w and q
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Elizabeth Gallmeister 1A
- Posts: 41
- Joined: Fri Sep 28, 2018 12:21 am
w and q
I know that deltaU = w + q, but is there a definitive way to know when each of these values is positive or negative? Like if work is done on the system vs done by the system, etc etc. Thanks!
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deniise_garciia
- Posts: 30
- Joined: Wed Nov 16, 2016 3:04 am
Re: w and q
Hey Elizabeth,
So, ∆U= q + w, when they are (+) or (-),
Energy entering a system carries a (+) sign
If heat is absorbed by the system then q is > 0 (+)
If work is DONE ON A SYSTEM w>0 (+)
Energy leaving a system carries a (-) sign giving off energy
If heat is GIVEN OFF BY A SYSTEM q<0 (-)
If work is DONE BY A SYSTEM w<0 (-)
So, ∆U= q + w, when they are (+) or (-),
Energy entering a system carries a (+) sign
If heat is absorbed by the system then q is > 0 (+)
If work is DONE ON A SYSTEM w>0 (+)
Energy leaving a system carries a (-) sign giving off energy
If heat is GIVEN OFF BY A SYSTEM q<0 (-)
If work is DONE BY A SYSTEM w<0 (-)
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