A coil is an electrical conductor such as a wire in the shape of a coil, spiral or helix. coils are used in applications where electric currents interact with magnetic fields, in devices such as inductors, electromagnets, transformers, and sensor coils.

An electromagnetic coil is a device comprising two distinct elements: a conductor and a core. The conductor is most commonly made from solid copper wire, which is wrapped around a solid metal core. Each time the wire is looped around the core, it is called a turn. Multiple turns are considered to be a coil.

The most common use of an electromagnetic coil is that of an inductor that stores energy within its magnetic field. Considered a passive electrical component, an inductor has no gain and cannot control the directional flow of the energy. The way an inductor harnesses energy is by the electric current passing through its body.