How electromotive force generate?
Electromotive force (emf, \mathcal{E}) is a term used to characterize electrical devices, such as voltaic cells, thermoelectric devices, electrical generators and transformers, and even resistors. For a given device, if an electric charge Q passes through that device, and gains an energy W, the net emf for that device is the energy gained per unit charge, or W/Q. This has units of volts, or joules per coulomb, and hence can be thought of as a voltage induced by the device in question. Since force has the unit of the newton, emf is a misnomer, but one that over time has resisted change.
