directional cables?

It doesn't apply an electromagnetic wave as without a completed circuit such as connecting a cable between the source component and the downstream component, there will be no current flow.

Thank you for coming up with an example that conclusively proves my point. That flow is a poor choice to describe what we call AC current.

Conventional wisdom says, as you and others have pointed out, that in order to have current flow you must have a complete path. That is true in DC and because of that it makes sense to use the word flow with DC. However, something different is happening with AC.

Hook up a radio transmitter to a cable that is several wavelengths long but has no load, it is open. An EM wave will travel the length and reflect back to the source. Google "time domain reflectometer" for a practical application of this phenomenon. The effective load on the transmitter can be an open, a short, or something in between depending on the length of the cable. If the length is just right it will appear to the transmitter as a short and a lot of current will "flow." It can be measured and it will heat up the wire just as if it was terminated. How can that be? How can current "flow" when there is no complete path? Because the electron are vibrating on this open ended cable just like they are vibrating on one that is terminated with a short. As you just pointed out they are not actually flowing. They can't flow because the path is broken, yet I can measure the AC current because AC current is not really a flow.

http://www.microwaves101.com/encyclopedia/quarterwave.cfm

So why isn't that an issue with audio circuits. It would be if the cables were approaching a quarter wavelength but that would be several miles at audio frequencies so it doesn't cause any problems.

Here's an interesting read where the author discusses some of the many misconceptions about electricity. I'm not saying it is exactly what we are discussing here but I bring it up to illustrate that even though many of the ideas people consider to be common knowledge or conventional are in fact, wrong. http://amasci.com/miscon/elect.html In one section he makes the statement "In AC circuits the electrons don't flow forward at all, instead they vibrate slightly. The energy is carried by the circuit as a whole, not by the individual charged particles."

So much for that.
.

Herman

Thank you for coming up with an example that conclusively proves my point. That flow is a poor choice to describe what we call AC current.

Conventional wisdom says, as you and others have pointed out, that in order to have current flow you must have a complete path. That is true in DC and because of that it makes sense to use the word flow with DC. However, something different is happening with AC.

Nothing different happening with AC. At least not in this particular context, which I will remind you once again is audio cables. Specifically, analogue audio cables.

Yes, in order to have current flow you must have a complete path. But you're confusing having a complete path with a given electron flowing through the entire length of that path.

I have a battery. And a light bulb. I connect the light bulb to the battery with oh, let's say 100 feet of wire. The light bulb lights up. Ten seconds later, I disconnect the battery from the light bulb. The light goes out.

Was there ever any current flowing during that ten seconds? Of course there was.

However, the drift velocity of the electrons would have been slow enough that no given electron would have traveled more than a small fraction of the path.

Now let's connect the battery again but in the opposite polarity as before. Again, the bulb lights up. And ten seconds later I disconnect the battery.

As with before, no given electron ever travels more than a small fraction of the path. The only difference now is that they're flowing in the opposite direction from before.

Was there ever any current flowing during that ten seconds? Of course there was.

Now let's get fancy and hook up a switch between the battery and the wire that allows the battery's polarity to be switched. I flip the switch to one polarity for ten seconds, then the other polarity for ten seconds. Then back to the original polarity for ten seconds, and so on.

Was there ever any current flowing during those 10 second periods? Of course there was.

Now I do the same thing but at five second intervals. Was there current flowing? Yes. At one second intervals? Yes. At half second intervals? Yes. Quarter second? Eighth second? Sixteenth second? Yes. Yes. Yes.

Hook up a radio transmitter to a cable that is several wavelengths long but has no load, it is open. An EM wave will travel the length and reflect back to the source. Google "time domain reflectometer" for a practical application of this phenomenon.

I'm well aware of how TDR's work. In fact I've owned a couple in the past.

So why isn't that an issue with audio circuits. It would be if the cables were approaching a quarter wavelength but that would be several miles at audio frequencies so it doesn't cause any problems.

Right. But it IS audio circuits that we're discussing here. And my comments regarding current have all been within that context. And if you wish to address what I have said, then address it in the proper context.

I love it when my post gets a lot of responses. Thanks for the interesting comments and debate. TBromgard.