The document is a project report by Ruchi Dhakad from Kendriya Vidyalaya No. 1 Indore, focused on investigating the relationship between input and output voltages, and the number of turns in the primary and secondary coils of transformers. It includes an introduction to transformers, types, theoretical underpinnings, practical procedures for constructing step-up and step-down transformers, and various applications of transformers. The report also acknowledges the guidance received from the physics teacher and outlines the project structure with an aim, methodology, and bibliography.

1. PM SHRI KENDRIYA VIDYALAYA NO.1 INDORE
PHYSICS
investigatory project
report 2024-25
Transformer
To Investigate the relation between the ratio of input and
output voltages,Number if turns in the primary and
secondary coil of a Transformer .
SUBMITTED TO:
Mr. Deepak Dubey
PGT(PHYSICS )
KV NO.1 INDORE
SUBMITTED BY:
Ruchi Dhakad
CLASS XII B
KV NO.1 INDORE

2. ACKNOWLEDGEMENT
I would like to express my gratitude
to my Physics teacher Mr. DEEPAK
DUBEY for the guidance and support
throughout this project.I would also
like to thank my school for providing
necessary resources and laboratory
equipment.Lastly my sincere thanks
to my friends and family for their
constant encouragement.

3. CERTIFICATE
This is to certify that Ms.RUCHI
DHAKAD of class XII of KENDRIYA
VIDYALAYA No.1 INDORE has
successfully completed the
investigatory project in PHYSICS On the
topic “To investigate the relation
between the ratio of input and output
voltages ,Number of turns in the
primary and secondary coil of a
Transformer ”under the guidance of
Physics teacher Mr.DEEPAK DUBEY as
prescribed by the Central Board of
Secondary Education during the year
2024-25

4. INDEX
•Aim
•Introduction
•Types of Transformers
•Theory and Mathematical
derivations
•Simple circuit Diagram
•Circuit Diagrams for Step-
up and Step-Down
Transformers
•Uses of Transformers
•Bibliography

5. AIM
To investigate the relation
between the ratio of:
1. Input and Output
voltage
2. Number of turnings in
the secondary coil and
primary coil of a self
made transformer.

6. INTRODUCTION
The transformer is a device used
for converting a low voltage to a
high alternating voltage or vice-
versa.
A transformer is based on the
principle of mutual Induction
according to this principle ,the
amount of magnetic flux linked
with a coil changing, an emf 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
high and low current circuit . As
such transformers are built in
amazing strength of sizes.

7. Types of
TRANSFORMERS
•STEP UP TRANSFORMER:
For a step up transformer the number of
turns in the secondary will be greater
than that in the primary( 𝐍𝐬 > 𝐍𝐏). Thus
for a step up transformer secondary
voltage will be greater than primary
voltage,but the secondary current will be
less than primary current.
Vs=(Ns/Np)Vp
Ns/Np>1
Vs>Vp
Is=(Np/Ns)Vp
Np/Ns<1
Is<Ip

8. STEP DOWN TRANSFORMER:
• For a step down transformer the number
of turns in the secondary will be less
than that in the primary( 𝐍𝐬 ˂ 𝐍𝐏).Thus
for a step up transformer secondary
voltage will be less than primary voltage,
but the secondary current will be greater
than primary
Vs=(Ns/Np)Vp
Ns/Np<1
Vs<Vp
Is=(Np/Ns)Vp
Np/Ns>1
Is>Ip

9. THEORY AND
MATHEMATICAL
DERIVATIONS
• When our altering EMF is supplied to
the primary coil p1p2, an altering
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 EMF induced in each turn of
the secondary is equal to that in each
of the primary. Thus, if Ep and Es be
the instantaneous values of the EMF
induced in the primary and secondary
and Np and Ns are the number of
turns of the primary secondary coils of
the transformer and dΦ/dt= rate of
change of flux in each turnoff the coil
at this instant, we have:
Ep = - Np dΦ/dt--------------(1) and
Es = - Ns dΦ/dt---------------(2)

10. 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 coil is given by :
Ip=E-Ep/Rp
E-Ep=IpRp
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 on
transformation ratio.

11. CIRCUIT DIAGRAM
FOR STEP UP TRANSFORMER:
• Working:In a step-down transformer,
There are many turns on the secondary
winding than in the primary winding in
the step-up transformers. Thus, the
voltage supplied in the secondary
transformer is greater than the one
supplied across the primary winding.
Because of the principle of conservation
of energy, the transformer converts low
voltage, high-current to high voltage-low
current. In other words, the voltage has
been stepped up.
• You can find step-up transformers
located near power plants that are
designed to operate megawatts of
power. Apart from the power plants,
step-up transformers can also be used
for local and smaller applications such as
x-ray machine which requires about
50,000 volts to work. Even a micro-wave
oven requires a small step-up
transformer to operate.

12. FOR STEP DOWN
TRANSFORMER:
• In a step-down transformer is one who
secondary windings are fewer than the
primary windings. In other words, the
transformer's secondary voltage is less
than the primary voltage. So, the
transformer is designed to convert high-
voltage, low- current power into a low-
voltage, high current power and it is
mainly used in domestic consumption.
• A common case of step-down
application is in the case of door bells.
Normally, door bells use 16 volts, but
most household power circuits carry
110-120 volts. Therefore, the doorbell's
step-down transformer receives the 110
volts and reduces it to lower voltage
before supplying it to the doorbell.
• Step-down transformers are mostly used
to convert the 220 volts electricity to the
110 volts required in most domestic
equipment.

13. For STEP UP TRANSFORMER

14. FOR STEP DOWN
TRANSFORMER

15. APPARATUS REQUIRED:
•Iron Rod
•Copper Wire
•Hot Wire Ammeter
•Hot Wire Voltmeter
Procedure:
•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.
•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.
•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 sland s2.
•Now connect sland s2to 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.

16. Apparatus:

17. USES OF TRANSFORMERS
•In voltage regulator for T.V.,
refrigerator, computer, air conditioner,
etc.
•A step down transformer is used for
welding purposes.
•A step down transformer is used for
obtaining large current.
•A Step up transformer is used for
production of X-Rays and NEON
advertisements .
•Transformers are used in voltage
regulators and stabilized power
supplies.
•Transformers are used in the
transmissions of a.c. over long
distances.
• Small transformers are used in Radio
sets, telephones , loud speakers etc

18. BIBILOGRAPHY
• www.google.com
• Physics NCERT
• Hsslive.IN