The equation W = PΔV assumes that the pressure P does not change during the
process. If P does change, then the work is equal to the area under the curve in the
P−V diagram; moving left to right gives a positive area (and positive work), while
moving right to left gives a negative area (and negative work).
- What’s the value of W for the process ab following path 1 (a to
b) and for the same process following path 2 (a to d, d to b), shown
in the P−V following diagram?