Delta U when temperature is constant


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Christopher Kan 2J
Posts: 15
Joined: Fri Sep 25, 2015 3:00 am

Delta U when temperature is constant

Postby Christopher Kan 2J » Thu Feb 11, 2016 9:16 pm

If given that the temperature is constant, is delta U = work because q=mCdeltaT and if there is no change in T, T=0 and so q=0?

Ronald Yang 2F
Posts: 86
Joined: Fri Sep 25, 2015 3:00 am

Re: Delta U when temperature is constant

Postby Ronald Yang 2F » Thu Feb 11, 2016 9:51 pm

When change in T is zero, that doesn't mean q=o. When temperature is constant, delta U is zero, shown by the relationship delta U = 3/2*n*R*delta T. An application to this is for a reversible, isothermal expansion. Since delta U=0, q+w=0, so q=-w. In this case, q is not equal to zero. In fact, heat is put into the system to keep the temperature constant when a gas expands reversibly.


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