Electromotive force

Electromotive force, abbreviated emf (denoted with \(\mathcal{E}\) and measured in volts) is the ratio between the work done by an electric generator to move the charges (conventionally positive) from the low electric potential pole to the pole with the highest electric potential, and the unit charge moved.

Although the electromotive force is not conservative, it is numerically equal to the maximum potential difference at the ends of an electric generator disconnected from the electrical circuit.

The use of the word force has a different meaning from that generally accepted today, that is to say of force in a mechanical sense; however, it is still applied, for example, to express the maximum potential difference that a voltage generator produces between its poles or the potential difference between the electrodes of an electrochemical cell. In particular, in the case of a galvanic cell, the electromotive force corresponds to the potential difference that occurs at the terminals of the open circuit cell (i.e. in the absence of current flow, or at equilibrium).