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GCSE Physics · key term
A potential difference that repeatedly reverses polarity, usually changing continuously with time.
Used by OCR
Specification P8.2h · Paper 2 (Foundation), Paper 4 (Higher)
Revise: AC vs DCWith an alternating voltage (a.c.), the polarity repeatedly reverses. One terminal is first positive relative to the other, then negative, and the pattern repeats. In a suitable complete circuit, the current therefore also repeatedly reverses direction.
Paper 1, Paper 2
An electrical supply whose polarity repeatedly reverses, causing the current in a connected circuit to change direction repeatedly.
Revise: Mains Electricity and Electrical SafetyThe domestic supply is alternating voltage (a.c.), with a frequency of 50 Hz and a potential difference of about 230 V.
Describe voltage, not just the shape of a graph: d.c. keeps the same polarity, whereas a.c. repeatedly reverses polarity.
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