Application of a Potentiometer—

1. Measurement of emf of a cell
2. Comparison of emfs of two primary cell
3. Measurement of Internal Resistance if a cell

Measurement of emf of a cell—

Potentiometer—

A potentiometer is a device used to measure the potential difference between two points or the unknown emf.

Principle-

When a uniform current flows through a uniform wire the potential drop across any length is directly proportional to the length of the wire.

Construction-

Efficiency of a Source—

The efficiency of a source is defined as the ratio of the output power to the input power.

Let a voltage source of emf ‘E’ and internal resistance ‘r’ is connected to the resistance ‘R’ so that current ‘I’ is flowing through it, then efficiency

Efficiency of an Electrical Device—

Electric Power—

The rate of work done by the voltage source to flow the current in the circuit is called electric power of the circuit or the rate of heat produced in the resistor is called its electric power.

Definition of One Watt—

If W= 1 J and t= 1s then P= 1W

If an appliance consumes one joule of energy in one second then its power is called one watt.