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Re: Thermal Energy - thermalization of rotational energy



On Thu, 7 Mar 2002, Jim Green wrote:

Well, John, firstly I would normally think of large amplitude macroscopic
system vibrational motion as essentially translational.

Then perhaps I could ask, what about "small amplitude macroscopic
vibrations"? Or what about simply "small amplitude vibrations"?
That is, at what point, if any, do you start to consider
"vibrations" to be internal energy?

And secondly I would not put "bulk rotational kinetic energy and large
amplitude macroscopic system vibrations" _anywhere_ in a thermo problem --
they just don't obtain in my thermo world.

I *tend* to agree which is why I like to distinguish them from
more clearly thermal forms of energy, but I can make up perfectly
good, if unusual thermo problems that do include these forms of
energy on the deltaE side of the first law.

Now finally would someone please tell me what is meant by "thermal energy"
and "thermalize"

O.K. I'll take a shot.

Thermal energy is thermalized internal energy.

To thermalize means to allow subsystems to interact for a long
enough time so that the energy they have is distributed according
to the Boltzmann distribution or, when necessary, its quantum
mechanical counterparts.

Caveats: As I have said before I find the concept of thermal
energy useful even if I am a bit wary of it. And while I think
I'm likely to stick with my definition of "thermal energy," I am
open to improvement on my definition of "thermalize."

John Mallinckrodt mailto:ajm@csupomona.edu
Cal Poly Pomona http://www.csupomona.edu/~ajm