Question

The instrument for the accurate measurement of the e.m.f of a cell is ______.

Options

• a voltmeter

• an ammeter

• a potentiometer

• a slide wire bridge

Answer 1

The instrument for the accurate measurement of the e.m.f of a cell is a potentiometer.

Explanation:

Potentiometers and voltmeters are both devices used to measure potential differences. The terminal potential difference between the electrodes of a cell in an open circuit, i.e. when no current is flowing from it, is known as the emf. Potentiometers use the null deflection method to measure potential differences, which means no current is pulled from the cell, whereas voltmeters require a tiny current to demonstrate deflection. As a result, a potentiometer is used to accurately measure p.d.