High Quality Content by WIKIPEDIA articles! An induction coil or "spark coil" (archaically known as an inductorium or Ruhmkorff coil after Heinrich Ruhmkorff) is a type of disruptive discharge coil. It is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current (DC) supply. To create the flux changes necessary to induce voltage in the secondary, the direct current in the primary is repeatedly interrupted by a vibrating mechanical contact called an interrupter. Developed beginning in 1836 by Nicholas Callan and others, the induction coil was the first type of transformer. They were widely used in x-ray machines and spark-gap radio transmitters from the 1880s to the 1920s. Today their only use is as the ignition coils in internal combustion engines, and in physics education to demonstrate induction.