Re: felt dismissed

[William Beaty <billb@ESKIMO.COM>]

On Sat, 8 Jun 2002, Hugh Haskell wrote:

> Good point, Bill. I know that when talking about it, I do take care
> to always talk about the "free electrons"  in a conductor, but I'm
> not sure that I have been as explicit as perhaps I should have been
> in emphasizing that point. I guess that I just never thought about it
> as a student misconception. It would appear that I was wrong. I will
> be more careful about that in the future.

Actually this was just in the March issue of AJP (the one on Quantum
Mechanics.)  IIRC some researchers found that students weren't able to
predict the brightness of bulbs in a simple circuit.  During interviews
they discovered that the students were imagining the metal atoms to be
individually neutral, and imagining that an applied P.D. was required in
order to "knock off" the electrons.  I think this all happened AFTER
students had completed the class.  The authors thought that the students'
spontaneous reasoning was interfering with the learning process.   Me, I
don't think there's anything "spontaneous" about it.  I was taught the
same misconceptions during K-12.

I think the central misconception is this:  all atoms in the everyday
world are neutral.

Unfortunately, conductivity is caused by non-neutral particles, so a
person who believes that atoms are neutral would also be unaware of the
presence of ions in electrolytes or electron-seas within metals.  They
would imagine that all substances are nonconductors, and then have to
search for an alternate explanation for currents in a metal.



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