Work Done by or on the System [ENDORSED]

[Alyssa McLeod 3E]

When using the first law of thermodynamics, how would one distinguish between work done *by* or *on* the system? If a piston compresses a gas, work is obviously done *on* the system, but what is an example of work being done *by* the system?

[Tiffany Chen 3E]

An example of work being done by a system is when the gas is expanding on the piston and it moves outwards.

[Isaiah Sandoval 1D]

To add to your question, since work is done by a system, work comes out as a negative value. When work is done by the surroundings on a system, work comes out as a positive value.

[Valeria Quintana 1G]

This question was asked during discussion today and the TA told us that to make the whole concept of "work done by or on the system" easier to understand, we should think of ourselves as the system. When something is given to us (work done by the system), we are happy (positive value). When we have to give something away (work done on the system), we are upset (negative value).

Hope this is as helpful to you as it was to me :)