Red Seal Electrician Practice
TransformersQuestion 1090 of 1506

A technician claims a transformer can deliver more output power than the input power, because the voltage is stepped up. Why is this wrong?

  1. Stepping up the voltage always cuts the current to zero in the secondary.
  2. A transformer only converts power. It cannot create it.
  3. The core stores the extra power as heat and releases it to the load later.
  4. Transformers only work on DC circuits and so cannot be compared this way.
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Correct answer: A transformer only converts power. It cannot create it.

Power is voltage times current. When the voltage goes up, the current goes down. Output power cannot be more than input power.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 10.2: Step-up and Step-down Transformers

Practice transformers

Questions last reviewed: 18 October 2026