current in a wire produces a magnetic field, which can be made stronger by:
- increasing the current
- increasing the number of turns on the coil
- winding the coil around a magnetic material
When a conductor is in a changing magnetic field, a voltage will be induced in the conductor.
The magnetic field can change if:
- the conductor is moving in/out of a magnetic field
- a magnet is moving towards or away from the conductor
- a varying magnetic field
The size of the induced voltage in a coil can be increased by increasing the rate of change of the strength of the magnetic field, by having more turns on the coil and by having a coil of a greater area.
bicycle dynamo: changing magnetic field induces an alternating voltage in coil
generator: inducing a voltage using brushes sliding over slip rings.
The function of a transformer is to change the size of an alternating voltage. This is done by having two seperate coils with different numbers of turns.
input voltage / output voltage = primary turns / secondary turns
Vp / Vs = n₁ / n₂