12 Physics Ip 2024 - 25

PHYSICS
INVESTIGATORY
PROJECT
2024-25
To Investigate the relation
between the ratio of output
voltage and input voltage of a
self designed transformer
Name :K.S. Adhitya Darssan
Class :XII – ‘A’
Batch :2024-25
DEPARTMENT OF PHYSICS
CERTIFICATE
This is to certify that adhitya of class
XII-A has successfully completed the
research on the mentioned topic under
the guidance of Mrs.Anand [physics
teacher] during the year 2024-25 in
partial fulfilment of pratical examination
SIGNATURE OF EXTERNAL EXAMINER SIGNATURE OF PHYSICS TEACHE R

INDEX
 ACKNOWLEDGEMENT
 AIM OF THE EXPERIMENT
 INTRODUCTION
 THEORY
 APPARATUS REQUIRED
 PROCEDURE
 PRECAUTIONS
 CONCLUSIONS
 BIBLOGRAPHY
ACKNOWLEDGEMENT
I would like to express my special thanks of

gratitude to my physics teacher Mr.Aanad as
well as our school principal Mrs.Silvie Nesa
who have gave the golden opportunity to do
this wonderful project on this topic “To
Investigate the relation between the ratio
of output voltage and input voltage of a
self designed transformer” which also
helped me in doing a lot of research work
and I came to know about so many things. I
am really thankful to them.
AIM OF THE
EXPERIMENT
To know The Investigate the relation

between the ratio of output voltage and input
voltage of a self designed transformer
INTODUCTION
It is 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.
A transformer is an electrical device
which is used for changing the A.C
voltages. A transformer is most widely
used device in both low and high current
circuit. Transformer is a device which
increase or decrease the voltage an
amazing strength of sizes. In electronic,
measurement and control circuit,
transformer size may be so small that it
weight only a few tens of grams where as
in high voltage power circuits, it may
weight hundred of tones.
A transformer which increase the
voltages is called a step up transformer.
A transformer which decrease the A.C
voltages is called a step down
transformer. An essential piece of a
apparatus both for high and low current
circuits.
THEORY
When an altering E.M.F is supplied to the
primary coil p1p2, an alternating current
starts falling in it. The altering current in the
primary produces a changing magnetic flux,
which induces altering voltage in the
primary as well as secondary. In a good
transformer whole of the magnetic flux ‍
linked with primary is also linked with
secondary, and then the induced E.M.F
induced in each turn of secondary is equal to
that induced in each turn of primary. Thus if
EP and ES be the instantaneous values of the
E.M.F’s induced in the primary and the
secondary and NP and NS are the no of
turns of the primary secondary coil of the
transformer and
d Φ/ d t ‍=rate of change of flux in each,
turnoff the coil at that instant
we have,
EP= -NP d Φ/ d t-(1) and
Es= -Ns d Φ/ d t-(2)
Since the above relations are true at
every instant, so by dividing 2 by 1,
we get,
ES/EP= -NS/NP-(3)
As EP is instantaneous value of back
E.M.F induced in the primary coil p1, so
the instantaneous current in primary coil
is due to the difference (E-EP) in the
instantaneous value of applied and back
E.M.F further if RP is the resistance o,
p1p2 coil, then the instantaneous
current IP in the primary coil is given by.
IP=E-EP/RP
E-EP = IP RP
RP>>>neglected so therefore
E-EP=0 or EP=E
Thus back E.M.F = input E.M.F
Hence equation 3 can be written as
ES/EP=ES/E= output E.M.F/input E.M.F
= NS/NP=K
Where k is constant, called turn or
transformation ratio
M
IN A STEP DOWN
TRANSFORMER
ES < E so K < 1, hence NS < NP

If IP = value of primary current at the
same instant
And,
IS = value of secondary current at
this same instant
then,
Input power at that instant = EP IP
and,
Output power at the same instant =
ES
Is
If there no losses of power in the
transformer
then,
input power = output power
or
EP IP = ES IS
or
ES/EP = IP/IS = K
IN A STEP UP
TRANSFORMER
ES > E so K > 1, hence NS > NP

As, K > 1, so IP > IS or IS < IP
i.e. current in secondary is weaker when

secondary voltage is higher
Hence, whatever we gain in voltage, we
lose in current in the same ratio.
Similarly it can be shown, that in a step

down transformer, whatever we lose in
voltage, we gain in current in the same
ratio.
Thus a step up transformer in reality

steps down the current & a step down
transformer steps up the current
APPARATUS REQUIRED
IRON ROD
COPPER WIRE
VOLTMETER
AMMETER
PROCEDURE
Take thick 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.
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.
Connect p1, p2 to A.C main and measure

the input voltage and current using A.C
voltmeter and ammeter respectively
Similarly measure the output voltage and
current through s1and s2
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

transformer by changing number of turns
in primary and secondary coil
PRECAUTION
CONCLUSION
The output voltage of the transformers
across the secondary coils depends upon
the ratio (NS//NP) with respect to input
voltage
There is a loss of power between input

and output coil of a transformers
BIBLOGRAPHY
Ncert Textbook
Physics Lab Mannual
www .wikipedia.com

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PHYSICS

SIGNATURE OF EXTERNAL EXAMINER SIGNATURE OF PHYSICS TEACHE R

I would like to express my special thanks of

To know The Investigate the relation

ES < E so K < 1, hence NS < NP

ES > E so K > 1, hence NS > NP

i.e. current in secondary is weaker when

Similarly it can be shown, that in a step

Thus a step up transformer in reality

Take thick rod and cover it with a thick

Cover the primary coil with a sheet of

Connect p1, p2 to A.C main and measure

Now connect s1 and s2 to A.C main and

Repeat all steps for other self made

There is a loss of power between input

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