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From: Bill KT4YE
Date: 14 Apr 2003
Time: 19:54:06
Remote Name: 12.93.229.130
A fair amount of criticism was posted on this forum regarding Dr. Kabbary’s article in last September’s Antennex about new EM Equations and DC Displacement Current. At the time, I was occupied with other matters and did not have much time to study his proposition.<><><><> After a re-reading, I wanted to comment that Dr. K is correct about at least one aspect of his article.<><><> In his article, he postulated that a moving charge, when viewed from a stationary point, will cause a time-varying E field at the stationary point. He is absolutely correct. <><><> However, this is not new. This is the energy transfer mechanism that is used in klystrons, traveling wave tubes and other vacuum tube microwave devices.<><><> In a klystron, for example, clouds of electrons – previously accelerated to relativistic speeds – pass THROUGH a capacitive structure. The distance between the plates (often called the gap) is dimensioned such that it takes exactly T/2 (nano)seconds for the electrons to pass, with T being the period of the frequency of interest. <><><> The gap capacitance, in conjunction with the inductance of the contiguous microwave cavity, forms a resonant circuit at the frequency of interest. Energy may be extracted from the resonant cavity in a variety of ways to perform various useful tasks – like heating leftover pasta!<><><>However, I believe that for Dr. K to characterize this interaction – in a conductor instead of in a vacuum – as being the sole mechanism for generating Displacement Current is in error. This is because electrons FLOWING in a conductor operate entirely too slowly to result in the near-instantaneous generation of the effect called “Displacement Current.” <><><>In fact, rather than DELETING a term from Maxwell, it may be necessary to ADD A TERM to take this phenomenon into consideration. <><><><> Unless, of course, what is called “Displacement Current” is, in actuality, a manifestation of an entirely different phenomenon. Like, maybe, a TEM wave? :) 73, Bill KT4YE