Re: Joule Experiment

[Larry Sacks <lsacks@pcs.cnu.edu>]

	Classical experiment, yes; "mechanical equivalwent of heat, no.  
This was one of many misinterpretations of classical experiments used to 
establish the current approach to thermo.  The work done was converted to 
the internal energy of the worked fluid (water, here, ice-water in 
others).  To say that "heat" was involved confuses the issue, for if w = 
-q, then delta U = 0 and the temperature would not have changed.  The 
"heat" of the experiment could only be the error part due to exchange 
with the surroundings.

	Does the entropy change?  Of what?  Of the water?  I guess so.  
Of the entire system (source of work, paddles, water etc.) - I guess it 
would have to, since there is an actual process occurring (spontaneity = 
increase in S).  It shouldn't matter what the working fluid is.  And it 
shouldn't matter how the work is accomplished - whether by stirring or 
"squishing".  

	Please note that I have attempted to help out without even 
introducing further discussion about "heat" as a noun or verb.  You're 
welcome.

	Larry

On Tue, 15 Oct 1996, Jim Green wrote:

> I have been thinking about the (several) Joule mechanical-equivalent-of-heat
> experiments.  Joule seems to have used a container of water with a few flat
> brass paddles which were rotated on a vertical shaft to stir and
> consequently heat the water.
>
> Does the Entropy increase during this experiment???
>
> Would the Entropy increase if this were done with an ideal gas as the fluid?
>
> If this gas were sqished with a piston instead, would the Entropy increase?
>
> Somebody please help me ot here.
>
> JMGreen@sisna.com