Re: definitions of heat

[Jim Green <JMGreen@SISNA.COM>]

> John Denker is the high priest of those who believe that the word heat
> can be used in many ways and that the context will allow whoever wants
> to understand you to understand you.

Well, Brian, there are those of us who hold John in high esteem but hardly
as our "high priest" -- sorry John.  And we agree that one may define any
word pretty much any way one wishes -- while still being understood by
one's conversant.

The problem is not in the _definition_ but in consistency.  Some of us look
to the First Law and ask what then is "q".  You want to say that "q" and
"q" are the stream and the rain below -- But these are things that
"flow".  Some of us have found that this image is very
counter-productive.  They end up thinking that "q" (and maybe "w") are
fluid-like and are "added" to the system and then they are "inside" the
system.  Traditionally the students confuse "q" with internal energy (and,
no, energy does not flow either)

Fynnman's (sp?) blocks are currently more often used with the same effect.

But it should be made clear to the students that "q" and "w" are DONE to
the system - We can discuss just what to call them -- but they are
ACTIONS.

And for some of us who regard the Second Law with some value, we note that
"q" is _work_ which _may_ be due to a temperature difference, but need not
be.

> .......  Zemansky's text, Heat and Thermodynamics, described by
> Herbert Callen as "the classical introductory text in English" was
> first published in 1951, half a century ago.

While these brethren made some valuable contributions, if one wishes to
promote the same picture, one really should go back to Aristotle or before
-- to those who started this mess.

> So that's where I and, I think, many of us stand.  For clarity and
> precision and for enhanced student understanding we certainly do want
> to restrict the use of the word - as the majority of texts over the
> last 50 years have.

Brian, for some of us, "for clarity and precision" we think that the
picture should be _correct_ rather than convenient.  This seems to be best
done by never using the word "heat" -- otherwise one ends up in the world
of cartoon physics.

A postscript: does the list note that, in many of our discussions, a
suggesting is given and then many of the most loquacious spent a great deal
of time defending their then current views -- their own status-quo.  It
seems as if they we saying something like "Hey these have been my views
since HS or this is the way I have given my lecture for many years and I am
not going to change now."  It is as if the suggestion were a personal
attack on them.  Rumford (and many others) met this problem, tried
diligently, and, alas, lost.

We do not often hear a comment like "Oh, I have never thought of that, I
will think this through and maybe adopt this view."

Here we have the editor of AJP coming out and stating the problem clearly
-- and we stil won't stop to consider the value of a clearer picture.

Too bad.



Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen