PV Diagram Isothermas and Isochloric Processes

[lc99]

Homework Statement

Homework Equations

The Attempt at a Solution

These questions are kinda tricky for me even though i might get the right answer. I just want to know if my reasonings are correct.

The answer i chose is C. For process DA, W = 0 , so delta U = Q. Q = 3/2nR(deltaT). Temp increases along DA while temp decreases along BC. So DA has a positive Q.

For process AB, W = nrt(ln(vf/vi)) . since Vf>Vi, W is positive so Q is positive.

For both processes, Q is positive which means heat flows into the gas.

 

[TSny]

For process AB, W = nrt(ln(vf/vi)) . since Vf>Vi, W is positive so Q is positive.

Why does W > 0 imply that Q > 0 for process AB?

Otherwise, everything looks OK.

 

[lc99]

Why does W > 0 imply that Q > 0 for process AB?

Otherwise, everything looks OK.

Oh. Cause deltaU = 0 for a isothermic process. Since W is positive, Q is positive.

 

[TSny]

Oh. Cause deltaU = 0 for a isothermic process. Since W is positive, Q is positive.

OK. Good work.

 

[lc99]

OK. Good work.

Thanks for the help!