How a loudspeaker works

1. An alternating current passes through the coil of wire. 

2. This will set up a changing magnetic field around the coil which will interact with the permanent magnetic field of the magnet.

3.Due to the motor effect, the coil will experience a changing force. The force will change in direction constantly, due to the alternating current. 

4. As the coil moves backwards and forwards, it is attached to the cone, so the cone vibrates backwards and forwards creating sound waves