Electromagnetic Induction and the Generator Effect — AQA GCSE Physics (Separate)
Moving a conductor and a magnetic field relative to each other induces a potential difference — the basis of generators.
The generator effect
When a conductor moves relative to a magnetic field (or the magnetic field through a coil changes), a potential difference is induced across the conductor. If the conductor is part of a complete circuit, an induced current flows. This is electromagnetic induction.
There is no induced p.d. if there is no relative movement (a stationary wire in a steady field).
Increasing the induced p.d.
The size of the induced potential difference is increased by:
- moving the conductor or magnet faster,
- using a stronger magnet,
- using more turns on the coil, and
- increasing the area of the coil.
Reversing the direction
Reversing the direction of movement (or the field) reverses the direction of the induced p.d. and current.
Generators
- An alternator generates alternating current (a.c.).
- A dynamo (with a split-ring commutator) generates direct current (d.c.). Microphones use the generator effect to convert sound vibrations into electrical signals.
Exam tips
- Relative movement between a conductor and a magnetic field induces a p.d.
- No movement → no induced p.d.
- Increase the induced p.d. with faster movement, stronger magnet, more turns, larger area.
- Alternators produce a.c.; dynamos produce d.c.