Question

Write down the principle of potentiometer. Why is it called an ideal voltmeter?

Answer 1

The principle of a potentiometer is that the potential dropped across a segment of a wire of uniform cross-section carrying a constant current is directly proportional to its length. The potentiometer is a simple device used to measure the electrical potentials.

Potentiometer is called as ideal voltmeter because it does not withdraw any current from battery, cell. other devices like voltmeter withdraw current from cell.

$V=E-ir$

$i=0$ in case of potentiometer

$V=E$(thus ideal voltmeter)