Can a Capacitor be fully charged?

Mr Al,

Thats interesting. So if we use the more accurate answer, we can prove that an estimate based on the order of magnitude of the charge with the simple exponential gives about the right answer. Thus, we dont have to worry that there is some unexpected significant delay for those last electrons. There is some delay, but not too much. Remember, nyaknyan expressed concern about this and wondered if his inital thought might have a flaw. It seems you have answered his concern. Very good.

steveB said:

Mr Al,

Thats interesting. So if we use the more accurate answer, we can prove that an estimate based on the order of magnitude of the charge with the simple exponential gives about the right answer. Thus, we dont have to worry that there is some unexpected significant delay for those last electrons. There is some delay, but not too much. Remember, nyaknyan expressed concern about this and wondered if his inital thought might have a flaw. It seems you have answered his concern. Very good.

Click to expand...

It should be emphasized that the slower rate of voltage difference between the capacitor terminals is due to the decrease in the rate of charge displacement, and not to the speed of charge movement. In other words, the slower change in voltage after many time constants is due to the lower current, and not the drift velocity of the electrons through the conductors.

Ratch

steveB said:

Mr Al,

Thats interesting. So if we use the more accurate answer, we can prove that an estimate based on the order of magnitude of the charge with the simple exponential gives about the right answer. Thus, we dont have to worry that there is some unexpected significant delay for those last electrons. There is some delay, but not too much. Remember, nyaknyan expressed concern about this and wondered if his inital thought might have a flaw. It seems you have answered his concern. Very good.

Click to expand...

Hi Steve,

First, thank you. I was really just following your idea though and trying to build on that line of thinking.
Also, as nyaknyan was asking in post #40, i think you are right that we answered the time delay question and also that the classic explanation is good enough for most purposes. To be specific to that post, i think the difference comes from how we view the electron 'pipeline'. If we viewed it as an empty open pipe with one electron shooting down it one at a time, then there would be a time delay based on how far it had to go too i think, but since the pipeline is always filled with electrons, i think that last electron can fall out in the time given which is not that long really (like 1 second for the given example).
As far as the lumped vs not lumped circuit analysis question that might come up, i think the initial rate would increase the delay by a very very small amount unless the cap was very far from the source, and would not effect the delay near the end of the period by anything at all, or at least not worth considering. So for the usual circuit we would probably be most concerned about, i think we have proved that the delay is finite as well as reasonable.