1. A switch that opens and closes contacts by the action of an electromagnetic element.
2. A relay in which current flow through a coil produces a magnetic field that results in contact actuation.
3. A device that opens or closes contacts by settling "moving" contacts against "fixed" contacts when current passes through an electromagnet.

The electric current sets up a magnetic attraction between the core of the electromagnet and a hinged arm to the tip of which is attached the "moving" contact.

The movement of the arm towards the core of the electromagnet brings "moving" and "fixed" contacts together.

When an electric current is withdrawn, a spring returns the arm to to its original position and the contacts separate.