Simple A.C Generators
- The generator effect can be used to generate a.c in an alternator
- A simple alternator is a type of generator that produces an alternating current
Structure of an Alternator
An alternator is a rotating coil in a magnetic field connected to slip rings
- A rectangular coil is forced to spin in a uniform magnetic field
- The coil is connected to a centre-reading meter by metal brushes that press on two metal slip rings
- The slip rings and brushes provide a continuous connection between the coil and the meter
- The coil turns in one direction:
- The pointer defects first one way, then the opposite way, and then back again
- This is because the coil cuts through the magnetic field lines and an EMF, and therefore current, is induced in the coil
- The pointer deflects in both directions because the current in the circuit repeatedly changes direction as the coil spins
- This is because the induced EMF in the coil repeatedly changes its direction
- This continues on as long as the coil keeps turning in the same direction
- The induced EMF and the current alternate because they repeatedly change direction
Examiner Tip
Motors and generators look very similar, but they do very different things.
When tackling a question on either of them, make sure you are writing about the right one! A motor takes in electricity and turns it into motion. A generator takes in motion and generates electricity.
You might be expected to give explanations of how these two things happen - make sure that you understand their subtle differences!