Red Seal Electrician Practice
Safety and work practicesQuestion 1104 of 1506

An electrician must change the tap setting on a large power transformer to adjust for load changes. What must be true before the tap switch is operated?

  1. The transformer is at full load.
  2. The secondary is shorted.
  3. The primary is at half voltage.
  4. The transformer is de-energized.
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Correct answer: The transformer is de-energized.

Tap switches are usually not built to carry full-load current. They must be moved only with the transformer de-energized.

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

Practice safety and work practices

Questions last reviewed: 18 October 2026