Don't have point B (cycle process)

[Doc Al]

$\int p dv$ is the work done by the gas. When the volume increases, it's positive.

$-\int p dv$ is the work done on the gas. When the volume increases, it's negative.

Either one is fine, depending upon the sign convention used in your course. In your first post you wrote:

$$\Delta U= Q + W$$

That tells me you want the second version, the work done on the gas.

 

[~christina~]

$\int p dv$ is the work done by the gas. When the volume increases, it's positive.

$-\int p dv$ is the work done on the gas. When the volume increases, it's negative.

Either one is fine, depending upon the sign convention used in your course. In your first post you wrote:

$$\Delta U= Q + W$$

That tells me you want the second version, the work done on the gas.

I've gotten myself confused...I looked up this equation online and my teacher gave the class another equation and my book has the same one that I first posted.

so the only difference would be that it would be +/- in the end so if I made the calculations with in on the gas then the result would be (-).

but if the volume decreases then the work would be possitive

sooo, I've decided to use the one done on the gas.

Thanks very much for your explanation.