Internal Energy of Isolated Systems


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Anne 2L
Posts: 35
Joined: Fri Sep 29, 2017 7:05 am

Internal Energy of Isolated Systems

Postby Anne 2L » Sat Mar 17, 2018 4:27 pm

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?

Tim Nguyen 2J
Posts: 31
Joined: Sat Jul 22, 2017 3:00 am

Re: Internal Energy of Isolated Systems

Postby Tim Nguyen 2J » Sat Mar 17, 2018 4:32 pm

Yes, because I think that this is the first law of thermodynamics where energy is neither created nor destroyed :)

Anne 2L
Posts: 35
Joined: Fri Sep 29, 2017 7:05 am

Re: Internal Energy of Isolated Systems

Postby Anne 2L » Sat Mar 17, 2018 4:33 pm

Can you elaborate on that?

Tim Nguyen 2J
Posts: 31
Joined: Sat Jul 22, 2017 3:00 am

Re: Internal Energy of Isolated Systems

Postby Tim Nguyen 2J » Sat Mar 17, 2018 4:38 pm

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.

Anne 2L
Posts: 35
Joined: Fri Sep 29, 2017 7:05 am

Re: Internal Energy of Isolated Systems

Postby Anne 2L » Sat Mar 17, 2018 4:48 pm

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.

DamianW
Posts: 35
Joined: Fri Sep 29, 2017 7:06 am

Re: Internal Energy of Isolated Systems

Postby DamianW » Sun Mar 18, 2018 8:42 pm

constant volume means no work

Nicholas Le 4H
Posts: 74
Joined: Fri Sep 28, 2018 12:24 am

Re: Internal Energy of Isolated Systems

Postby Nicholas Le 4H » Fri Feb 01, 2019 10:40 pm

Yes, the change in internal energy of an isolated system is 0.


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