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Internal Energy of Isolated Systems

Posted: Sat Mar 17, 2018 4:27 pm
by Anne 2L
I read this in the course reader:

The energy of an isolated system must remain constant because no matter or heat can be transferred and the system cannot be physically changed (V=0).
q=0 and w=0 then U=q+w=0

I just wanted to confirm that the internal energy of all isolated systems is 0? So for example, the internal energy of a system in a bomb calorimeter would always be 0?

Re: Internal Energy of Isolated Systems

Posted: Sat Mar 17, 2018 4:32 pm
by Tim Nguyen 2J
Yes, because I think that this is the first law of thermodynamics where energy is neither created nor destroyed :)

Re: Internal Energy of Isolated Systems

Posted: Sat Mar 17, 2018 4:33 pm
by Anne 2L
Can you elaborate on that?

Re: Internal Energy of Isolated Systems

Posted: Sat Mar 17, 2018 4:38 pm
by Tim Nguyen 2J
Yeah of course! As Dr. Lavelle discussed in class, the internal energy of an isolated system is constant. Since the universe is defined as an isolated system, the summation of all the work and heat transferred in the universe is constant. Therefore the change in internal energy (delta U) of the universe is zero.

Re: Internal Energy of Isolated Systems

Posted: Sat Mar 17, 2018 4:48 pm
by Anne 2L
Thank you so much for all the help!

I was just wondering how having constant internal energy equates to energy being neither created nor destroyed.

Re: Internal Energy of Isolated Systems

Posted: Sun Mar 18, 2018 8:42 pm
by DamianW
constant volume means no work

Re: Internal Energy of Isolated Systems

Posted: Fri Feb 01, 2019 10:40 pm
by Nicholas Le 4H
Yes, the change in internal energy of an isolated system is 0.