Red Seal Electrician Practice
TransformersQuestion 1109 of 1506

In a variable transformer with a sliding contact, what is needed on the winding?

  1. The winding must be enclosed in an oil bath to cool the contact.
  2. The winding must have no taps anywhere along its length.
  3. The area the contact sweeps must be bare, with no insulation.
  4. The contact must be held at ground potential at all times.
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Correct answer: The area the contact sweeps must be bare, with no insulation.

The moving arm must touch the turns directly. So the winding is bare where it sweeps.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 10.5: Winding Configurations

Practice transformers

Questions last reviewed: 18 October 2026