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Reversible Processes

Posted: Sun Jan 25, 2015 10:10 pm
by Miriam Restrepo 2D
How is P external kept equal to P for a reversible process?

Re: Reversible Processes

Posted: Sun Jan 25, 2015 10:57 pm
by martha-1I
if you're referring to when we want to find work, then you are using the wrong equation for the reversible process. You are thinking of the equation for the irreversible process which is w=-PexV. For reversible processes, we use w=-nRTln(v2/v1) since we are assuming that all heat lost is converted into work.

Re: Reversible Processes

Posted: Sun Jan 25, 2015 11:51 pm
by Niharika Reddy 1D
I think Martha may've switched the order of the initial and final volumes around in the equation for the work of a reversible process. It should be V2/V1, or Vfinal/Vinitial; wreversible=-nRTln(Vfinal/Vinitial)

Re: Reversible Processes

Posted: Sun Jan 25, 2015 11:57 pm
by martha-1I
oh yes I did. Sorry about that. I will go back and edit it. Thank you!

Re: Reversible Processes

Posted: Wed Jan 28, 2015 12:11 am
by Justin Le 2I
Figure 7.16 on page 249 has a good visualization of the difference between reversible and irreversible processes. Note that the pressure in the reversible graph is not constant whereas the pressure in the irreversible graph is constant.