Change in Volume

[Mary Koutures 2I]

Hey everyone! Before the final, I wanted to ask if the change in volume in the equation w=-PdeltaV is always positive? Or is it only positive when the volume increases?

[ruby_sievers_3H]

If change in volume is negative, work is being done by the surroundings and w will be positive. So yes, change in volume can be negative.

[505997354]

V is positive only when it increases. :) If it decreases it would be negative.

[Varun Nair 3L]

Hi,

Great question! Since deltaV is one of the components in the equation, the change in volume can be negative given that the final volume is smaller than the initial volume (the system is compressed instead of expanded). Since compressing requires energy, work would be positive in this case, which makes sense as -Pext*a deltaV < 0 would be a positive number.

Hope this helps!