DAV PUBLIC SCHOOL POKHARIPUT

INVESTIGATORY PROJECT OF PHYSICS

ON

For the partial fulfilment of the conditions laid down for

AISSCE 2022-23
SUBMITTED BY :-

NAME: TAMANNA PRIYADARSHINI

CLASS: XII/D2

ROLL NO. :

UNDER THE GUIDANCE

MRS DURGESH NANDINI SAMAL

PGT PHYSICS
I would like to profound sense of gratitude to my guide Mrs
Durgesh nandini mam my physics teacher for her valuable
guidance and suggestions during preparation of my project
work.
I am grateful to my principal Ms Sujata for her
encouragement and constant inspiration.
With great pleasure I extend my gratitude to my parents and
other family members and friends for their support which
enable me to complete my work successfully.

Date:-
I tamannapriyadarshini, a student of class XII, sec-D2 of
DAV public school pokhaariput hereby submit the project
entitiled TRANSFORMER for the physics partial fulfilment
of the conditions laid down for AISSCE 2022-23 . This project
consist of orginal work done by me under the able guidance
and supervision of my physics teacher.

Signature of student
This is to clarify that the project entitiled “TRANSFORMER” is
an original piece of work by tamanna priyadarshini of class XII
sec D2 is in accordance with the topic allotted to her.
This project is submitted towards the partial fulfilment of the
conditions laid down for AISSCE 2022-23 and embodies the work
done by her in my guidance and supervision.

Signature of external supervisor

Signature of internal supervisior

Signature supervisior
INTRODUCTION
THEORY AND WORKING OF TRANSFORMER
STEP UP TRANSFORMER
STEP DOWN TRANSFORMER
EFFICENCY
ENERGY LOSS
CONCLUSION
BIBLIOGRAPHY
To investigate the relation between the ratio

1. Input and output voltage.

2. Number of turnings in the secondary coil and

primary coil of a self made transformer.
The transformer is a device used for converting a low
alternating voltage to a high alternating voltage or vice-versa.

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 neighboring
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. As such transformers are
built in an amazing strength of sizes. In electronic,
measurement and control circuits, 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.

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.
When an altering e.m.f. is supplied to the primary coll 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 in the secondary. In a
good-transformer, whole of the magnetic flux linked with primary
is also linked with the secondary, and then the induced e.m.f.
induced in each turn of the secondary is equal to that induced in
each turn of the 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 coils of
the transformer and

do/dt = rate of change of flux in

each turnoff the coil at this instant, we have

Ep=-Np dop/dt, (1)

and

Es-Ns dep/dt (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 the 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 values of the
applied and back.

e.m.f. further if Rp is the resistance o, p1p2 coil, then the

instantaneous current Ip in the primary coll is given by

IP = E - E p / R p

E - Ep =Ip Rp

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.

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 instant, then

Input power at the instant = Ep Ip

And

Output power at the same instant = Es Is

If there are no losses of power in the transformer, then

Input power output power

Or

Ep / p = Es / s

Or

Es / E p = lp / I s = K

Es > E so K > 1 hence Ns > NpAs k > 1 so Ip >/s or Is
< 10 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.
 1. NCERT TEXT BOOK
2. INTERNET
3. PHYSICS LAB MANUEL
4. GOOGLE
5. SCRIBIDD
1. The output voltage of the transformer across the
secondary coil depends upon the ratio (Ns/Np) with respect
to the input voltage

2. The output voltage of the transformer across the

secondary

coil depends upon the ratio (Ns/N p) with respect to the

input

voltage

3. There is a loss of power between input and output coil of

a transformer.
 1. Keep safe yourself from high voltage.

2. While taking the readings of current and voltage the

A.C should remain constant

1. Values of current can be changed due to heating effect.

2. Eddy current can change the readings.

1. In voltage regulator for T.V., refrigerator, computer, air
conditioner, etc.

2. A step down transformer is used for welding purposes.

3. A step down transformer is used for obtaining large

current.

4. A step up transformer is used for the production of X-

Rays and NEON advertisement.

5. Transformers are used in voltage regulators and

stabilized

power supplies.

6. Transformers are used in the transmissions of a.c. over

long

distances.

7. Small transformers are used in Radio sets, telephones,

loud speakers and electric bells etc
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. Connect p1, p2 to A.C main and measure the input

voltage and current using A.C voltmeter and ammeter
respectively.

4. Similarly, measure the output voltage and current

through sland $2.

5. Now connect sland $2to AC main and again measure

voltage and current through primary and secondary coil of
step up transformer.

6. Repeat all steps for other self made transformers by

changing number of turns in primary and secondary coil.
Efficiency of a transformer is defined as the ratio of output
power to the input power. L.e.

n = output power / input power = Es Is/Ep lp

Thus in an ideal transformer, where there is no power losses

n=1
But in actual practice, there are many power losses;
therefore the efficiency of transformer is less than one.
Following are the major sources of energy loss in a
transformer:

1. Copper loss is the energy loss in the form of heat in the

copper coils of a transformer. This is due to joule heating of
conducting wires.

2. Iron loss is the energy loss in the form of heat in the iron
core of the transformer. This is due to formation of eddy
currents in iron core. It is minimized by taking laminated
cores.

3. Leakage of magnetic flux occurs inspite of best

insulations. Therefore, rate of change of magnetic flux
linked with each turn of 5152 is less than the rate of change
of magnetic flux linked with each turn of P1P2.

4. Hysteresis loss is the loss of energy due to repeated

magnetization and demagnetization of the iron core when
A.C. is fed to it.

5. Magneto striation i.e. humming noise of a transformer

 Ammeter

copper wire

voltmeter

iron rod