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GCSE Physics · key term
A generator that produces alternating current.
Used by AQA, Edexcel and OCR
Specification 4.7.3.2 · Paper 2
Revise: Uses of the generator effectIn a simple alternator, the rotating coil connects to two separate slip rings. Each end of the coil remains attached to the same ring, while stationary brushes connect the rings to the external circuit.
Specification 13.3P · Paper 2
A generator that produces a current which repeatedly reverses direction.
Revise: Alternators and DynamosNeither an alternator nor a dynamo needs an electrical supply to start that current: the coil is turned by an external source of mechanical energy.
Specification P4.2f · Paper 1 (Foundation), Paper 3 (Higher)
A generator that produces alternating current by converting mechanical energy into electrical energy.
Revise: Alternators and dynamosIn an alternator, each end of the coil remains connected to the same external terminal through a separate slip ring and contact. The reversal in the coil therefore appears at the external terminals. When a circuit is connected, its current repeatedly reverses direction: this is alternating current (a.c.).
Paper 1, Paper 2
A generator whose output potential difference repeatedly reverses polarity, producing alternating current in a complete circuit.
Revise: Alternators and DynamosAn alternator produces an alternating p.d. Its p.d.–time graph has time on the horizontal axis and p.d. on the vertical axis. A trace above zero represents one polarity; a trace below zero represents the opposite polarity.
For an alternator, link the reversing motion of the rotating coil to an induced current that changes direction every half-turn.
Explain what happens at the external terminals, not just in the rotating coil: an alternator’s output reverses direction; a dynamo’s does not.
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