Re: electric charge

[Ludwik Kowalski <kowalskiL@MAIL.MONTCLAIR.EDU>]

Larry Cartwright wrote:

> William Beaty wrote:
> > I've encountered people who think that electric current is "real", and
> > that electric charge is just an abstract concept.   Very weird.  (The flow
> > rate of a substance is more real than the substance which flows?!!!)
>
> I'm probably getting in over my head here, (and I'm praying that someone
> more highly informed and articulate will snatch up my banner and carry
> it victorious to the finish line) but I am compelled to object to the
> 19th century characterization of electrical charge as a "substance".  Is
> not electrical charge a *property* of the elementary particles which
> make up what we call substance, the quarks and leptons and bosons, etc?
> To me, calling charge a substance is like insisting that blue is a
> substance, or foul-smelling is a substance or strangeness is a
> substance.  How have I erred in my conceptualization of the sub-atomic
> structure of the Universe?

JohnD's answer was very good. Let me ask an additional
question and add a comment. Yes, charge and mass are
properties (attributes) of matter. But saying this is not
sufficient to identify the attributes.

1) Charge is the attribute resulting in (responsible for) attraction
and repulsion according to Coulomb's law. But why should
this particular law be used to make the attribute distinguishable?
Why not, for example, F=B*I*L law, or the electrolysis law, etc.?

In my opinion the law in which the attribute is first encountered
by students should be used to define it. I know that teachers
can invent many pedagogically acceptable sequences. But the
most common sequences start with electrostatics. As long as
this is the case Coulomb's law is the best choice. For that
reason I would prefer ampere to be defined in terms of coulomb
and not the other way around, as in SI. There is something anti-
pedagogical in using C before A. Does anybody know an
introductory physics textbook (not a technical manual) in
which the sequence of learning new concepts begins with two
long straight wires attracting each other? As I argued in 1986,

<http://alpha.montclair.edu/~kowalskiL/SI_1986.html>

the SI is far from being an ideal pedagogical sequence. I am
always unhappy when it comes to epsilon_o and mu_o, or
when I tell students to wait for the definition of ampere
when coulomb is already used.
Ludwik Kowalski