Why is W = -PV?
GeneralClass 12AllAnswered 27 Mar 2026
Answer
The complete form is W = -PΔV. The negative sign is a sign convention:
- When gas expands (ΔV positive): System does work on surroundings (W positive)
- When gas compresses (ΔV negative): Surroundings do work on system (W negative)
This convention ensures thermodynamic consistency with the first law: ΔU = Q - W.
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