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### Reversible Expansion

Posted: Sun Feb 10, 2019 9:17 pm
I understand mathematically and graphically why a reversible expansion does more work, but does gas undergoing irreversible expansion ends up with more internal energy because it does less work?

### Re: Reversible Expansion

Posted: Sun Feb 10, 2019 9:26 pm
It depends on the system at hand. If the system is isolated, heat cannot come into the reversible expansion and replace the additional energy loss, so the first law of thermodynamics tells us that in the case that both systems (reversible and irreversible) are isolated, the irreversible one would indeed have less internal energy (based off of U=q+w).

### Re: Reversible Expansion

Posted: Sun Feb 10, 2019 10:18 pm
Te Jung Yang 4K wrote:It depends on the system at hand. If the system is isolated, heat cannot come into the reversible expansion and replace the additional energy loss, so the first law of thermodynamics tells us that in the case that both systems (reversible and irreversible) are isolated, the irreversible one would indeed have less internal energy (based off of U=q+w).

Where does the energy goes if the two systems end up with a difference in their energy levels? For the one with lower internal energy at the end, what is the additional energy expenditure used for?

### Re: Reversible Expansion

Posted: Sun Feb 10, 2019 10:21 pm
If the system is isolated, then the reversible expansion wil result in a lower internal energy.