the basic unit of electric current intensity, equal, in the MKS system, to a rate of flow of charge in a conductor or conducting medium of one coulomb per second and, in the SI system, to a constant current that, if maintained in two straight parallel conductors of infinite length and negligible circular cross section placed one meter apart in a vacuum, would produce between these conductors a force equal to 2×10 newton per meter of length: abbrev. A or amp