Question

Why is a potentiometer preferred over a voltmeter for measuring emf?

Answer 1

A voltmeter to Potentiometer should have an infinite resistance so that it draws no current from the circuit. However, a potentiometer cannot be designed to have infinite resistance. At the null point, a potentiometer draws no current from the circuit, providing a more accurate measurement. As a result, it serves as an ideal voltmeter.

Answer 2

Potentiometer preferred over a voltmeter for measuring emf due to following reasons:

1. The potentiometer is more sensitive than a voltmeter.
2. A potentiometer can be used to measure a potential difference as well as an emf of a cell. A voltmeter always measures terminal potential difference, and as it draws some current, it cannot be used to measure an emf of a cell.
3. Measurement of potential difference or emf is very accurate in the case of a potentiometer. A very small potential difference of the order 10^–6 volt can be measured with it. The least count of a potentiometer is much better compared to that of a voltmeter.