reversible heat and irreversible weight-lifting

[John Denker <jsd@MONMOUTH.COM>]

At 10:19 AM 10/31/99 -0800, John Mallinckrodt wrote:
>
[certain]
> processes in the real world are almost without exception irreversible and
> cannot be used to calculate the change in entropy ...
> In any event, the heat we are
> talking about here is *always* a quasistatic exchange of energy between
> two systems that occurs specifically as a result of an infinitesimal
> difference in temperature.

And in this context at 04:04 PM 10/31/99 -0800, John Mallinckrodt wrote:
> Sheesh.  Why *is* it *so* hard for you simply to acknowledge the point of
> what I am saying?

That's because several of the things JM is saying are closer to being
diametrically wrong than they are to being correct.

In the real world, irreversible processes are precisely the ones that
*must* be considered when calculating the change in entropy.

In the real world, many forms of heating are irreversible.  In contrast,
restricting the definition of JM-heat to quasistatic quasi-isothermal heat
flows guarantees that JM-heating is reversible.

At 04:04 PM 10/31/99 -0800, John Mallinckrodt wrote:
> Look.  If *you* haul a weight from height H = 1m to H = 2m in the real
> world *you* have just performed an irreversible process for a number of
> reasons.

So in a single day we are told that the important thing about JM-heating is
its reversibility, and the important thing about weight-lifting is its
irreversibility!??!?!!???

______________________________________________________________
copyright (C) 1999 John S. Denker             jsd@monmouth.com