Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!sdd.hp.com!hplabs!hpfcso!hpfcdj!myers From: myers@hpfcdj.HP.COM (Bob Myers) Newsgroups: sci.electronics Subject: Re: Gold saves energy. Message-ID: <17660169@hpfcdj.HP.COM> Date: 6 Jun 91 17:44:12 GMT References: Organization: Hewlett Packard -- Fort Collins, CO Lines: 27 >Are you sure? I thought AC travelled on the surface of the wire, not >in the bulk, or is this just a very high frequency phenomenon? In You're referring to the "skin effect," which is dependent both on the frequency in question and the conductive material. In copper at 60 Hz, the skin effect is pretty much negligible. The formula for the skin depth - in millimeters - for copper is depth = 66.1/SQRT(f), with f being the frequency in Hz. For 60Hz, then, we have a skin depth of 8.53 mm, or about 1/3 in. Any practical plating of the wire, even if it were with a material of significantly better conductivity than aluminum (and gold *isn't*) simply wouldn't be worth the effort. Such "plated" wires (although I'm not sure that's how they're manufactured) are in use, however. For example, a type of wire called "copperweld," which has a copper cladding over a steel core, is widely used for antennas and other RF applications; the copper handles the RF energy, while the steel provides strength. A similar construction is used in some power-line cases, with a steel core surrounded by copper or aluminum strands, and for the same reason. A good question, though. Bob Myers KC0EW HP Graphics Tech. Div.| Opinions expressed here are not Ft. Collins, Colorado | those of my employer or any other myers@fc.hp.com | sentient life-form on this planet.