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An Induction coil or "spark coil" (archaically known as a Ruhmkorff coil) is a type of disruptive discharge coil. It is a passive electrical device used to produce high-voltage pulses from a low-voltage DC supply.
Additional recommended knowledge
An induction coil consists of two coils of insulated copper wire wound around a common iron core. One coil, called the primary, is made from tens or hundreds of turns of coarse wire. The other coil, the secondary, typically consists of many thousands of turns of fine wire. An electric current is passed through the primary, creating a magnetic field. Because of the common core, most of the primary's magnetic field couples with the secondary winding. The primary behaves as an inductor, storing energy in the associated magnetic field. When the primary current is suddenly interrupted, the magnetic field rapidly collapses. This causes a high voltage pulse to be developed across the secondary terminals through electromagnetic induction. Because of the large number of turns in the secondary coil, the secondary voltage pulse is typically many thousands of volts. This voltage is often sufficient to cause an electrical discharge, or spark, to jump across an air gap separating the secondary's output terminals. For this reason, induction coils were sometimes called spark coils. Most induction coils utilized a magnetically activated vibrating arm to rapidly connect and break current flowing into the primary coil.
The induction coil was discovered during early experiments with electricity by Nicholas Callan in 1836 at the St. Patrick's College, Maynooth and further refined by Heinrich Ruhmkorff and others. Induction coils were used to provide high voltage for early gas discharge and Crookes tubes and for X-ray research. They were also used to provide entertainment (lighting Geissler tubes, for example) and to drive small "shocking coils" and violet ray devices used in quack medicine. A type of disruptive discharge coil remains in common use as the ignition coil or spark coil in the ignition system of internal combustion engines. A smaller version is used to trigger the flash tubes used in cameras and strobe lights. They were used by Hertz to demonstrate the existence of electromagnetic waves, as predicted by James Maxwell, and by Tesla and Marconi in early wireless telegraphy. By about 1920 they were supplanted in wireless or radio work by vacuum tubes.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Induction_coil". A list of authors is available in Wikipedia.|