E.m.f. stands for "electromotive force" and refers to the electrical potential difference or voltage that drives current through a circuit. Despite its name, electromotive force is not a force in the physical sense, but rather a potential difference that arises from chemical reactions, magnetic fields, or other sources of electrical energy.
In a circuit, the electromotive force drives electrons from the negative terminal of the source to the positive terminal, creating a flow of current. The unit of electromotive force is the volt, which is defined as the potential difference that will produce a current of one ampere when a resistance of one ohm is connected across the two points.
It's important to note that the electromotive force is not the same as the potential difference or voltage across a circuit element, such as a resistor or capacitor. In some cases, the electromotive force may be greater or less than the voltage drop across the circuit elements, depending on the nature of the circuit and the components involved.