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But what is wrong with starting with a model like this and observing
that it does not agree with experiment, thus requiring a better model
to replace it? Even using the Fermi speed instead of the mean speed
of the electrons doesn't give the correct result, a further correction
of the mean free path by Einstein being needed - hastily following
the discussion by Thornton and Rex on p. 324. Isn't this something
like the constructivist's approach -- replacing models with more
viable models? We never got to this chapter, and I don't think
technology students and their instructors would be interested in this
kind of theory. Perhaps they should be.
AnotherI hope you weren't referring to my battery example. I was only trying to
related misconception is that the electron which emerges from
one end of a wire carrying a current is not the same electron
as the one that goes in at the other end, delayed only by
lightspeed. There is no way to tell any electron from any
other electron, and in a sense the statement is meaningless.
I never have understood why these factoids are inserted into
curricula.
explain in simplistic technician language what the direction of electron
current in the external circuit of a battery would be if the charge sign
convention were reversed. I haven't had much occasion to teach about
metallic conduction in recent years, but when I taught AP Physics and
E&M, I recall calculating the drift velocity of electrons in metallic
conductors on the basis of the Drude model - a standard problem in
general physics texts as I recall. It was a snail's pace compared with
lightspeed. I wouldn't think of saying that one could track a single
electron in going from one terminal of a battery to the other in the
external circuit. But the students wouldn't know that fermions were
indistinguishable at the general physics level.
Perhaps my comments are naive, but this discussion list keeps me on my
toes.
I got my lawn cut, and I think I've improved the high voltageI keep my computer running 24 hours a day, because a virus or something
arcing behaviour of my monitor. Not a bad day.
makes it take many tries for it to detect both of my hard disk drives.
Someday I will get an expert to look at it.