Re: [Phys-L] irreversible quasistatic

[Carl Mungan <mungan@usna.edu>]

> > I will draw two identical cycles (in the sense of having the same
> > vertices and connecting curves). Cycle A will consist purely of
> > reversible processes. Cycle B will consist of at least one
> > irreversible quasistatic process;
>
> Those three sentences are incompatible.  Pick any two.
>
> That is to say, cycle A and cycle B should look different on any
> reasonable "indicator diagram".  If not, some key variable is being
> left out, and the diagram is not a meaningful representation of the
> system.

Okay let me try again. This time I’m going to consider an isochoric process. One mole of monatomic ideal gas is held in a fixed volume hollow metal sphere. For process B, transfer thermal energy irreversibly but quasistatically to the gas using my “swinging pendulum ball” method. (Unlike the J-T plug, the gas now does not split into “parts” during the process.) Say the gas warms up from 300 to 400 K For process A, same starting and ending points but this time we do a reversible heating, by bringing an infinite succession of water baths with temperatures T incrementing from 300 to 400 K in dT steps into contact with the gas.

Both curves A and B look like identical vertical line segments. This time I don’t see any flaw in my reasoning. Where’s the incompatibility?

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Carl E. Mungan, Professor of Physics  410-293-6680 (O) -3729 (F)
Naval Academy Stop 9c, 572C Holloway Rd, Annapolis MD 21402-1363 
mailto:mungan@usna.edu <mailto:mungan@usna.edu>     http://usna.edu/Users/physics/mungan/ <http://usna.edu/Users/physics/mungan/>