Relay

A relay is an electrically controlled switch in which an input signal changes the state of contacts in another circuit. It can use a small control current to switch a separate, larger load.

Electromagnet: A magnet produced by electric current, often through a coil wound around a core. In an electromechanical relay, its magnetic field pulls the armature toward the coil.
Electric circuit: A connected path through which electric current can flow. A relay links a control circuit to a switched circuit while keeping their functions distinct.
Automotive relay: A relay designed to switch electrical loads in vehicles. Vehicles use these relays to control loads such as lamps, fans, and pumps.
Transistor: A semiconductor device that controls current or voltage and can function as an electronic switch. Transistors switch electronically, avoiding the moving contacts used by conventional relays.
Armature: A movable part that responds to magnetic force in an electrical machine or device. The relay armature transfers the electromagnet’s motion to its contacts.
Electric current: The rate at which electric charge flows through a conductor or other medium. Current in the relay coil or input determines whether its switching mechanism is activated.
Protective relay: A device that detects abnormal electrical-system conditions and initiates protective action. Protective relays command circuit breakers when faults threaten power equipment.
Thyristor: A semiconductor device that switches and controls substantial current, often remaining on after triggering. Thyristors offer solid-state power switching where relay contacts would move mechanically.
Electrical contact: A conductive interface that joins or separates parts of an electrical circuit. Relay contacts open or close the switched circuit as the mechanism moves.
Voltage: The difference in electric potential between two points. A relay coil is designed for a particular applied voltage that produces its operating current.

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