Re: Energy, etc (fwd)

[Leigh Palmer <palmer@SFU.CA>]

> At 10:17 AM 8/10/99 +0100, you wrote:
> > I agree with Jim. What about the "magnitude of energy" instead
> > of "level of energy"?  Yes, to say "the amount of energy" is a
> > trap promoting the "substance-like" interpretations.
>
> Yes, I think that "magnitude" is better.   Any language which can be
> construed as referring to a substance is evil, wicked, bad, and nasty --
> and just bad pedagogy -- at least.

I have a problem or two with "magnitude". The term is usually
associated with vector quantities, though it is itself a scalar,
a minor drawback, but it also implies the existence of some sort
of canonically mandated zero of energy when what we really want
the students to concentrate on is energy differences. There is,
of course, a natural zero for energy, but we wouldn't want our
students adding in the mc^2 terms in a roller coaster problem,
would we?

Why can't we say "the energy" and define it somewhere else? That
is what we do with the entropy (which also has a natural zero)
when we teach them about it.

A student's introduction to these quantities should be as
symmetrical as Clausius perceived it to be:

Energy is a function of the parameters which define the state
of a system. It is measured relative to a conventional zero.

Entropy is a function of the parameters which define the state
of a system. It is measured relative to a standard entropy.

Leigh