Re: [Phys-l] T dS versus dQ

[John Denker <jsd@av8n.com>]

On 01/12/2010 04:28 PM, Bob Sciamanda wrote:
> > then E is not a function of state during the time that
> > the piston is provoking sound waves, shocks, et cetera
> > in the fluid.  The analysis crashes and burns at this
> > point.  We cannot proceed in this direction
>
> Certainly (Duuuh!)!  

OK.

> The equations of state apply only to 
> definable.EQUILIBRIUM STATES, 

I do not accept the restriction to "EQUILIBRIUM" states;
see below.

> where the state variables are definable.  

We agree that the needed variables should be definable.

> If 
> you want to apply equilibrium thermodynamics 

But what if I don't want that?  What if I don't want to
be restricted to equilibrium situations only?

> to the PROCESS, then choose a 
> reversible process which connects the initial and final states with an 
> infinite series of equilibrium states.
>
> This is much ado about nothing.

If you restrict attention strictly to equilibrium situations
and reversible processes, then all of thermodynamics becomes
much ado about nothing.

I do not accept such a restriction.

Even something as central and basic as the Carnot heat engine
requires two heat baths, at temperature T1 and temperature T2.
Each heat bath is in equilibrium with itself ... but not with
the other.

We all know how to handle this situation.  I'm just saying
we shouldn't pretend it's an equilibrium situation.  Any
nontrivial thermodynamics is non-equilibrium thermodynamics.

Also: In recent days several people have put forth perfectly
well-posed scenarios involving irreversible processes.  Any
serious theory of thermodynamics must be able to handle
these scenarios.  In fact we know perfectly well what
happens in these situations; we can quantify the energy
and entropy and temperature.  There's nothing wrong with
the physics;  there is only a problem with the archaic
terminology and misbegotten concepts that we use to _model_ 
the physics.