GCSE Physics (AQA)

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AC & DC Current Graphs

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Electricity Domestic uses and safety

AC & DC Current Graphs

3:13 Mains Electricity
Spec 4.2.3.1
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  • Direct current (DC) flows in the same direction but may vary in magnitude.
  • On a graph, DC is represented by plotting potential difference against time, with the positive direction above the graph.
  • A basic DC is shown by a straight line, indicating constant potential difference over time.
  • DC can change in potential difference but not direction, always remaining positive.
  • Alternating current (AC) has a changing potential difference, represented by a wave-like graph.
  • AC alternates between positive and negative values periodically.
  • Peak potential difference in AC is the largest positive or negative value reached.
  • Peak potential difference can be identified on a graph by extending lines from the wave's peaks or troughs.
  • AC alternates between positive and negative peak values, describing its behavior.
  • Peak potential difference of AC is slightly higher than the equivalent DC potential difference.
  • Equivalent DC is shown as a straight line on a graph, supplying the same power as the AC.
  • Frequency of AC is the number of times the pattern repeats in one second.
  • Frequency is measured in hertz (Hz), with one hertz equaling one cycle per second.
  • Higher frequency indicates more pattern repetitions in a given time.

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