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Diagram A

ASCT/EEE/LAB/BEE-10

(Thevenins Theorem)

EXPERIMENT NO. 10

AIM: To Verify Thevenins Theorem

INSTRUMENTS REUIRE!:

S. No. Instruments Range Qty

1. Regulated o!er Su""l# 0-$0% 1

&' Ammeter (C) 0-A 1

$' %oltmeter (C) 0-$0% &

*' Conne+ting Leads -- --

T"EOR#:

Thevenins theorem is ver# use,ul in anal#ing the voltages in a net!or.' Thetheorem states that

Any circuit having a number of voltage sources, resistances and open output

terminals can be replaced by a simple equivalent circuit consisting of a single voltage

source VTHin series with a resistance RTH, where the value of the voltage source is

equal to the open circuit voltage across output terminals and resistance is equal to

the resistance seen into the network across the output terminals!

Let the net!or. e re"resented # a lo+. in ,igure +onsist o, a +om"li+ated net!or.

+ontaining some resistan+es and voltage sour+es'

A++ording to thevenins theorem the entire net!or. +an e re"la+ed # a single

sour+e %T2!ith a series resistan+e RT2 as sho!n in ,igure'

Thevenizing a circuit:

Consider the net!or. as sho!n in ,igure A'

3e !ant to ,ind out the voltage %La+ross RLand its +urrent 4L'

To use Thevenins Theorem 5is+onne+t RL'

The t!o o"en ends then e+ome terminals a 6

'

7o! !e ,ind the thevenins e8uivalent et!een

a 6 i'e' 9o"en the "art o, the +ir+uit to e

anal#ed and 9thevenie: the remaining o, the

+ir+uit +onne+ted to the t!o terminals:'7o! aim is to ,ind %T2 a+ross a and RT2'

age 1 o, $

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Diagram B

Diagram C

Diagram D

ASCT/EEE/LAB/BEE-10

(Thevenins Theorem)

A,ter dis+onne+ting RL the +ir+uit e+omes as

sho!n in ,igure B'

7o! the voltage a+ross R&is same as o"en +ir+uit

voltage a+ross a 6 '

There,ore;

( )&1

&

&

RR

RVVVVRabTH

+

===

This voltage is "ositive at terminal a'

7o! to ,ind RT2 dis+onne+t RL6 short +ir+uit %' the +ir+uit e+omes as sho!n in

,igure C'

The e8uivalent +ir+uit thus e+omes as sho!n in

,igure 5'

7o! to ,ind voltage %L a+ross RL +onne+t RL at

terminals a-' B# using voltage 5ivision ,ormula theremaining +ir+uit +an e solved'

"TH

"TH

"

RR

RVV

+

=

6"

"

"

R

V# = '

PRO$E!URE:

Con,igure an# +ir+uit using resistan+es and voltage sour+es as

sho!n in ,igure'

Aim is to +al+ulate voltage a+ross resistan+e R$(a+ross terminals a 6 )'

1' a.e "o!er >>>>> volts'

$' ?sing Thevenins Theorem +al+ulate voltage a+ross terminals a 6 as under'

a. Calculation o !T".

Ta.e out resistan+e R$'

easure %T2a+ross

terminals a 6 '

%T2 = >>>>> volts'

age & o, $

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ASCT/EEE/LAB/BEE-10

(Thevenins Theorem)

Theoreti+all#( )

*@A&1

A&

RRRRR

RR$VTH

++++

+=

Com"are %T2measured !ith %T2+al+ulated (it should e same !ithin

"ra+ti+al limitations)'

#. Calculation o RT":

Short +ir+uit the Sour+e 9E: 6

ta.e out R$to +al+ulate RT2 as

sho!n in ,igure'

( ) ( )

@*1A&

@*1A&

RRRRR

RRRRRR

TH

++++

+++=

7o! using Thevenins Theorem

%oltage a+ross R$ %ABis

$

$

$

RR

RVVV

TH

TH

RA%

+

==

Com"are the voltage measured in

ste"-& !ith voltage %R$'

O%SERVATION TA%&E:

S. No. VT" RT"1.

&'

RESU&T:

Both the values are +om"arale !ithin "ra+ti+al limitation' 2en+e Thevenins

theorem is veri,ied'

PRE$AUTIONS:

1' Avoid an# loose +onne+tions'

&' ?se instruments o, "ro"er range'

age $ o, $