2. Relay • A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. • A relay is a small electromagnet which can be used to switch on a large current in a circuit using a small current. For example, a relay is used to switch on the current (usually very large) in the starter motor of a car.

3. The circuit diagram The circuit connections are shown in Fig. 12. • When the key is turned (closed), a small current flows through the relay coil. This will energize the magnet in the relay, which then will attract the pivoting armature. As the armature moves, the contact closes and a current flows in the circuit, which will start the motor. Thus a relay acts as a output transducer, which converts electrical energy to mechanical energy.

4. How it works? • http://www.youtube.com/watch?v=Mci7gysJtI4