Ampere, AM pihr, is the unit used to measure the rate of flow of an electric current. It is one of seven base units in the metric system. There is an electric current of 1 ampere when 1 unit of electric charge flows past a cross section of an electric circuit in 1 second. The unit of electric charge is called a coulomb (see Coulomb). Thus, 1 ampere equals 1 coulomb per second. Physicists also define amperes in terms of the magnetic force produced by electric currents in parallel wires.