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*From*: John Mallinckrodt <ajm@csupomona.edu>*Date*: Fri, 22 Jan 2010 15:56:07 -0800

Biran Whatcott wrote:

If one specifies a straight line on such a PV graph, then the curve

describing the pressure volume and temperature change during its

compression will necessarily cut some isotherm (actually many of them)

TWICE.

Not so. Not in the case of an isobaric or isochoric process or, for that matter, many other processes. Consider, for instance, any process for which P(V) = P_o + C (V - V_o) with C a positive constant. In fact, depending on starting and ending volumes, many processes with negative C also satisfy the requirement. All of these processes can be carried out reversibly.

The implication (for me) is that this straight line is not a description

of a reversible adiabatic. process.

That's *certainly* true, but you don't need to and, in fact, can't deduce that result from any of the foregoing observations. A reversible adiabatic process is described by a curved line on a PV graph, period.

John Mallinckrodt

Cal Poly Pomona

**Follow-Ups**:**Re: [Phys-l] PV question***From:*Philip Keller <PKeller@holmdelschools.org>

**Re: [Phys-l] PV question***From:*Brian Whatcott <betwys1@sbcglobal.net>

**References**:**Re: [Phys-l] PV question***From:*Carl Mungan <mungan@usna.edu>

**Re: [Phys-l] PV question***From:*Brian Whatcott <betwys1@sbcglobal.net>

**Re: [Phys-l] PV question***From:*John Mallinckrodt <ajm@csupomona.edu>

**Re: [Phys-l] PV question***From:*Brian Whatcott <betwys1@sbcglobal.net>

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