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Pop Quiz!!!

What is the (average) speed of free electrons in a copper speaker wire during typical music playback?

A. Speed of light in vacuum
B. About 90% of speed of light in vacuum
C. About 1% of speed of light in vacuum
D. A few mm per second
E. None of the above

[This is not a joke, so be serious.]

I'll take a stab at it. How bout C.

I'll go with b.

I'd go with E. The drift velocity of electrons in a copper conductor is about 1/3 of a mm per secoond. In an AC current the average drift would be zero.

Are we bi-amping?
Does the line run uphill or downhill?
Would it be the same as my cold water pipes?




"be serious" ........oh sorry missed that

Masa, you didn't specify, but you may be aiming at the drift velocity of the electrons in the wire(a few mm per second)rather than the Fermi velocity of the electrons. If this is the case, I'd like to know why I can't flip the light switch and jump into bed before it gets dark. Any true audiophile reading your question may also be puzzled as to why you didn't specify "cheap" copper or "6 nines".

The electrons dont start at one end and flow to the other like water in a hose!!!! That is why you cannot hit the switch and then jump in the bed...

I did have a physics prof that always said you could run between the drops in the rain. He was committed (seriously) later in life though!!

Okay... the answer is D.

The instantaneous speed of random movements of free electrons in copper (Fermi velocity) is about 1% of speed of light. However, the "net flow" of electrons (drift velocity) that makes up the electrical current is a few mm per second, assuming the amp output of about 1 ampere and a "usual" cross-section of speaker wire.

Then, the electromagnetic field (i.e., electrical "signal") transmits through copper at about 90% of speed of light. And this is why you "can't flip the light switch and jump into bed before it gets dark."

Of course, if you use the Kimbar Kable instead of the Home Depot lampcord, the Fermi velocity will magically increase at leaset 10 fold. Oh, and don't forget that after a proper cable break-in, it will further increase by 2 fold because electrons can now travel more smoothly.

Seriously, the "pre-filled water hose" analogy is correct: when you open the spout at one end of a long hose, water starts to flow out at the other end of the hose IMMEDIATELY, even though the actual speed at which water flows inside the hose is fairly slow. In this case, the speed of water flow is equivalent to drift velocity of electrons, yet the "information" that the spout has been opened (pressure wave) transmits through the hose at the speed of sound.

Now, is that the speed of sound through water, or the speed of sound through air?

Actually,

I think it is speed in a vaccuum!!!!

Dirtdevil or Hoover??