Answer / ripul ghosh

nowadays 24V DC relays are used compared to 230V what was used before..relays are mainly there to isolate the controller from high power lines,
The signal from the controller will come to the relay and it will get energised to drive the output load.

Answer / nirmalya basu

to energise a output by plc and for its protection purpose
also.

Answer / ganesh

the relay works with AC and DC.
it provide the isolation between controller and devices works on ac and dc.
it is extremely useful when you need to control a large amount of current or voltage with small electrical signal.

Answer / suresh agravat

Example pressure transmitter input showing fiied full with liquid than send singnal through output to relay. When relay deenergised motor contactor not get supply and it will be motor or pump stop. Relay is basically on/off switch

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