The document is a physics project report submitted by Anup Kumar Sen on transformers. It begins by thanking various people who supported the project. It then includes a certification that the project was supervised and the results were checked. The project covers the introduction, principle, construction, theory and working, efficiency, and energy losses of transformers in 14 sections with citations. It aims to provide an overview of transformers for an exam.

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INVESTIGATORY PROJECT ON PHYSICS
FOR AISSCE 2019-20
TOTIC:-
Submitted by:-
-ANUP KUMAR SEN
(XII -Science)
AISSCE Roll no._________

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I would like to express my greatest gratitude to the people who have helped
& Supportedme throughout my project. I respect and thanks to Mr.N C Kar
Principal of JNV ,Sarang Dhenkanal and I am grateful to my physics teacher,
Mr. M .KSahoofor his continuous support for the project, from initial advice &
I wish to thank my parents for their undivided support and interest who
inspired me and encouraged me to go my own way, without whom I would be unable
to complete my project.
A special thank of mine goes to my best friend who helped me in completing
the project & he exchanged his interesting ideas, thoughts & made this project easy
and accurate.
At last but not the least I want to thank my friends who appreciated me for my
work and motivated me and finally to God who made all the things possible.
-ANUP KUMAR SEN

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This is to certify that the project on “Transformer”
submitted by“ANUP KUMAR SEN”of class 12th
Science is a pursue
and sincere work of his intelligence and deep study of the topic.
He has been working under my supervision during the Session2019-20.
The material involved in his report is entirely his contribution.
The results are satisfactory and has been checked by me.
.
Date:_________________________________
------------------------------------------------------ -----------------------------------------------------------
(Principal) (subjectteacher)
Mr. N. C Kar Mr. M.K. Sahoo

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 INTRODUCTION
PRINCIPLE
CONSTRUCTION
 THEORY AND WORKING
 EFFICIENCY
ENERGY LOSSES

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Atransformerisanelectricaldevicewhichisusedforchangingthe
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 hundredof 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.
INTRODUCTION

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It is based on the principle of mutual induction that is if a varying current is
set-up in a circuit then induced e.m.f. is produced in the neighboring circuit.
The varying current in a circuit produce varying magnetic flux which
inducese.m.f. in the neighboringcircuit.
Principle

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A transformer consists of a rectangular shaft iron core made of laminated
sheets, well insulated from one another. Two coils p1& p2 and s1& s2 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
p1p2, the primary coil and a load resistance R is connected to s1 s2, the secondary
coil through an open switch S. thus there can be no current through the sec. coil
so long as the switch is open.
For an ideal transformer, we assume that the resistance of the primary &
secondary winding is negligible. Further, the energy loses due to magnetic the
iron core is also negligible.
An ideal voltage step-down transformer. The secondary current arises from the
action of the secondary EMF on the (not shown) load impedance.
Construction

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History of transformer
Electromagnetic induction, the principle of the operation of the transformer,
Was discovered independently by Michael Faraday in (1831), Joseph Henry
in(1832), and others. The relationship between EMF and magnetic flux is an
equation now known as Faraday's law ofinduction:
|ᵋ| = |d ΦB /dt|
where |ᵋ| is the magnitude of the EMF in Volts and ΦBis the magnetic flux
through the circuit inwebers
.FIRST ALTERNATING CURRENT TRANSFORMERS:-
By the 1870s, efficient generators producing alternating current (AC) were
available, and it was found AC could power an induction coil directly, without
an interrupter.
In 1876, Russian engineer PavelYablochkovinvented a lighting system
based on a set of induction coils where the primary windings were connected to
a source of AC. The secondary windings could be connected to several 'electric
candles' (arc lamps) of his own design. The coils Yablochkov employed
functioned essentially as transformers.

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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 in the secondary. In a good-transformer, whole of
the magnetic flux linked with primary is also linked with the secondary,
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 transformerandDфь / dt = rate of change of flux in each
Turnoff the coil at this instant, we have
Ep = -Npdфь/dt ---1
Es =-Nsdфь/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
Theory and Working of
Transformer

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current Ip in the primary coil is given by
Ip= E – Ep / Rp
E – Ep = IpRp
When the resistance of the primary is small, RPIP can be negiected
Therefore ,E – Ep= 0 or Ep =E
Thus; back e.m.f =inpute.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.
IN A STEP UP TRANSFORMER:
Es> E so K > 1
hence Ns> Np
IN A STEP DOWN TRANSFORMER:
Es< E so K < 1
hence Ns< Np
Ip= value of primary current at the same instant
And, Is= value of sec. current at this instant,
then Input power at the instant = EpIp and
Output power at the same instant = EsIs
If there are no losses of power in the transformer, then
Input power = output power

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EPIP = Es Is
Es/Ep = Ip / Is = K
IN A STEP UP TRANSFORMER:
As k> 1, so Ip> Is or Is<Ip
i.e. current in sec. is weaker when secondary voltage is higher.
Hence, whatever we gain in voltage, we lose in current in the
sameratio.
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.

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Efficiency
Efficiency of a transformer is defined as the ratio of output
power to the input power. i.e.
η = output power / inputpower
= Es Is / EpIp
Thus in an ideal transformer, where there is no power losses,
η = 1. But in actual practice, there are many power losses,
therefore the efficiency of transformer is less than one.

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Energy losses
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
conductingwires.
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
laminatedcores.
3. Leakage of magnetic flux occurs inspite of best insulations.
Therefore, rate of change of magnetic flux linked with each
turn of S1S2 is less than the rate of change of magnetic flux
linked with each turn ofP1P2.
4. Hysteretic loss is the loss of energy due to repeated
magnetization and demagnetization of the iron core when
A.C. is fed toit.
5. Magneto striation i.e. humming noise of atransformer.

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Bibliography
 www.google.co.in/
 www.slideshare.com/
 www.en.wikipedia.com/
 NCERT Textbook ofPhysics
 Physics LaboratoryManual