06-10-11: HifihvnElizabeth's subsequent post provided a good answer as to the reason for the "close to it" part:
Almarg, would the close to it part be do to any resistance?
06-11-11: ElizabethThe number of electrons that are involved, btw, is far larger than the "well over a million trillion" that I mentioned in my first post near the start of this thread. That number referred just to the number of electrons oscillating back and forth across a single cross section of the conductors, over a very short distance. A similar number of different electrons would be oscillating back and forth across every other cross section spaced some small distance apart over the length of each conductor.
The number which would make the round trip might be some whole number, only because of the incredible number involved. So some, just because of random behavior, even though it is VERY unlikely, might just by chance manage the amazing feat.
06-11-11: ElizabethI don't think that a meaningful answer can be calculated, because drift velocity is proportional to current (see this Wikipedia writeup), and for such a small current drift velocity would become essentially zero.
How small a DC offset in volts, would be needed to allow an average of one electron per second to start the round trip from amp output to speaker, through speaker wires etc and back if the total distance traveled is 100ft. and how long would it take the electron, on average?
It should be noted, btw, that the 1 cm/hr figure that has been stated a number of times above will vary widely depending on current. As shown in the example near the bottom of the Wikipedia page, for 3 amps flowing through a 1 mm diameter (about 18 gauge) copper conductor, drift velocity is about 1 meter/hour. 3 amps rms corresponds to 72 watts into an 8 ohm load. A drift velocity of 1 cm/hr would correspond to a current of 30 milliamps in that size wire, which is 7.2 milliwatts into an 8 ohm load.
All in all, I'm starting to think that Bill (Audiofeil) had the best answer :-)
Regards,
-- Al