induction coil

WordReference Random House Unabridged Dictionary of American English © 2025

induc′tion coil′, [Elect.]

1. Electricity a transformer for producing high-voltage alternating current from a low-voltage direct current, consisting essentially of two concentric coils with a common soft-iron core, a primary coil with relatively few windings of heavy wire, and a secondary coil with many turns of fine wire. Excitation of the primary coil by rapidly interrupted or variable current induces high voltage in the secondary coil. Also called Ruhmkorff coil. 

• 1875–80

Collins Concise English Dictionary © HarperCollins Publishers::

induction coil noun

1. a transformer for producing a high voltage from a low voltage. It consists of a cylindrical primary winding of few turns, a concentric secondary winding of many turns, and often a common soft-iron core
   Sometimes shortened to: coil