In electromagnetism and electronics, electromotive force (also electromotance, abbreviated emf, denoted E ) is an energy transfer to an electric circuit per unit of electric charge, measured in volts. Devices called electrical transducers provide an emf by converting other forms of energy into electrical energy. Other electrical equipment also produce an emf, such as batteries, which convert chemical energy, and generators, which convert mechanical energy. This energy conversion is achieved by physical forces applying physical work on electric charges. However, electromotive force itself is not a physical force, and ISO / IEC standards have deprecated the term in favor of source voltage or source tension instead (denoted U s ).