A unit of electromotive force is called what?

A unit of electromotive force is called a volt.

The volt is the SI derived unit for electromotive force, electric potential, and potential difference. Its symbol is V, and one volt equals one joule of energy per coulomb of electric charge. In circuit terms, it describes the electrical “push” that can drive current through a conductor.

The unit is named after Italian physicist Alessandro Volta, whose voltaic pile, developed around 1800, was an early practical battery. The volt was formally adopted as an electrical unit by the International Electrical Congress in 1881.

A common mix-up is confusing volts with amps and watts. Volts measure electrical potential difference, amperes measure current, and watts measure power. For example, a 12-volt battery supplies a potential difference, while the actual current depends on the circuit connected to it.