Positive and Negative Boundary Work

Think about our

sign convention

for work.
P > 0, always.
When dV > 0, the gas expands and W > 0.
When dV < 0, the gas is compressed and W < 0.
Boundary work is the integral of P dV from state 1 to state 2.
Here we see our process from State 1 (high pressure, small volume) to State 2 (low pressure, large volume).
PV diagram that shows that as the pressure on the back of the piston is reduced, the gas expands and the volume increases from state 1 to state 2. between states 1 and 2.
Here is a P-V Diagram showing the initial and final states of our system.
x
The x-coordinate is measured from left to right, with the origin at the initial position of the piston in the horizontal cylinder.
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Ch 4, Lesson A, Page 10 - Positive and Negative Boundary Work