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Re: CONSERVATION OF ENERGY



On July 22, 1997 John Mallinckrodt <ajmallinckro@CSUPomona.Edu>
comments on:
I suspect that John M. would refer to the temperature increase of food
in the microwave oven as warming rather than heating. Would the Martian
word gamming be acceptable?

Well, I think I'd call it "warming due to heat" as opposed to "warming
due to work." I don't intend "warming" to refer to some "third kind" of
thermodynamic process, it simply means the internal energy has increased
and rethermalized.

The internal energy has increased at the expense of the entering electric
energy, and the system is thermalized. No heating and no working is done
on the system.

I am not very comfortable with this new concept of warming as applied to
our sliding-cube situation. The initial kinetic energy (inside the system)
is converted into dU. I am referring to this process as warming only when
the system boundary includes both pieces of iron. But suppose I decided
to describe what I see in terms of two interacting systems, each with its
own boundary. In this case the dUa of the cube could be said to be due to
'working it' (net frictional force multiplied by the sliding distance).

And part of dU, dUb, is due to 'heating it'. The flow of heat exists because
atoms near the sliding surface, in the cube, are more agitated than atoms
near the sliding surface in the base. If the concept of temperature were
applicable we would say that T1 (cube layer) is higher than T2 (base layer).
Why? Because the affected area in the base is larger than in the cube and
local concentrations of internal energies are different.

How can a change of internal energy be called warming in one kind of
consideration and heating or working in another?

How meaningful is the term heat when dT, which would be responsible for
it, can not be defined? I guess the term warming was invented for that
kind of situations. Why do you say, John, that warming should not be
seen a 'third process'?

The intuition tells me that there is something peculiar in dissipating
situations; I can not find words for describing them macroscopically.
Numerical problems on warming, worded in terms of what we teach in an
introductory physics course, would be helpful to clarify the issue.

Ludwik Kowalski