Re: A "heat" question

["Frohne, Vickie" <VFrohne@BEN.EDU>]

         In teaching physics, there is always a trade-off between being
strictly correct and being comprehensible. The operational defnitions of
"heat" and "internal energy" given below enable the students to
conceptualize the phenomena. Visualizing energy as "something" being
transferred helps them solve the problems.   IMHO, explanations of why these
definitions are not strictly correct can wait for a more advanced course.  I
have enough trouble just getting the students to understand that "heat" and
"temperature" are not the same thing.

Vickie


-----Original Message-----
From: John S. Denker [mailto:jsd@MONMOUTH.COM]
Sent: Tuesday, November 26, 2002 5:49 PM
To: PHYS-L@lists.nau.edu
Subject: Re: A "heat" question


Frohne, Vickie wrote:

> Hewitt, in the "Conceptual Physics" books, distinguishes between
> "heat" and "internal energy" very nicely. "Heat" is energy in motion,
> i.e. energy that is in the act of being transferred.

I assume this was meant to say not just any energy,
but energy that is being transferred in thermal form.
Surely the heat-is-a-verb partisans don't think that
simple macroscopic F dot dx energy transfer is "heat".

Unfortunately, no matter how carefully heat-is-transfer
idea is expressed, it remains a Bad Idea.

It is occasionally true but _not generally true_ that
energy in motion can be divided into a purely thermal
piece and a purely nonthermal piece.  It has been known
for over 200 years that thermal energy is not conserved
separately from other forms of energy.

People who fall victim to the thermal-transfer-of-energy
idea pay the price when it comes time to analyze a
dissipative transfer, such as the venerable cannon-boring
experiment.

Note that I don't care what you call thermal-tranfer-
of-energy.  You can call it h&@t or whatever.  It's
a Bad Idea, no matter what name you give it.  For
details, see
   http://www.monmouth.com/~jsd/physics/thermo-laws.htm

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Thompson or Count Rumford.

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