# PV diagram full circle cycle help

1. Feb 28, 2010

### blackdog666

1. The problem statement, all variables and given/known data

I'm given a PV diagram, it goes from A, B, C, D, in a full circle, counter-clock wise. A is at the top, and is at 30 Pa and 25 m^3 for volume. B is at 20 Pa and 15 m^3. C is at 10 Pa and 25 m^3, and D is at 20 Pa and 35 m^3 (It goes in a full circle with A and C having the same volume, and B and D having the same pressure) Sorry I can't post a real picture of it. The question now asks:

Calculate:

A) The total internal energy in a full cycle from A-->B-->C-->D-->A

B) The total work done on or by the system in a full cycle from A-->B-->C-->D-->A.

C) The total heat flow in a full cycle from A-->B-->C-->D-->A

D) The work done on or by the system from A-->B-->C

2. Relevant equations

PV=nRT
(delta)U = Q - W

3. The attempt at a solution

I've thought about A, and see that in a full cycle the total change in internal energy would be 0, however I don't think that it's asking for the total change, just the total. Also for B, C, and D I'm having trouble trying to find the right equation, as I can't determine if this cycle would be isobaric, isochoric, isothermal, or adiabatic. Please help.

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