Principle Of Potentiometer|| define potentiometer || State the working principle of Potentiometer explain with help of circuit diagram How the potentiometer is used to determine the internal resistance of given cells ?

 

*** State the working principle of Potentiometer explain with help of circuit diagram How the potentiometer is used to determine the internal resistance of given cells ?

Working principle of Potentiometer :-

The potential difference across any part of inform wire is directly proportional to its balancing length the current is constant.

V = iR
V = i ( l/A)
V = ( ie/A ). l
V =Φ l
" V " directly proportional to " l "
Determination of internal resistance of a given cell :-

**  A cell of e.m.f " E " and internal resistance " r " is to be determine connected across resistance Box to a key [ K2 ] show in figure.
** When key [ K2 ] is open jockey adjusted the wire balancing point is obtains as " l1 ".
" E1" directly proportional to " l1 ".
E1 = Φl1
*** When [ K2 ] is closed the cell sends a current into the resistance box V is the terminal potential the balance point obtain l2.

V is directly proportional to l2
V =Φl2
From(1)/(2)
E1/V = Φl1/Φl2
E1/V = l1/l2
In first case when K2 open
i = E1/R+r
When K2 close
i = V/R
V/R = E1/R+r
R+r/R = E1/V
1 + r/R = l1/l2
r/R = l1//2-1
r = R ( l1/l2-1 )
Precautions :-
** Jockey should be drogged long the wire.
** The current value should be as small as possible.

Principle Of Potentiometer:-

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