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 potentionmeter should have voltage of 8 V
B. The battery of potentionmeter can have a voltage of 15V and R adjusted so that the potential drop across the wire slightly exceeds 10 V
C. The first portion of 50cm 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 potentiometer 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. As values of emfs of two cells are approximately 5V and 10V, therefore, the potential drop along the potentiometer wire must be more than 10V. Hence, option (b) is correct.