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Skin effect
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AC concentrates near the conductor surface.
At high frequency AC concentrates near the surface of a conductor; skin depth δ = √(2ρ/ωμ). For copper at 50 Hz it's 9 mm; at 1 MHz 66 μm.
High-frequency cables use hollow or stranded conductors.
Raises effective resistance.
In more detail
The skin effect causes alternating currents to flow mainly near the surface of a conductor at high frequencies. This reduces the effective cross-section and increases resistance.
Real-world uses
- High-frequency cables use stranded or hollow conductors to manage skin effect.
- RF engineers account for skin effect in antenna design.
- High-frequency currents in a wire flow mainly near its surface, which is why thick cables are not always best for radio.
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Frequently asked questions
What is the skin depth?
The depth at which the current density falls to about 37% of its surface value.
Why does frequency matter?
Higher frequencies produce a thinner skin depth, increasing resistance.
Why does skin effect matter?
It increases the effective resistance at high frequency, so engineers use stranded or hollow conductors for radio frequency work.
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