The unit of electric potential difference, or electromotive force (emf).A volt is equal to the difference in electric potential between two points in a circuit carrying one ampere (A) of constant current (I) across a resistance of 1 ohm, and thus dissipating one watt (W) of power.Voltage essentially is electrical pressure -- the higher the voltage, the greater the pressure forcing electrons to flow through a metallic circuit.The volt is named for Count Alessandro Volta (1745