Red Seal Electrician Practice
AC generationQuestion 907 of 1506

Why does the voltage from an alternator follow a sine wave?

  1. Flux change from a rotating magnet follows a sine function.
  2. The resistance of the coil varies as a sine function.
  3. The brush contacts shape the wave as they spin.
  4. The load current sets the shape of the wave.
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Correct answer: Flux change from a rotating magnet follows a sine function.

Voltage is proportional to the rate of flux change, and that rate varies as a sine for a rotating magnet.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 1.2: AC Waveforms

Practice ac generation

Questions last reviewed: 18 October 2026