An ampere is the standard unit (SI unit) of an electric current. Practically the word ampere is shortened to amp. It is named after André-Marie Ampère (1775–1836), French mathematician and physicist. A current of one ampere is equal to a charge of one coulomb going past a point at a given second. It is also the current produced by the voltage (V) of one volt applied across a resistance (R) of one ohm.