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 10V
D. Potentiometer is usually used for comparing resistances and not voltages.

Answer

B

Explanation

In a potentiomater experiment, the emf of a cell can be measured, if the potential drop along the potentiometer wire is more than the emf of the cell to be determined. Here, values of emfs of two cells are given as 5V and 10 V, therefore,t he potential drop along the potentiometer wire must be more than 10V.