What is Electromotive Force? - QS Study
QS Study

Electrical energy is needed to produce electric current in a circuit. The electromotive force of an electrical energy source is defined as the work done by the source or the energy spent by the source in driving a unit positive charge from one point of the circuit to the same point by traversing the complete circuit along with the source.

If the work done is W J in bringing Q C of charge in a complete circuit, then the work done in bringing 1 C of charge is W/Q .

Therefore the electromotive force of the source, E = W/Q

Unit: The SI unit of electromotive force is JC-1 or volt (V).

The devices which can transform some other forms of energy into electrical energy they only have electromotive force. For example: cell, generator, etc. An electric cell converts chemical energy into electrical energy and a generator coverts mechanical energy into electrical energy. The electromotive force of a cell is the sum of the potential differences which develops in different parts of the circuit along with the cell.