Re: [Phys-l] two kinds of electrical charge ????????

[John Denker <jsd@av8n.com>]

On 07/31/2007 05:31 PM, Jeffrey Schnick wrote:
> I find your One Kind of Charge document intriguing. 

:-)

> Agreement with your
> position can be found in slides 5 and 6 of  Introducing Particle Physics
> by Pablo del Amo Sanchez at:
> <http://www.ep.ph.bham.ac.uk/general/outreach/Masterclass/talks2007/pdfs
> /mc2007_PPIntro_Pablo.pdf>

> which would suggest that if you are going to say that there are two
> kinds of electrical charge, then to be consistent, you better say that
> there are 6 kinds of color charge.

Yes, that would be consistent.  Consistently bad, but consistent.

I cannot imagine why anybody would /want/ to treat the left half
of the number line differently from the right half.  Just from
pedagogical considerations, the students come in perfectly happy
with a one-component model ... so why go to the trouble of beating 
it out of them, when for 250 years the math and the physics have 
said that the one-component model was fundamentally correct?

> I disagree with your characterization "... just to introduce the idea of
> 'charge' (Q), say that the amount of charge can be positive, zero, or
> negative, and proceed from there."  of the approach taken by "Reference
> 4" (The Feynman Lectures on Physics) in the document:
> <http://www.av8n.com/physics/one-kind-of-charge.htm>

OK, I now see that Feynman is not a good illustration of the
point I was trying to make.  I removed the reference just now.

> On page 12-7 of Volume I, Feynman says, "Objects carry electrical
> charges which consist simply of electrons or protons."
>
> On page 1-1 of Volume II, he says, "There are two kinds of 'matter,'
> which we can call positive and negative."
> and,
> "And all matter is a mixture of positive protons and negative electrons
> which are attracting and repelling with this great force."

As a statement about /matter/ that is mostly correct.

There's a difference between matter and charge.  It is perfectly
possible to have N different kinds of matter but only one kind
of charge.

Still, I agree that Feynman is not a good illustration of the
point I was trying to make.  I removed the reference just now.


=================================================================

I was taught the one-component model in school.  Until a couple of 
days ago, I did not even realize there *was* a two-fluid model.  
No kidding.

I've read lots of physics texts, and I must have always skipped
over the part about the two-fluid model.  Recently I've gone back 
and spot-checked a few texts, and some of them do in fact advocate 
the two-fluid model.  Most of them say only a few words about it, 
so wouldn't be hard for me to skim right over it.  Also, as soon 
as they start writing down equations they write one-component 
equations, so it would be easy to conclude they weren't serious 
about the two-fluid model.  I don't mind if somebody briefly
uses it as a figure of speech, so long as they don't take it
seriously, and immediately segue into a one-component theory
and thereafter talk about "the" charge.

But when somebody starts arguing that the two-fluid model is 
"right" and the one-component model is "wrong", I just cannot
imagine where that is coming from.

> On 07/31/2007 06:34 PM, Larry Smith wrote:

> > Randy Knight's "Physics for Scientists and Engineers: A Strategic Approach"
> > does make the assertion (on page 786) that "there are two and only two
> > kinds of charge" which conclusion is arrived at by simple experiments.  He
> > does add at the bottom of the page that "while the charge model is
> > consistent with the observations, it is by no means proved.  One could
> > easily imagine other hypotheses that are just as consistent with the
> > limited observations we have made so far."

1) Thanks for checking.

2) The second part -- the disclaimer -- counts for a lot.  It 
is absolutely true that simple experiments are /consistent/ with
the two-fluid model.  I question whether it is good pedagogical 
procedure to lead students down the two-fluid blind alley, but 
I can't really complain.  And as long as the students understand
that the experiments are also consistent with other models, 
presenting weakly-consistent theories is not bad, and may
even be good.

I just wonder whether the students are skillful enough to 
remember which theories they have been exposed to are well
established, and which are only weakly /consistent/ with a
handful of observations.  Being a scientist requires being
able to keep track of such distinctions.  I wonder if there
is any follow-through on this, such as offering good and/or
bad competing theories and quizzing the students on the
status of each.  I suspect they wouldn't do very well on
the first such quiz.

After all, it's apparent that many textbook authors have no
clue about how poorly-supported the two-fluid model is.  It
hardly seems fair to expect the students to be smarter than
the textbook authors.