• id: JTHERM-01-N05
• title: Work as Area Under P-V Curve
• tags: work, PV-diagram, path-dependent

Work done by gas: $W = \int P \, dV$. Graphically, work is the area under the P-V curve. For expansion ($V_2 > V_1$), W > 0. For compression, W < 0. Work is path-dependent — the same initial and final states can have different work values depending on the process. In a cyclic process (closed loop on P-V), net work = area enclosed. Clockwise loop = positive work (engine), counterclockwise = negative work (work done ON gas, refrigerator).