Red Seal Electrician Practice
TransformersQuestion 1105 of 1506

What is an autotransformer?

  1. A transformer with two windings and a shielded core for noise
  2. A transformer with an air core and a single tapped primary
  3. A transformer that makes DC from an AC supply with no diodes
  4. A transformer with one tapped winding and no isolation
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Correct answer: A transformer with one tapped winding and no isolation

An autotransformer uses a single winding for both input and output. It steps voltage up or down but does not isolate.

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

Practice transformers

Questions last reviewed: 18 October 2026