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max amount of work

Posted: Sun Jan 29, 2017 8:28 pm
Can someone please explain how a reversible expansion gives the max amount of work and why work for a reversible process is more negative than work for an irreversible process?

Re: max amount of work

Posted: Sun Jan 29, 2017 8:41 pm
If a process does work on the surrounding, you get more work out of the process if it is done slowly. This is because less heat is lost to the surroundings. Therefore, a reversible process, infinitely small does the maximum work. One example of a reversible process is the work done by a gas expanding against a piston.
The reversible expansion does the maximum amount of work because the gas is pushing against the maximum possible external pressure. Since the process remains at equilibrium throughout the reversible expansion, Pext = Pint. When Pext=Pint, the external pressure is at its maximum for work to be done by the system because if it was any higher, the process would reverse and the gas would be compressed.

Hope this helps!

Re: max amount of work

Posted: Sun Jan 29, 2017 9:44 pm
(Having trouble posting my own post, so I'm using this one to ask a slightly similar question--sorry for any confusion)

What is the difference between a real system and a perfect system?

Thank You!

Re: max amount of work

Posted: Tue Jan 31, 2017 10:27 am
Hello Tasmaia,

I'm a little confused on what specifically you are referring to. Could you list a page number or problem that you are confused about?

Re: max amount of work

Posted: Sun Feb 26, 2017 3:01 pm
Perfect systems would theoretically be reversible, meaning the reactions occuring within them would occur extremely slowly and with the maximum amounts of energy and work being done or used up. Real systems don't necessarily work that way.