Two cells of emfs approximately 5V and 10V are to be accurately compared using a poteniometer of length 400 cm.

Options

A. The battery that runs the potentiometer should have voltage of 8 V
B. The battery of potentiometer can have a voltage of 15 V and R adjusted so that the potential drop across the wire slightly exceeds 10 V
C. The first portion of 50 cm of wire itself should have a potential drop of 10 V
D. Potentiometer is usually used for comparing resistances and not voltages

Answer

B

Explanation

In the experiment of a potentiometer, the potential drop across the potentiometer wire should be more than the emf of the cell, to be measured or compared. In this case, the two cells have the emfs fo 5 V and 10 V. Hence the P.D. across the potentiometer wire should be more than 10 V.