Expansion work/ Compression

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aphung1E
Posts: 101
Joined: Sat Aug 24, 2019 12:15 am

Expansion work/ Compression

Postby aphung1E » Mon Feb 03, 2020 8:19 pm

for expansion do you need to include a negative sign when calculating values
what about compression?

Hiba Alnajjar_2C
Posts: 108
Joined: Fri Aug 09, 2019 12:17 am

Re: Expansion work/ Compression

Postby Hiba Alnajjar_2C » Mon Feb 03, 2020 8:21 pm

When expansion takes place, work is being done and is therefore negative. When compression takes place, work is positive.

kristi le 2F
Posts: 102
Joined: Thu Jul 11, 2019 12:15 am

Re: Expansion work/ Compression

Postby kristi le 2F » Thu Feb 06, 2020 1:12 pm

Remember that the sign for work is always in regard to the system. In expansion, the system is doing the work and is therefore losing energy so work is negative. In compression, work is being done on the system, so work will be a positive value.

Uisa_Manumaleuna_3E
Posts: 60
Joined: Wed Sep 21, 2016 2:56 pm

Re: Expansion work/ Compression

Postby Uisa_Manumaleuna_3E » Fri Feb 07, 2020 1:27 pm

Expansion and compression both denote work, but they exert that work in opposite directions. It helps me keep in mind the visual of a balloon expanding and deflating. Both require a change of energy or movement, but one obviously has a positive growth and the other a negative.

You just have to remember that when an object does do work (balloon expanding/expansion) that object or system LOSES that energy so its a negative.
When an object undergoes compression (balloon shrinking/compression) that object has work acted on it by something else so it GAINS energy and is positive.

Abby Soriano 1J
Posts: 103
Joined: Sat Aug 24, 2019 12:16 am

Re: Expansion work/ Compression

Postby Abby Soriano 1J » Fri Feb 07, 2020 1:34 pm

Things like work and heat should always be approached from the point of view of the system. Just as when heat is being applied to a system and delta H is a positive value, when work is being done on/to a system, the value of work is positive. When the system is doing work to its surroundings, work is negative.

stephaniekim2K
Posts: 79
Joined: Fri Aug 09, 2019 12:16 am

Re: Expansion work/ Compression

Postby stephaniekim2K » Sun Feb 09, 2020 7:48 pm

During expansion, work is being done so you need a negative sign while compression you need a positive sign.

Kennedi2J
Posts: 101
Joined: Wed Sep 18, 2019 12:20 am

Re: Expansion work/ Compression

Postby Kennedi2J » Sun Feb 09, 2020 8:10 pm

w = (+) when work is done on the system (compression)
w = (-) when work is done by the system (expansion)

Veronica Lu 2H
Posts: 89
Joined: Wed Sep 18, 2019 12:18 am
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Re: Expansion work/ Compression

Postby Veronica Lu 2H » Sun Feb 09, 2020 9:58 pm

negative work means work is being done (expansion) whereas positive work signifies work is done on the system (compression)


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