Explain the working of relays

Answer 1

In electronics:

A relay is an electrically operated switch that uses a small voltage/current to turn on/off a larger voltage/current.

They are typically used to reduce costs, in that making all the wiring in a device (house/car/aeroplane etc) able to cope with the maximum voltage/current is expensive.

It is perhaps cheaper to use low voltage/current wires for most of the system, and put in a relay so that the switch you press is then cheap, as it is low voltage, and the wiring is cheap for the same reason. The expensive (heavy) high voltage/current wiring is reduced to a minimum and can be run directly from source to device. To add to that answer:

The relay, normally, is a coil of wire connected to the lower voltage source, through which a metal rod is ran (simple electro-magnet) to conduct the magnetic influence caused by charging the coil of wire. This bar then reacts with a 'reed' (a metal arm, normally sprung or with a spring attached) to cause it to move and 'make' contact between itself and another high voltage source (as explained above). The "contacts" on the end of this reed are normally 'sized' based upon their voltage/current limits and the spring return time is often stated as 'activation time' or 'transition' times.