Question

How is potentiometer superior than voltmeter

Answer 1

In case of voltmeter there may be some error in reading the deflection .On the other hand for measuring the emf by a potentiometer only null point is to be read which involves less error.Also,for measuring emf of a cell by a potentiometer in the position of null point ,no current flows in the circuit.So cell remains in open circuit.Therefore we get the actual value of emf.

Therefore a potentiometer is superior to a voltmeter.