODUCTION
The transformer is a device used for converting a low alternating voltage to a high
alternating voltage or a high alternating voltage into a low alternating voltage. It is
a static electrical device that transfers energy by inductive coupling between its
winding circuits. Transformers range in size from a thumbnail-sized coupling
transformer hidden inside a stage microphone to huge units weighing hundreds of
tons used in power plant substations or to interconnect portions of the power
grid. All operate on the same basic principles, although the range of designs is
wide. While new technologies have eliminated the need for transformers in some
electronic circuits, transformers are still found in many electronic devices.
Transformers are essential for high-voltage electric power transmission, which
makes long-distance transmission economically practical. A transformer is most
widely used device in both low and high current circuit. In a transformer, the
electrical energy transfer from one circuit to another circuit takes place without
the use of moving parts. A transformer which increases the voltages is called a
step-up transformer. A transformer which decreases the A.C. voltages is called a
step-down transformer. Transformer is, therefore, an essential piece of apparatus
both for high and low current circuits.

Working Principle
The electric transformer works on the fundamental principle of electromagnetic
induction, a concept first discovered by Michael Faraday in the 19th century. The
transformer consists of two coils of wire, known as the primary and secondary
windings, which are usually wound around a common magnetic core. When an
alternating current (AC) flows through the primary winding, it generates a
changing magnetic field around the coil. According to Faraday’s law of
electromagnetic induction, this changing magnetic field induces an
electromotive force (EMF) or voltage in the secondary winding. The key
principle here is that the transformer relies on the mutual induction between the
primary and secondary windings through the magnetic flux linkage.
 THEORY
.

Construction
A transformer consists of a rectangular shaft iron core made of
laminated sheets, well insulated from one another. Two coils N P
and NS are wound on the same core, but are well insulated with
each other. Note that the both the coils are insulated from the
core, the source of alternating e.m.f is connected to the
primary coil and a load resistance R is connected to the
secondary coil through an open switch S. Thus there can be no
current through the secondary coil so long as the switch is
open. For an ideal transformer, we assume that the resistance
of the primary and secondary winding is negligible. Further, the
energy loses due to magnetic the iron core is also negligible.
For operation at low frequency, we may have a soft iron. The
soft iron core is insulating by joining thin iron strips coated with
varnish to insulate them to reduce energy losses by eddy
currents. The input circuit is called primary and the output
circuit is called secondary.
 Working of Transformer
A Transformer based on the principle of mutual induction.
According to this principle, the amount of magnetic flux linked
with a coil changing, an e.m.f is induced in the neighbouring
coil that is if a varying current is set-up in a circuit induced
e.m.f. is produced in the neighbouring circuit. The varying
current in a circuit produce varying magnetic flux which induces
e.m.f. in the neighbouring circuit.

The transformer consists of two coils. They are insulated with

each other by insulated material and wound on a common core.
For operation at low frequency, we may have a soft iron. The
soft iron core is insulating by joining thin iron strips coated with
varnish to insulate them to reduce energy losses by eddy
currents. The input circuit is called primary and the output
circuit is called secondary.
 MATERIAL REQUIRED

 Iron Rod

 Voltmeter

 Ammeter

 Copper Wire
 PROCEDURE FOLLOWED
1. Take thick iron rod and cover it with a thick paper and
wind a large number of turns of thin Cu wire on thick
paper (say 60). This constitutes primary coil of the
transformer.
2. Cover the primary coil with a sheet of paper and wound
relatively smaller number of turns (say 20) of thick copper
wire on it. This constitutes the secondary coil. It is a step-
down transformer.
3. Cover the primary coil with a sheet of paper and wound
relatively smaller number of turns (say 20) of thick copper
wire on it. This constitutes the secondary coil. It is a step-
down transformer.
4. Similarly, measure the output voltage and current through
s1 and s2
5. Now connect s1 and s2 to A.C main and again measure
voltage and current through primary and secondary coil of
step-up transformer.
Repeat all steps for other self-made transformers by changing
number of turns in primary and secondary coil.
 OBSERVATION
1. We will find that ratio of and across the two coils is equal
to the ratio of number of turns in the coil P to that in the
coil S. i.e., Vp/Vs = Np/Ns
2. The coil P (to which AC voltage is applied) is called the
primary and coil S (in which AC is induced) is called the
secondary.
3. Since coil S is placed very close to the coil P, the power in
the primary is transferred into the secondary through
mutual induction.
4. It is clear from equation 1, that by appropriate choice of
the turn ratio i.e., Np/Ns, we can obtain a higher voltage or
lower voltage in S compared to that in P.

