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A relay is a DC operating switch, which opens and closes another circuit. The relay is (1) _____ another circuit with a higher current. The other circuit current (2) _____.

  • A

    (1) connected to; (2) can only be DC

  • B

    (1) connected to; (2) can be AC or DC

  • C

    (1) separated from; (2) can only be DC

  • D

    (1) separated from; (2) can be AC or DC

LO 021.09.01.06.04: Explain the purpose and the working principle of a relay.

Refer to figure.
The figure shows a typical relay arrangement. The purpose of a relay is to separate the control circuit from a high-voltage load circuit. It works through a low voltage DC circuit which controls an electromagnetic relay contact. When the low voltage control circuit is energised, it closes the contacts to close the higher current loop.

The higher load circuit can be either DC or AC. The purpose of separating the circuits is to protect the controller, especially if it is a human user, from the high current of the load circuit.

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