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Re: ENERGY WITH Q



At 09:54 AM 10/28/01 -0700, John Mallinckrodt wrote:
Any energy change in a system that is associated exclusively with
an alteration in the occupation numbers (rather than the energy
levels) of the allowed quantum states *will* alter the entropy
of the system and ought, therefore, to be considered "heat."

Any energy change in a system that is associated exclusively with
an alteration in the energy levels (rather than the occupation
numbers) of the allowed quantum states will *not* alter the entropy
of the system and ought, therefore, to be considered "work."

I'm obviously not understanding something here. Perhaps an example will
illustrate my difficulty.

1) Start with a cold stationary flywheel. Warm it up.
1a) Does the warm-up process count as heat?
1b) How do we describe it in terms of energy levels and occupation numbers?

2) Again start with a cold stationary flywheel. Start it spinning.
2a) Does the spin-up process count as work?
2b) How do we describe it in terms of energy levels and occupation numbers?

3) What is the difference between (1b) and (2b)? Can we connect this
difference to heat versus work using the recipe JM suggested?

I think all the answers are easy until we get to item (3). It seems to me
that (2b) is altogether too similar to (1b) -- a change in occupation
numbers with no significant change in the nature of the levels being occupied.