Query on Isentropic relationships (such as PV^gamma = constant)

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The discussion centers on the application of the isentropic relationship PV^gamma = constant, which is derived under the assumption of quasi-equilibrium or reversible processes. It is clarified that this relationship should only apply to isentropic processes, which are both adiabatic and reversible, rather than to all adiabatic processes. Participants express concern over online resources that use the isentropic equation for adiabatic processes without emphasizing the need for reversibility. The consensus is that the term "isentropic" inherently indicates constant entropy, thus implying reversibility. Misinterpretations in educational materials may lead to confusion regarding the conditions under which PV^gamma applies.
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Hi all, I have a question. So from the derivation of the Isentropic process relationship PV^gamma = constant, there is a step dW = PdV, which can only be said for quasi-equilibrium (or reversible) processes. As such I believe PV^gamma = constant (and the family of equations) should not be applicable to just adiabatic processes? Ie, it should be applicable only for adiabatic + reversible = isentropic processes?

However, I've seen couple of online notes/books, and http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/adiab.html#c3 case in point, using PV^gamma = constant for adiabatic process. My suspicion in that in these sources, when they say adiabatic, they really mean isentropic?

Thanks. Also, not sure if this is the right area to post this but yea...
 
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You are correct, it does not apply to adiabatic, irreversible processes. But that's kind built right into the word itself: isentropic. That implies the process must be constant-entropy, i.e., reversible.

I don't immediately know why the site you link is using it without specifying the reversibility condition.
 
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