Red Seal Electrician Practice
AC theoryQuestion 952 of 1506

A solid copper conductor carries high-frequency AC. Where does most of the current flow?

  1. Evenly through the whole cross-section
  2. Mainly through the centre of the conductor
  3. Near the outer surface of the conductor
  4. Only in the insulation around the conductor
Show answer

Correct answer: Near the outer surface of the conductor

This is the skin effect. AC avoids the centre and stays near the surface, so the AC resistance is higher than the DC resistance.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 3.6: What Is the Skin Effect? The Skin Depth of Copper in Electrical Engineering

Practice ac theory

Questions last reviewed: 18 October 2026