Question

Why is potentiometer preferred over a voltmeter for comparison of emf. of cells?

Answer 1

Potentiometer is preferred over a voltmeter for comparison of emf of cells because of the following reasons:
(a) A potentiometer can measure the internal resistance of the cell, which a voltmeter cannot measure.
(b) A potentiometer can accurately measure small potential differences, which a voltmeter cannot.
(c) The accuracy of a potentiometer can also be increased by increasing the length of the wire, whereas the accuracy of the voltmeter is fixed.