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What is a Power Relay?
A power relay is a switch that uses an electromagnet to open or close a circuit. The basic design of a relay utilizes an electromagnet coil, an armature, a spring and one or more contacts. If the power relay is designed to normally be open, the circuit is not completed when in the off state.
As power is applied to the power relay, generally from a battery source, the electromagnet attracts the armature, a movable arm often made of iron. The armature, which was held in place by the spring, is pulled in the direction of the coil until it reaches a contact, thus closing the circuit. If the relay is normally closed, then the coil pulls the armature away from the contact, opening the circuit.
A power relay can be operated using a low amount of voltage but can also conduct a higher amount of voltage. For this reason, power relays are used for many different applications, including audio amplification, automotive electronics and telephone systems. Power relays were also used in early computer systems and in telegraph systems to relay the signal from one circuit to the next.
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