Question

A potentiometer wire, which is 4 m long is connected to the terminals of a battery of steady voltage. A leclanche cell gives a null point at 1m if the length of the potentiometer wire be increased by 1 m, What is the new position of the null point ? 

(A) 1.25 m 

(B) 1.4 m 

(C) 1.75 m 

(D) 1.2 m

Answer 1

The correct option is (A) 1.25 m.

Explanation:

EMF of cell = potential gradient × null point on the wire 

∴ (E/4) × 1 = (E/5) × x 

∴ (1/4) = (x/5) 

x = (5/4) = 1.25m