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#11
February 17th 04, 11:59 PM
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Cecil Moore wrote: Jim Kelley wrote: Cecil Moore wrote: That is what has been confusing you all along. No confusion here, Cecil. Wouldn't such a statement be considered by most to be ad hominem, i.e. about the person, rather than about the subject being discussed? You accuse people of doing it to you all the time, but never seem to be able to fess up to it yourself. It's not ad hominem if it's true, Jim. You have demonstrated a certain level of confusion about the direction of AC current travel (of which there are only two) in a wire. In a single source, single load configuration, instantaneous AC current is either flowing toward the load or toward the source. For a phasor current in a wire, phase is an imaginary concept which exists only in your mind's math model. It is simply an artifact of the math model which doesn't exist in reality. That's why I keep harping on the seduction by the math models. Ask yourself, exactly where does that one amp at 90 degrees exist and exactly how can you measure it? Why do you keeps saying the sign of the _cosine_ of the phase determines instantaneous direction? Because it's true, Jim. Given that the reference is the source at zero degrees, which indicates a forward direction for current flow, all other current phases are referenced to the source. i=I*cos(phase_angle) If the cosine of that phase angle is positive, by convention, the instantaneous AC current is flowing toward the load. If the cosine of that phase angle is negative, by convention, the instantaneous AC current is flowing toward the source. According to definition, current is a rate. That should be obvious from it's units of coulombs per second. Alternating current can be expressed as a rotating vector, or phasor. Yes, but it goes in only one of two directions at a time. That is what you are missing. There are only two directions possible in a wire. The direction of travel in that wire is the sign of cos(phase_angle) referenced to the source. i*cos(20) and i*cos(60) are traveling in *EXACTLY* the same direction. Until you comprehend that fact of physics, you will not understand the superposition of forward current and reflected current, which is the original point of confusion. When you take time to understand the basics, and comprehend the difference between a vector and a phasor, then we can return to the original argument. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
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