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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: You left out topology--the physical design and / or weaving. posted by John Marks on August 1, 2022 at 06:46:04:
In lamp cord there isn't a hot and cold wire running in parallel. The current (actually electrons) runs on both wires, that's how AC works. What Heaviside was describing is the "energy flux density" not electromagnetic flux. The so-called "Poynting vector" points in direction of electron motion. Electric fields and magnetic fields alternate E, B, E, B, etc. along both wires constantly, the directions opposite each other and alternating. The energy of the signal is contained in the E and B fields, which lie outside the metal conductors, the units of Poynting vector are Watts per meter squared.Current actually doesn't flow along wires, current is a calculated quantity that has no velocity or direction. It's a scalar quantity. The current is calculated by adding up all the moving free electrons for the cross-section of the conductor. Thus thicker conductors support higher currents. The only thing actually moving is electrons, and they don't move fat or far. One meter per hour and about a millionth of an inch at one time (half cycle) depending on instantaneous audio frequency in speaker cables. Does that surprise you? For power cords the electrons would travel a little farther each half cycle since the rate of alternation 60 Hz is slower than for speaker cables.
The direction of electric and magnetic fields are perpendicular to each other and to direction of electron flow. The magnetic field B is induced by moving charges (I.e., free electrons) and the electric field is induced by the voltage.
The difference between power cords and speaker cables is basically that rate of alternation, 60 times per second for power cord and whatever the instantaneous audio frequency is, nominal 20-20k times per second (Hertz) for speaker cables.
Edits: 09/29/22 09/29/22 09/29/22
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- RE: You left out topology--the physical design and / or weaving. - geoffkait 14:54:23 09/29/22 (0)
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