Advanced Qualification · A-001 Advanced theory · A-001-002-004
Why does most of an RF current flow within a very thin layer under the conductor's surface?
- A Because of heating of the conductor's interior
- B Because of skin effect
- C Because the RF resistance of conductor is much less than the DC resistance
- D Because a conductor has AC resistance due to self-inductance
Correct answer: B — Because of skin effect. From the official ISED question bank, verified word for word.
Why
At radio frequencies, changing magnetic fields inside a conductor push the current toward the outside, leaving the centre nearly empty; this phenomenon is called skin effect. The full explanation — and one for every question — is in Pro.
Practise this section
Advanced theory: time constants, reactance, impedance, resonance, Q, and the mathematics behind tuned circuits.