State working principle of potentiometer. Explain how the balance point shifts when value of resistor r increases in the circuit of potentiometer
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Answer:
potentiometer is a device which is used to measure the potential difference with high accuracy.it is used to compare emf of 2 cells, measure emf if the cell and to determine the internal resistance of a primary cell
it works on the principal of uniform wire,the potential difference across any point on it is directly proportional to the length btw the 2 points..
If the value of R increases,the current flowing through the wire will decrease..This will decrease the potential difference (V) across (AI) and therefore the potential gradient (k) will also decrease.At the null point,as the potential gradient has decreased,the value of l(AJ) will increase.it is bcz E=kl.. According to the realtion,for a given emf,if potential gradient is decreased,the value of l has to be increased.As the value of l is increased the null point/balance point( j )will also change nd shifts towards I.