Unit 36—review questions 1. What is a relay? Electrical mechanism that uses small current in the control circuit to operate a valve switch in the operating circuit. 2. When checking the resistance of the different parts of a relay, what resistance should you expect for the coil, normally open contacts, and normally closed contacts? coil de-energized, the normally open contacts should read infinite Ω (OL) and the normally closed contacts should read 0 Ω. When the coil is energized, the readings reverse: the normally open contacts should read 0 Ω and the normally closed contacts should read infinite Ω (OL). They should never have a measurable resistance. 3. What is the difference between a light-duty and a heavy-duty relay? Light-duty relays can be energized with low voltage. Once energized, the relay’s contacts close a higher voltage circuit that energizes a coil on the motor contactor or starter. The coil on the motor contactor or starter operates like the coil on the relay. When the coil on the motor contactor or starter is energized
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- Summer '17
- Mr. McCoy
- Relay, LRA