# Difference between revisions of "Work"

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The mechanical work, W, performed upon a gas is given by

$W = - \int_\alpha^\beta p ~dV$

where $\alpha$ and $\beta$ are points in state space, p is the pressure and V is the volume. The mechanical work done by the gas has the opposite sign (a common source of mistakes).

For reversible changes,

$\left.dW\right.=-p~dV$

and for irreversible changes

$\left.dW\right. > -p~dV$