Reversible Processes

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Miriam Restrepo 2D
Posts: 1
Joined: Fri Sep 26, 2014 2:02 pm

Reversible Processes

Postby Miriam Restrepo 2D » Sun Jan 25, 2015 10:10 pm

How is P external kept equal to P for a reversible process?

martha-1I
Posts: 76
Joined: Fri Sep 26, 2014 2:02 pm

Re: Reversible Processes

Postby martha-1I » Sun Jan 25, 2015 10:57 pm

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.
Last edited by martha-1I on Sun Jan 25, 2015 11:58 pm, edited 1 time in total.

Niharika Reddy 1D
Posts: 127
Joined: Fri Sep 26, 2014 2:02 pm

Re: Reversible Processes

Postby Niharika Reddy 1D » Sun Jan 25, 2015 11:51 pm

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)

martha-1I
Posts: 76
Joined: Fri Sep 26, 2014 2:02 pm

Re: Reversible Processes

Postby martha-1I » Sun Jan 25, 2015 11:57 pm

oh yes I did. Sorry about that. I will go back and edit it. Thank you!

Justin Le 2I
Posts: 142
Joined: Fri Sep 26, 2014 2:02 pm

Re: Reversible Processes

Postby Justin Le 2I » Wed Jan 28, 2015 12:11 am

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.


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