A potentiometer works on the principle that

A potentiometer is an ideal voltmeter since a voltmeter draws some current through the circuit while potentiometer needs no current to work. A potentiometer works on the principle of emf comparison. In working condition, a constant currant flows throughout the wire of a potentiometer is made of uniform material and cross-sectional area, and it has uniform resistance per unit length. The potential gradient depends upon the current in the wire. A potentiometer with a cell of emf 2 V and internal resistance 0.4 Omega is used across the wire AB . A standard cadmium cell of emf 1.02 V gives a balance point at 66 cm length of wire. The standard cell is then replaced by a cell of unknows emf e (internal resistance r ), and the balance. Point found similarly turns out to be 88 cm length of the wire. The length of potentiometer wire AB is 1 m . The value of e is

Potometer works on the principle of:

Prism works on the principle of :