Q. 283.8( 54 Votes )
State working pri
The potentiometer is the device which is used to measure the potential difference with high accuracy. It is used compare emf of two cells, measure emf of the cell and to determine the internal resistance of a primary cell.
It works on the principle that for the uniform wire, the potential difference across any two point on it is directly proportional to the length between the two points.
If the value of R is 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 because E= kl. According to this relation, 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 and shift towards I.
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