Answer: Increasing frequency.
- A Increasing frequency
- B Decreasing frequency
- C Increasing resistivity
- D No relation to frequency
Correct answer: A. Increasing frequency
Explanation: Skin depth δ = √(2ρ/μω) where ρ is resistivity and μ is permeability. At high frequency, δ decreases. This skin effect causes AC to flow near the conductor surface.
In a pure inductor the current lags the voltage by 90° (energy is briefly stored in the magnetic field before current responds); in a pure capacitor the current leads the voltage by 90° (current must flow to build up charge before voltage rises) - the mnemonic "ELI the ICE man" keeps these straight.
Concept context
AC circuits, impedance, LCR series circuit, resonance, transformers, and power factor.