Energy Loss
In practice, the output energy of a transformer is always less
than the input energy, because energy losses occur due to a
number of reasons as explained below.
 Loss of Magnetic Flux: The coupling between the coils is
seldom perfect. So, whole of the magnetic flux produced
by the primary coil is not linked up with the secondary
coil.
 Iron Loss: In actual iron cores in spite of lamination, Eddy
currents are produced. The magnitude of eddy current
may, however be small. And a part of energy is lost as the
heat produced in the iron core.
 Copper Loss: In practice, the coils of the transformer
possess resistance. So, a part of the energy is lost due to
the heat produced in the resistance of the coil.
  Hysteresis Loss: The alternating current in the coil tapes
the iron core through complete cycle of magnetization. So,
Energy is lost due to hysteresis.
 Magneto restriction: The alternating current in the
Transformer may be set its parts in to vibrations and
sound may be produced. It is called humming. Thus, a part
of energy may be lost due to humming.

APPLICATION OF
TRANSFORMER
1. Electric Power Transmission: Transformers are crucial in
power transmission networks to step up voltage for
efficient long-distance transmission and step-down voltage
for distribution to end-users.
2. Voltage Regulation: Transformers help maintain a stable
voltage level by adjusting the voltage as needed, ensuring
consistent and reliable electrical supply.
3. Power Distribution: They are used in power distribution
systems to provide various voltage levels suitable for
residential, commercial, and industrial applications.
4. Power Supply Units: Transformers are employed in power
supply units of electronic devices, converting AC power
from outlets to the DC power needed by devices like
computers and chargers.
5. Voltage Transformation: Transformers change the voltage
levels, allowing electricity to be transmitted at high
voltages to reduce energy losses and then be distributed
at lower voltages for use.
6. Industrial Applications: Transformers power various
industrial machinery and equipment by adapting electrical
voltage to meet specific operational requirements.
7. Electrical Appliances: Many electronic devices and
appliances use transformers to convert electricity to the
required voltage for their operation.
 CONCLUSIONS
 The output voltage of the transformer across the
secondary coil depends upon the ratio (Ns/Np) with
respect to the input voltage.
 The output voltage of the transformer across the
secondary coil depends upon the ratio (Ns/N p) with
respect to the input voltage.
 There is a loss of power between input and output coil
of a transformer.
 BIBLIOGRAPHY

 Physics Part-II, Textbook for Class XII, National

Council of Educational Research and Training, New
Delhi.
 New Simplified Physcs by S.L. Arora, A Reference
Book For Class XII, Dhanpat Rai & Co. (Pvt.) Ltd.,
Educational & Technical Publishers.
 Lab Manual of Physics by S. L. Arora for Class XII,
Dhanpat Rai & Co. (Pvt.) Ltd., Educational &
Technical Publishers.
 https://www.slideshare.net/slideshow/
transformerclass-12-investigatory-project/
40992810
 https://www.scribd.com/document/242804463/
Project-on-Transformers-Class-XII
 https://www.studocu.com/in/document/dav-senior-
secondary-public-school/physics-class-xii/12-
physics-project-transformer/67560255
 https://knowledgecycle.in/transformer-
investigatory-project-pdf-class-12/
 https://in.pinterest.com/pin/982558843690088278/
 Internet