Re: Comments: txtbk misconceptions

["Rauber, Joel Phys" <RAUBERJ@mg.sdstate.edu>]

I may be about to be argueing semantics, but here goes; of course that was 
my point.

> > Some of the later items strike me as being more of the nature of
> > disagreement concerning terminology and aren't misconceptions.
> >
> > item 36 is an example of this.
> >
> >  36) 2-plate capacitors are charged with energy, not with electrical
> >      charge. A charged capacitor contains just as many + and - charged
> >      particles as a discharged capacitor.
> >
> > I don't think it is a misconception to say 2-plate capacitors are 
"charged
> > with electrical charge", the books I read that say this or similar
> > statements; provide an operational definition of what those words mean
> which
> > is similar to the second sentence above.  And hence doesn't represent a
> > misconception.  At worse its a poor choice of words (not my opinion 
though,
> > I like the words just fine); and therefore not a proper item for this 
list.

> I disagree on this one. The charged two-plate capacitor does indeed have
> just the same total charge (zero) as an uncharged one. The Q in C = Q/V is
> the magnitude of the charge on one plate, not the total charge.

I never said otherwise, let me rephrase, the books are generally careful to 
specify that "charging up a capacitor to charge Q", is really putting equal 
and opposite net charge on each of the two conductors.  This is exactly what 
you say above.  Therefore I don't think those words are a misconception, 
when they are operationally defined to mean the correct situation.

> One way to
> charge such a capacitor is to move charge of one sign from one plate to
> the other, thereby changing the energy of that configuration of charge.
> The usual textbook explanations generally don't get across to students
> what's actually happening.

The fact that it doesn't get across to the students doesn't mean that its a 
misconception; it just means that it may not be a vary good way of getting 
the conception across to the students.  That is a different issue.  (also, 
might mean the students really don't know how to read, but that is also 
another issue).

A book propagated misconception, IMHO, is not a poor choice of words that 
doesn't get the point across; rather it is the use of the wrong physical 
principle to explain something.

I'm trying to seperate poor pedagogy from outright wrong physics being 
propagated.  Therefore, I still standby what I said about item 36.

We may have to agree on what a "misconception" is, in order to generate this 
list.

Joel