ACKNOWLEDGEMENT I would like to express my special thanks of gratitude to my Physics teacher, Mr.Sujanapal as well as our Principal Mr.S.S.U.Tare! who ga"e me this opportunity to do this project on the topic #$lack %ole Thermodynamics&. Thermodynamics&. It helped me in doing a lot of research and through it I came to know aout so many new things. I am really thankful to them. Secondly I would lik li ke to thank my parents parents and friends who helped me a lot in 'nishing this project within the limited time. I would also like to thank the ($S) oard for gi"ing me this opportunity to explore eyond the regular *()+T textook.
INDEX .
Intr Intro oduc ducti tion on.... .... .... .... .... ...... ....... .... ....... .... ..
......page . /j /jecti ecti" "e... e........ .... ....... .... ...... ...... ...... ....... .... .. ......... page 0 -. Theo Theory ry.. .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... ........ page 1 2. 3p 3ppa para ratu tus s.. .... .... ....... .... ...... ...... ...... ....... .... ..... .....page 0. (ircuit 4iagram.......................page 1. Procedu cedurre.. e..... ....... .... .... .... .... ...... ....... .... ....... ....page 2
5.
Uses......................................
........ page 0 6. (onclusion............................ .....page 1 7. $iliography.......................... ...page 6
INTRODUCTION The transformer is a de"ice used for con"erting a low alternating "oltage to a high alternating "oltage or "ice8"ersa. 3 Transformer ased on the Principle of mutual induction according to this principle, the amount of magnetic 9ux linked with a coil changing, an e.m.f is induced in the neighoring coil. 3 transformer is an electrical de"ice which is used for changing the 3.(. "oltages. -
3s such transformers are uilt in an ama!ing strength of si!es. In electronic, measurement and control circuits, transformer si!e may e so small that it weight only a few tens of grams where as in high "oltage power circuits, it may weight hundreds of tones.
In a transformer, the electrical energy transfer from one circuit to another circuit takes place without the use of mo"ing parts. 3 transformer which increases the "oltages is called a step up transformer. 3 transformer which decreases the 3.(. "oltages is called a step8down transformer. Transformer is, therefore, an essential piece of apparatus oth for high and low current circuits.
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OBJECTIVE To investigate the reation !et"een the ratio o#$ . Input and output "oltage. . *umer of turnings in the secondary coil and primary coil of a self8made transformer.
0
T%EOR& :hen an altering e.m.f. is supplied to the primary coil pp, an alternating current starts falling in it. The altering current in the primary produces a changing magnetic 9ux, which induces altering "oltage in the primary as well as in the secondary. In a 1
good transformer, whole of the magnetic 9ux linked with primary is also linked with the secondary, and then the induced e.m.f. induced in each turn of the secondary is e;ual to that induced in each turn of the primary. Thus if )p and )s e the instantaneous "alues of the e.m.f.&s induced in the primary and the secondary and *p and *s are the no. of turns of the primary secondary coils of the transformer and< dф / dt = rate of change of ux in each turno the coil at this instant, we have Ep = -Np dф/dt _______________ (! "nd Es = -Ns dф/dt
_______________
(#!
Since the ao"e relations are true at e"ery instant, so y di"iding y , we get< Es / Ep = - Ns / Np ______________
($!
3s )p is the instantaneous "alue of ack e.m.f induced in the primary coil p, so the instantaneous current in primary coil is due to the di=erence >) ? )p @ in the 5
instantaneous "alues of the applied and ack e.m.f. further if +p is the resistance o, pp coil, then the instantaneous current Ip in the primary coil is gi"en y< %p
= E & Ep / 'p E & Ep = %p 'p
:hen the resistance of the primary is small, +p Ip can e neglected so therefore< E & Ep = or Ep = E )hus *ac+ ef = input ef
%ence e;uation - can e written as< Es / Ep = Es / E = output ef / input ef = Ns / Np = .
6
:here A is constant, called turn or transformation ratio.
IN A 'TE()U( TRAN'*ORMER$
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)s B ) so A B , hence *s B *p 3s, k B , so Ip B Is or Is C Ip i.e. current in secondary is weaker when secondary "oltage is higher. %ence, whate"er we gain in "oltage, we lose in current in the same ratio. Similarly it can e shown, that in a step down transformer, whate"er we lose in "oltage, we gain in current in the same ratio. Thus a step up transformer in reality steps down the current D a step down transformer steps up the current.
E
IN A 'TE()DOWN TRAN'*ORMER$
)s C ) so A C , hence *s C *p If
Ip F "alue of primary current at the same instant
3nd
Is F "alue of secondary current at this instant, then
Input power at the instant F
)p Ip
/utput power at the same instant F
and )s Is
If there are no losses of power in the transformer, then< Input power F output power
/r
)p Ip F
)s Is /r
)s G )p
F
Ip G Is F A
A++arat,s re-,ire. •
Iron +od<
•
(opper :ire<
•
Holtmeter<
•
3mmeter<
-
CIRCUIT DIAGRAM
2
(ROCEDURE Take
thick iron rod and co"er it with a thick paper and wind a large numer of turns of thin (u wire on thick paper >say 0
1E@. This constitutes primary coil of the transformer. (o"er the primary coil with a sheet of paper and wound relati"ely smaller numer of turns >say E@ of thick copper wire on it. This constitutes the secondary coil. It is a step down transformer. (onnect p, p to 3.( main and measure the input "oltage and current using 3.( "oltmeter and ammeter respecti"ely. Similarly, measure the output "oltage and current through sand s. *ow connect sand sto 3.( main and again measure "oltage and current through primary and secondary coil of step up transformer. +epeat all steps for other self8made transformers y changing numer of turns in primary and secondary coil.
U'E' O* TRAN'*ORMER 3 transformer is used in almost all a.c. operations< 1
In "oltage regulator for T.H., refrigerator, computer, air conditioner, etc. 3 step down transformer is used for welding purposes. 3 step down transformer is used for otaining large current. 3 step up transformer is used for the production of 8+ays and *)/* ad"ertisement. Transformers are used in "oltage regulators and staili!ed power supplies. Transformers are used in the transmissions of a.c. o"er long distances. Small transformers are used in +adio sets, telephones, loud speakers and electric ells etc.
'OURCE' O* ERROR 5
Halues of current can e changed due to heating e=ect. )ddy current can change the readings.
CONCLU'ION The
output "oltage of the transformer across the secondary coil depends upon the ratio >*sG*p@ with respect to the input "oltage The output "oltage of the transformer across the secondary coil depends upon the ratio >*sG* p@ with respect to the input "oltage There is a loss of power etween input and output coil of a transformer.
(RECAUTION' 6
Aeep safe yourself from high "oltage. :hile taking the readings of current and "oltage the 3.( should remain constant.
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BIBLIOGRA(%&
%)JP K+/M I*T)+*)T I*K/+M3TI/* K+/M JI$+3+L %)JP K+/M T)3(%)+S *()+T textook class *()+T physics la Manuel
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