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August 19th 04, 07:14 PM
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Telamon wrote:
clifto wrote: Telamon wrote: (Clay Denski) wrote: BUT, what I don't get is why the two do not interfere. Let me explain.. Take a timeslice of EM radiation hitting my recieving antenna at some moment. Some electrons in the antenna move up in response to experiencing some energy from "Talk" station that corresponds to a high point in the sine-wave. The same electron, though, is pulled down a bit in response to some EM hitting it from "Zeppelin". How does "Talk" not affect "Zeppelin" if both are shoving the same electron in my antenna? How does my radio figure out that an effect at the antenna is NOT an ordinary modulation of the "Talk" carrier wave but rather of some other one and therefore to be ignored? The induced "Talk" electrons are separate from the "Zeppelin" electrons. The two different EM waves generate two different RF currents or two different flows of electrons in the antenna wire. If you look at the generated voltage on the wire with a oscilloscope in the time domain then you are going to see the sum of both generated RF currents. However, if you looked at it with a spectrum analyzer you would still see them as separate signals in the frequency domain. The radio receiver is designed to see one narrow band of frequencies at a time so only one of the two is received while the other is rejected. "Pushing the electrons" is a red herring. All electromagnetic and electrostatic forces in the universe contribute to pushing those electrons. Remember that those electrons come from your antenna wire, not the distant forces; the forces move *your* electrons, they don't send electrons to your antenna. Where did I say that the electrons came from the EM wave? I used the word "induced." This discussion is about two forces acting on electrons in a wire. Let's not make it more complicated than necessary to convey the concept of how they simultaneously interact. Whoa, wait. I was augmenting what you said, not correcting anything. I replied to you because the OP's article didn't make it here. Don't get the impression I was trying to correct you about anything in my previous article. Sometimes it helps people to read two different explanations; it *always* helps me. You didn't say that the electrons came from the wave, but he seemed to have that impression. Basically, I wanted to get him off the idea of watching the electrons and into the frequency domain. Remember also that electricity isn't electrons, it's a flow of energy that can move electrons. So it's not necessarily the electron movement that we're interested in, it's the flow. Overquantize this concept and you won't recognize the forest because you're looking at a few trees. DC or AC a "current" is a flow or movement of electrons. Actually, no. It's been shown that comparatively few electrons actually move in conductors. Mostly, energy transfers from atom to atom by exciting the electrons in the outer valence shell to higher states of excitement. Current is a flow of *charge*. http://216.239.41.104/search?q=cache:s9R2v9DztcIJ:www.cs.man.ac.uk/Study_subweb/Ugrad/coursenotes/CS1222/electricity.pdf+basic+electricity&hl=en&ie=UTF-8 In ionized materials like semiconductors, electrons flow a lot more than in non-ionized materials like wire, and charge moves when electrons move and take their charge with them. But then you see the "band gap" voltage, the amount it takes to actually move the electrons; there is no "band gap" voltage in a wire. (Someone is bound to be able to explain that much better than I.) -- It's unfair to characterize Kerry as a flip-flopper. He's consistently in favor of marrying a rich widow and buying your way into the White House. -- Rex Tincher |
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