Page "Electricity" Paragraph 59

The inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current through it.

When the current changes, the magnetic field does too, inducing a voltage between the ends of the conductor.

The induced voltage is proportional to the time rate of change of the current.

The constant of proportionality is termed the inductance.

The unit of inductance is the henry, named after Joseph Henry, a contemporary of Faraday.

One henry is the inductance that will induce a potential difference of one volt if the current through it changes at a rate of one ampere per second.

The inductor's behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current, but opposes a rapidly changing one.