Question

You are asked ot measure e.m.f of a cell. Which instrument will you use? A high resistance Voltmeter or Potentiometer and why?

Answer 1

We will use potentiometer because potentiometer draws no current while measuring the emf of the cell

Or Simple answer would say: it is because potentiometer doesnt draw any current for itself from the primary circuit and hence gives more accurate measurement thereby acting as an ideal voltmeter. It uses null method to measure.

A detail answer would say:

Voltmeter is a device used to measure the potential difference between two points in an electrical circuit. On the other hand a potentiometer is a device which is used as an adjustable voltage divider in a circuit. It is similar to the rheostat or variable resistor. It is much commonly used in volume controllers and joysticks. Thus in a voltmeter voltage cannot be divided whereas in a potentiometer voltage can be divided.