How a Relay Works

A relay is an electromechanical switch. It works in the same way as a manual switch. It is very useful not only for turning the power of a device on and off automatically but also for switching higher power devices with a low power. 

An electromagnet is a simple device made up of a wire wound in a coil around a core of ferromagnetic material. To create your own electromagnet, a nail and some insulated wires are enough. Wind the wire into a coil around the nail and apply power. Attention, it can be very hot if you have too few windings or too much voltage!

When a wire conducts current, it produces a magnetic field. If we wind a wire into a coil around a core of ferromagnetic material such as iron, we magnify this field and we get an electromagnet with enough magnetism to do some interesting stuff.

Notes of caution: Always check the voltage and current rating of the relay switch. Some are designed for switching low voltages only, while others are meant for switching higher voltages.
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