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Re: Who is the Authority?



Van E. Neie says:

Pardon my innocence, but if such "giants" in the field as Zemansky
and Sears and other well-known authors have consistently gotten it wrong,
why did it happen, and who are the authorities who decide that they are
wrong? This is not a sarcastic question, it is quite serious. Jim and
Leigh have consistently and persistently stated that virtually all of us
get it wrong, so they must have some authoratative source that "gets it
right."

I would like to see the passage on which you base your claim,
Van. If I said that I certainly did not intend to do so, but
I don't believe I did, so I won't apologize.

I certainly am aware that most all authors of texts, since they
cannot be authorites on all subjects, will get some things wrong or choose
to adopt an approach that doesn't fit into the mainstream of physics
thinking. However, if the authors are flat wrong (as has been suggested),
this means that the myriad of text reviewers are equally ignorant and it
begs the question, "How did so many of us get it screwed up?" and more
importantly, "What jury came to that verdict?"

If Zemansky's text on Thermodynamics (as I remember one contributor quoting)
says that "heat is energy in transit" (or something to that effect), then
that grammatically classifies heat as a noun and Jim is vehemently stating
that heat is a verb! It makes me wonder how many other errors are in
Zemansky's text?

There is absolutely no doubt that heat is a verb. It is also a
noun. Therein lies a potential cognitive trap which I have no
trouble avoiding myself, but which I wish to guide students
around. It has been my experience that if they are unguided
*most* students will founder in that trap and I believe they
can only very rarely recover if left in it long, and they will
not recover at all without help (which can come from reading,
of course, as well as proper instruction).

Finally, a question that I still want an answer to: If heat is work and
heat is a verb, then can I say, rather than heat an object, I can work it?

First let me correct your misunderstanding. Heat is not work.
That premise does not seem to be necessary for your question
to be well formed, however. You ask if you can work an object:

Yes, you certainly can. It will "heat up" in colloquial
vernacular in some cases (e.g. an inelastically flexed piece
of metal, perversely called "cold-working" the metal) and it
will not in others (e.g. elastic compression of a spring).
In both cases you will raise its internal energy by an amount
equal to the amount you work it, whether it "heats up" or not.

Try flexing a paper clip rapidly until it breaks. quickly
touch the broken ends to your lips. Stretchb an elastic band
quickly and touch it to your lips in the stetched condition.
Let it cool to ambient temperature and let it relax quickly.
Immediately tough it to your lips again.

Now of course I know that you already know this. I made the
answer in the form I use when communicating with my entire
class by means of a maillist I have to answer student
questions. You now have your answer. Does it satisfy you?

And my original question: "What does it mean to heat something?" It
certainly can't mean "apply heat to it," because that brings us back to the
caloric language, doesn't it?

Yes. It means "apply a hotter object to it". You are
correct when you avoid "apply heat to it".

To heat something means to place it in thermal contact with
a system at a higher temperature. The amount of energy
transferred from one system to another in this process is
called the heat (noun) associated with the process and is
usually designated "Q".

And what about thermal energy? It seems to
be another of Peck's Bad Boys. If I can't apply "thermal" to energy, is
there anything I CAN apply it to? Has it become a useless term?

Yes. It is a useless term, but worse than that. Because it
does not have a precise meaning it is confusing to students.

Leigh