Red Seal Electrician Practice
TransformersQuestion 1135 of 1506

In a power system, how do harmonic frequencies compare with the design frequency of a transformer?

  1. They are fractions of the line frequency, so they are lower.
  2. They are the same as the line frequency, so they add no heat.
  3. They are random and can be lower or higher than the line frequency.
  4. They are whole-number multiples, so they are always higher.
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Correct answer: They are whole-number multiples, so they are always higher.

Harmonics are multiples of the fundamental. Core and skin-effect losses rise with frequency, so heating grows.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 10.8: Practical Considerations - Transformers

Practice transformers

Questions last reviewed: 18 October 2026