Work done on or by the system

$\Delta U=q+w$

vanessas0123
Posts: 100
Joined: Wed Sep 11, 2019 12:17 am

Work done on or by the system

How do you know if the work is done on or by the system? Which one would be negative and which one would be positive?

Jordan Young 2J
Posts: 102
Joined: Thu Jul 25, 2019 12:17 am
Been upvoted: 1 time

Re: Work done on or by the system

If work is done by the system then your work value for the system would be negative because the system is losing energy due to work. If the work is done on the system, you work value for the system would be positive because the system is gaining energy.

Anthony Hatashita 4H
Posts: 103
Joined: Wed Sep 18, 2019 12:21 am

Re: Work done on or by the system

If the system is doing work, it is losing energy, so it is negative. Think of it with yourself as the system, if you open a door you are transferring energy to the door, losing energy yourself (-).

205291012
Posts: 50
Joined: Mon Nov 11, 2019 12:17 am

Re: Work done on or by the system

If the system is doing work then it is losing energy so the value will be negative. If work is done on the system, it is gaining energy so it will be positive. similarly, if a system loses heat, it is negative. if it gains heat, it is positive.

Jessica Katzman 4F
Posts: 35
Joined: Mon Jun 17, 2019 7:24 am

Re: Work done on or by the system

If work is done BY the system, w is negative. If work is done on the system, w is positive.