Red Seal Electrician Practice
Magnetism and electromagnetismQuestion 894 of 1506

How is a variable inductor often made?

  1. By changing the colour of the wire insulation
  2. By tapping the coil or sliding the core in and out
  3. By heating the core with a heat lamp
  4. By changing the length of the supply cable to it
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Correct answer: By tapping the coil or sliding the core in and out

Turns and core material are two of the factors that set inductance, so changing them changes the value.

Source: Lessons in Electric Circuits I: DC (Kuphaldt), 15.3: Factors Affecting Inductance

Practice magnetism and electromagnetism

Questions last reviewed: 18 October 2026