The AC generator
- If a coil of wire is rotated inside a magnetic field by an external force, an e.m.f. will be generated in the wire which causes current to flow within the coil
- A simple A.C. generator converts mechanical energy into electrical energy in the form of alternating current
An alternator is a rotating coil in a magnetic field connected to commutator 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 (or commutator rings)
- The slip rings and brushes provide a continuous connection between the coil and the meter
- When 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 a potential difference, 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 potential difference in the coil repeatedly changes its direction
- This continues as long as the coil keeps turning in the same direction
- The induced potential difference and the current alternate because they repeatedly change direction
As the coil rotates in the magnetic field, the changing magnetic flux causes the induction of e.m.f. in the opposite sides of the coil