-PDeltaV

[Namita Shyam 3G]

I understand that we use w=-PDeltaV when pressure is constant, but then why don't we use this equation on Sapling (week 3 and 4 hw) number 14 for path A? I know they said that Path A is an isothermal, reversible expansion, but why would it be like that if the pressure is constant (2.62 atm)?

[Kiran Marla]

I think this is because isothermal expansions signify a non constant pressure!

[Eliot Kagan 2G]

Remember that the P in w=-PDeltaV signifies external pressure. When something undergoes a reversible expansion, they change the external pressure and internal pressure with infinitely small intervals. This is why reversible expansions take more work.