"An induction coil or \"spark coil\" (archaically known as an inductorium or Ruhmkorff coil after Heinrich Ruhmkorff) 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."@en . . .