- an electric conductor wound as a helix with small pitch, or as two or more coaxial helices, so that current through the conductor establishes a magnetic field within the conductor.
- a switch controlled by such an arrangement, in which a metal rod moves when the current is turned on: used in automotive starting systems.
- a space formed by the intersection of isobaric and isosteric surfaces.
- a coil of wire, usually cylindrical, in which a magnetic field is set up by passing a current through it
- a coil of wire, partially surrounding an iron core, that is made to move inside the coil by the magnetic field set up by a current: used to convert electrical to mechanical energy, as in the operation of a switch
- such a device used as a relay, as in a motor vehicle for connecting the battery directly to the starter motor when activated by the ignition switch
