6.12 understand why a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers
6.12 understand why a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers
Motor
Current flows in the wire/coil.
This creates a magnetic field around the wire/coil.
This magnetic field interacts with the field from the permanent magnet.
This produces a force on the wire/coil which moves the wire/coil.
The split-ring commutator changes the direction of the current every half turn as it spins. This reverses the direction of the forces, allowing the coil to continue spinning.
Loudspeaker
An alternating current from the source passes though the coils in the speaker.
This current is constantly changing direction and magnitude
This current creates a magnetic field around the coil
This field interacts with the magnetic field from the permanent magnets
Creating a constantly changing force on the coil.
This causes the coil to vibrate in and out as the direction of the force changes, moving the cone
The cone causes vibrations which we hear as sound waves.
