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Cecil Moore wrote:
John Popelish wrote: Cecil Moore wrote: That is a false statement and is at the root of the misconceptions. Standing wave current does not have to be equal. I assume you are meaning that the RMS current at one physical point must not equal the RMS current at some other point. Yes, the RMS value of the standing wave current at the bottom of the coil doesn't have to bear any relationship to the RMS value of the standing wave current at the top of the coil. Aren't you claiming that the coil has transmission line like properties, in that it takes time for a wave to pass through it? Yes Any such device needs two mechanisms for storing energy, one magnetic (inductive) and one electrical (capacitive). Even free space has both. If you eliminate either mechanism (or make one of them insignificant, as would happen to the capacitance if the inductor approaches zero size), you lose the transmission line like properties as the dominant mechanism. There is no net charge carried over from cycle to cycle. Of course. no one is talking about the red herring of charge stored over a whole cycle. Everyone (except, possibly you) is talking about charge stored and recovered twice per cycle. There is no net storage of charge even if the steady-state RMS value of the standing wave current is zero at one end of the coil and 2 amps at the other end. And no one but you brings up "net storage". We are all talking about ordinary capacitive charge storage within a cycle. And there are two equal and opposite half cycles of that. If there is Ac voltage and capacitance to the universe, there is charge storage, twice within every cycle, one positive and one negative. The problem here is not how a coil works. The problem is how standing waves work. Standing waves have AC voltage swing. That applied to capacitance causes real charge storage and retrieval. Just as it does with traveling waves. How could the standing AC voltage not charge and discharge, charge the other direction and discharge every cycle, the capacitance between the conductor and the universe? Forget the coil. Start with a lossless unterminated transmission line and then step up to a 1/2 wavelength thin wire dipole. The capacitance in a lossless transmission line is between the two conductors. For the 1/2 wavelength thin wire dipole, the capacitance is to the surroundings. But the charge stored and dumped into that capacitance twice a cycle is very similar, except that in the case of the antenna, some energy leaves in the form of radiation. It is obvious that a number of people just don't understand the nature of a standing wave that doesn't move through a wire along with its phasor that doesn't rotate relative to the source. It is obvious to me that you are one of them. Every point on a line carrying a standing wave (except the node points) has AC voltage on it, and AC current through it. The amplitude and phase of those voltages and currents can be described as a phasor, with respect to some reference phase of the same frequency. As you move along the line, the amplitude changes and when you pass through a node the phase reverses. So the phasor does not rotate with position change, except for a step change of 180 degrees at nodes, rather than smooth rotation with respect to position. For a traveling wave, every point on the line has an AC voltage on it, and an AC current passing through it. The amplitude is constant along the line, but the phasor rotates as you move along the line (the phase is linearly dependent on position). But at any single point on the line, a non rotating phasor describes the amplitude and phase with respect to a reference phase of the same frequency. |
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