What does the term emf refer to in a circuit?

The term emf, or electromotive force, refers specifically to the amount of energy provided per unit charge by a source of electrical energy, such as a battery or generator. It quantifies the energy transfer when a charge moves through the source, essentially describing how much energy is supplied to each Coulomb of charge. Thus, emf can be understood as the number of joules given to each Coulomb of charge, making it an important concept in understanding how electrical circuits operate.

In a circuit, this energy supplied by the emf can result in a voltage across components, but the term itself directly describes this energy per charge relationship rather than just the potential or voltage in use across the circuit elements.