In a circuit, electromotive force is the energy per unit charge converted from the other forms of energy into electrical energy to move the charge across the whole circuit.
Definition
The electromotive force (e.m.f.) is defined as the energyper unit charge that is converted from chemical, mechanical, or other forms of energy into electrical energy in a battery or dynamo.
Definition
The potential difference (p.d.) between two points is defined as the energy converted from electrical to other forms when one coulomb of positive charge passes between the two points.
Terminal potential difference or terminal voltage is the potential difference across the two terminal (the positive terminal and the negative terminal) of an electric source (cell or generator).
If the internal resistance of the cell is ignored, the terminal potential difference is equal to the e.m.f.