Spinning Magnet, Flowing Current

In the picture

1. 1The rotor magnet: a bar magnet that spins and carries its magnetic field around with it
2. 2The stator coils: fixed copper windings that the moving magnetic field sweeps through
3. 3The shaft: the turning rod that the turbine drives and that carries the magnet around
4. 4The output wires: two copper conductors that carry the changing current away from the coils
5. 5The lamp: a glowing filament that lights because the alternating current passes through it

Examples

• A bicycle dynamo lighting the front lamp as the wheel turns.
• A car alternator recharging the battery while the engine runs.

Quiz: Spinning Magnet, Flowing Current (Age 18)

1. 1

   What induces a voltage in the stator coils?

   • The fixed position of the copper windings.
   • The current flowing back from the lamp.
   • The changing magnetic field from the spinning rotor magnet.
2. 2

   Why is the output current called alternating current?

   • Because the magnet spins at a constant speed.
   • Because the coils are made of copper.
   • Because the current reverses direction each time the magnet’s poles pass a coil.
3. 3

   What happens to the induced voltage if the rotor magnet spins faster?

   • The voltage becomes higher.
   • The voltage becomes lower.
   • The voltage stops changing direction.

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.