How Does An Automotive Relay Work?


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Taylor Edgar answered
A relay works by using an electromagnetic coil, an iron core and a moveable armature to open or close a switch and thereby complete or break an electrical circuit.

Generally what happens is that the armature is on a pivot and moves back and forth whenever an electromagnetic field is present. The field is switched on and off by energising the coil.

When the core becomes electromagnetic the armature moves and makes contact with a terminal which powers up whatever the relay controls.

In reality most relays contain two switches, a small control circuit to activate the the relay and a second switch that enables the larger current to power up the load. When the control switch is open, no electrical current can flow to the core, so the electromagnetic field is not produced and the armature won't be attracted by magnetism to move and close the gap to power up the load.

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