The problem I have with the thrust of Al’s post is that he seems to be making the argument that the audio signal - I.e., the electromagnetic wave, the photons - is independent of the copper conductor and only depends on the dielectric characteristics. If that were true then the sound would not (rpt not) be subject to the conductor variables of metal purity, type of metal, type of crystal structure (e.g., single crystal, long grain), diameter of conductor, cable geometry, cryogenics, and direction of the wire.No, I was not saying that or implying that. I was simply referring to the dependence of **propagation velocity** on the dielectric. And I was doing that to support the fact that the electromagnetic wave, which is what conveys energy and propagates at near light speed, propagates via the dielectric, not within the conductor.
As I said earlier in this and other threads:
... energy is being transferred ... in the form of an electromagnetic wave comprised of photons that is distinct from although intimately related to the AC current."Current," as thought of in the conventional sense involving movement of a certain quantity of electrons within a conductor, and therefore the electromagnetic wave associated with that current, are both affected by resistance, capacitance, inductance, and various other factors including many that you mentioned.
It is debatable how much of the electromagnetic wave travels outside the wire and how much inside fhe wire. Is it 80/20? 50/50?Putting aside the phenomenon of "superconductivity," the resistance of any conductor is not zero. Consequently if a conductor is conducting a current it will absorb a small fraction of the energy associated with that current, and convert it into heat. The resistance of the conductor will be (or at least should be) such that the energy absorbed by the conductor is extremely small. Since energy is conveyed by the electromagnetic wave, though, photons will carry whatever energy is absorbed by the conductor into the conductor. So photons "travel" inside the wire only to the small extent that energy is absorbed by the wire.
Al seems to be hedging his bet bet when he states the signal DOES NOT travel within the conductor, then immediately says it travels primarily outside the conductor.I used the word "primarily" for two reasons:
1)What I said just above about a small amount of energy being absorbed by the conductor.
2)Depending on the thickness of the dielectric, shielding that may be present, and other factors in the design of the cable some of the signal energy may propagate outside of the dielectric, in the air.
... this thread concerns power cords so it should be pointed out that there is no “audio signal” involved. Which begs the question what is the “signal” traveling down the power cord? Is it also an electromagnetic wave, like the “audio signal,” or is it something else?I was using the term "signal" to refer to the electromagnetic wave corresponding to electric current of any kind, that is being conducted via wires. Including AC power.
Regards,
-- Al