Question

Why potentiometer is preferred over voltmeter for measuring e.m.f?

Answer 1

1) Potentiometer give the exact value of potential difference across any two points in a circuit because it never draws any current from the circuit. But Voltmeter draws apart of the current so there is an error in measurement of the potential difference.

2) Potentiometer can be used for measuring the internal resistance of a cell and also compare the e.m.f. of two cells , which cannot be done with a Voltmeter.