# Which fundamental reversible thermodynamic process has maximum work associated with it?

By fundamental I mean isothermal, adiabatic, or isobaric. My book says that in expansion the maximum work is associated with isothermal process. But if I observe the PV graph, I feel like the isobaric work done is maximum, since it has more area under its curve. Does it depend whether ΔV is constant or the supply of heat is constant. Also does it matter if the system is being compressed or expanded, A theoritical reasoning might be better than just a numerical example.

• Is this from a book of physics problems? If so, you should keep in mind that most (all?) of those books have incorrect solutions and poorly worded, ambiguously worded questions. This might be one of them. But you should tell us the exact wording of the question. – garyp Apr 22 '18 at 16:00
• @garyp It's not from a question but rather in theory, the book says: "The work done by the system alwayas depends upon the external pressure. The higher the valye of Pex, the more the work done by the gas. As in expansion, Pex cannot be more than Pgas. Under this condition, the work done in reversible expansion is maximum. On the other hand, the work involved in the intermediate compression process is larger than that involved in the reversible compression. Conserquently, more heat will be released in the case of intermediate compression.", by intermediate comp. it means irreversible work. – user45838 Apr 22 '18 at 16:08
• Thanks. The wording is a little hard to follow. There's probably a larger context that I'm not seeing. But where does it say that the isothermal curve is associated with maximum work? – garyp Apr 22 '18 at 16:14
• @garyp It further said that in isothermal process all the heat is transferred only to the work since temperature of the system is not increased. While in case of isobaric process the heat is transferred to do work as well as to increase the temperature. and so less work would be done here. The graph isn't drawn in the specific context of this paragraph but rather to show the different processes. I related the graph and and the paragraph andfigured that isobaric work is more here but the logic given in the book doesn't seem to have any flaw too. Can you clearify it. – user45838 Apr 22 '18 at 16:25
• Simultaneous posts! Yes. that's it. – garyp Apr 22 '18 at 16:37