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From: Bill KT4YE
Date: 25 Dec 2002
Time: 20:11:13
Remote Name: 12.93.230.223
Happy Holidays and Best Wishes for a Happy, Prosperous and Peaceful 2003. <><><><> I apologize for having left unanswered several posts regarding my Displacement Current article. However, the way I earn my living is as a florist, and the Holiday Season is a very busy one for me. <><><><> To recap, my article postulates that Displacement Current is an antiquated way of explaining how AC current can pass through a Capacitor’s “open circuit.” Instead, I believe, we should consider a capacitor to be a (often) small transmission line, with a TEM wave providing for the current flow. Nowhere (that I have seen) in transmission line theory does Displacement Current even appear; much less is it considered to be the means by which a transmission line actually operates. <><><><> This is Antennex, and the primary importance of Displacement Current (or the lack thereof) is in ANTENNA applications. Any antenna element attempting to USE Displacement Current must, of necessity, be a significant fraction of a wavelength in size. Under these conditions, the Electric Field, E is a function of both TIME and LOCATION. Put another way, E = f(t, x, y, z). <><><><> The primary response from the critics seems to be that – even in a TEM wave -- Epsilon dE/dt exists and this requires/implies Displacement Current. <><><><> In fact, some folks stated – in effect – that demonstration of this “fact” would be a relatively simple mathematical exercise. I asked one of the critics to show us the derivation, but he elected to sign off the discussion instead. <><><><> I would like to suggest that, when these x,y,z factors are applied to even a simple construct like a parallel plate transmission line or coax cable, the result will be at odds with the so-called “simple” expression of Maxwell’s Equation that we are all taught in University-level EM classes. <><><><> Would anyone like to demonstrate that Maxwell’s Equations are still intact when this simple case is analyzed? <><><> 73 Bill KT4YE