ruhmkorff coil

An electrical device consisting of a single coil of conductive material, often surrounding a metallic core, designed to establish a strong magnetic field around the coil. Changes in the current flow through the coil cause fluctuations in the magnetic field that induce a voltage across the coil. Induction coils have many applications, especially in circuits that tune to signals of specific frequencies, as in radios. The ability of an induction coil to induce a voltage is called inductance, and is measured in henrys. Compare capacitor.

A type of transformer that changes a low-voltage direct current to a high-voltage alternating current. Induction coils are used for many purposes, especially as spark coils for firing spark plugs in automobile engines and starting oil burners.