Work sign changes


Moderators: Chem_Mod, Chem_Admin

Posts: 69
Joined: Fri Sep 28, 2018 12:25 am

Work sign changes

Postby rkang00 » Sun Feb 03, 2019 10:16 pm

Typically if a system is compressed, is the sign for work + and - for expansion?
If so, what's the reason?

Hannah Yates 1K
Posts: 59
Joined: Fri Sep 28, 2018 12:27 am

Re: Work sign changes

Postby Hannah Yates 1K » Sun Feb 03, 2019 10:23 pm

I think work is negative when the system is doing work, and positive when the system is getting work done to it. So when a system expands, work is negative, and when a system is compressed, work is positive.
I might be wrong though

Cole Doolittle 2K
Posts: 30
Joined: Fri Sep 28, 2018 12:20 am

Re: Work sign changes

Postby Cole Doolittle 2K » Sun Feb 03, 2019 10:27 pm

I believe this is because the formula is w = - P (delta V). If it is expansion, delta V will be positive and thus work negative. In compression delta V is negative and thus work is positive.

Posts: 65
Joined: Fri Sep 28, 2018 12:16 am

Re: Work sign changes

Postby deepto_mizan1H » Mon Feb 04, 2019 10:00 am

When the system is expanding, the volume will be a positive value, ultimately making the work value negative.

When it's compressed, the volume will be a negative value, which makes the work in total a positive value.

So, when the system does work, it is negative. When work is done on the system, it'll be a positive value. Thinking of this in terms of the delta V and its sign will help to conceptualize why the work changes sign based on what is being done.

Return to “Calculating Work of Expansion”

Who is online

Users browsing this forum: No registered users and 2 guests