Loudspeaker

1.a current in the coil creates a magnetic field 2.the magnetic field interacts with the permanent magnet generating a force, which pushes the cone outwards 3. the current is made to flow in the opposite direction 4.the direction of the magnetic field reverses 5. the force on the cone now pulls it back in repeatedly alternating the current direction makes the cone vibrate in and out 6. the cone vibrations cause pressure variations in the air - which are sound waves