Electric current Electric current An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionised gas (plasma). The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second. Electric current is measured using a device called an ammeter. Electric currents cause Joule heating, which creates light in incandescent light bulbs. They
History of the metric system the Treaty of the Metre was extended to cover electrical units with the CGPM merging its work with that of the IEC. The twentieth century history of measurement is marked by five periods: the 1901 definition of the coherent MKS system; the intervening 50 years of coexistence of the MKS, cgs and common systems of measures; the 1948 "Practical system of units" prototype of the SI; the introduction of the SI in 1960; and the evolution of the SI in the latter half century. The need for an orthogonal electromagnetic unit to resolve the difficulties of defining such units in