Question

Two cells of emf’s approximately 5V and 10V are to be accurately compared using a potentiometer of length 400 cm.

Options

• The battery that runs the potentiometer should have voltage of 8V.

• The battery of potentiometer can have a voltage of 15V and R adjusted so that the potential drop across the wire slightly exceeds 10V.

• The first portion of 50 cm of wire itself should have a potential drop of 10V.

• Potentiometer is usually used for comparing resistances and not voltages.

Answer 1

The battery of potentiometer can have a voltage of 15V and R adjusted so that the potential drop across the wire slightly exceeds 10V.

Explanation:

The potential drop along the wires of potentiometer should be greater than emfs of cells.

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. Here, values of emfs of two cells are given as 5V and 10V, therefore, the potential drop along the potentiometer wire must be more than 10V.