Self-inductance

In electromagnetism and electronics, inductance is the property of an electrical conductor by which a change in current through it induces an electromotive force in both the conductor itself and in any nearby conductors by mutual inductance.

These effects are derived from two fundamental observations of physics: a steady current creates a steady magnetic field described by Oersted's law, and a time-varying magnetic field induces an electromotive force (EMF) in nearby conductors, which is described by Faraday's law of induction. According to Lenz's law, a changing electric current through a circuit that contains inductance induces a proportional voltage, which opposes the change in current (self-inductance). The varying field in this circuit may also induce an EMF in neighbouring circuits (mutual inductance).

The term inductance was coined by Oliver Heaviside in 1886. It is customary to use the symbol L for inductance, in honour of the physicist Heinrich Lenz. In the SI system, the measurement unit for inductance is the henry, with the unit symbol H, named in honor of Joseph Henry, who discovered inductance independently of, but not before, Faraday.

An electronic component that is intended to add inductance to a circuit is called an inductor. Inductors are typically manufactured from coils of wire. This design delivers two desired properties, a concentration of the magnetic field into a small physical space and a linking of the magnetic field into the circuit multiple times.

The relationship between the self-inductance, L, of an electrical circuit, the voltage, v(t), and the current, i(t), through the circuit is

A voltage is induced across an inductor (back EMF), that is equal to the product of the inductor's inductance and the rate of change of current through the inductor.

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