skin effectSkin effect is a tendency for alternating current ( AC ) to flow mostly near the outer surface of a solid electrical conductor, such as metal wire, at frequencies above the audio range. The effect becomes more and more apparent as the frequency increases. The main problem with skin effect is that it increases the effective resistance of a wire for AC at moderate to high frequencies, compared with the resistance of the same wire at direct current ( DC ) and low AC frequencies. The effect is most pronounced in radio-frequency ( RF ) systems, especially antenna s and transmission lines. But it can also affect the performance of high-fidelity sound equipment by causing attenuation in the treble range (the highest-pitched components of the audio). Skin effect can be reduced by using stranded rather than solid wire. This increases the effective surface area of the wire for a given wire gauge . Tinned wire should be avoided because tin has higher resistance than copper. In large RF antenna arrays, hollow tubing can be used in place of solid rods with little or no loss of efficiency; in this respect, skin effect is an asset. It also works in favor of the use of copper-clad steel wire for more modest antennas. Such wire is mechanically stronger than solid or stranded copper, because steel has a higher tensile strength than copper. The skin effect causes most of the current to flow through the copper cladding, which is a better electrical conductor than steel. Skin effect occurs with brief pulses of current , for the same reasons it occurs at high AC frequencies. This can save lives. If you are caught in a thundershower, you can take refuge in a car or other metal vehicle and be relatively safe even if you suffer a direct hit. The skin effect causes virtually all of the current to flow on the outside of the vehicle as it passes from cloud to ground. Also see ampere per meter squared , current , and radio frequency ( RF ).
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| Last updated on:
Sep 21, 2005 |
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