- #1
Grand
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Homework Statement
A soap bubble of radius [tex]R_1[/tex] and surface tension [tex]\gamma[/tex] is expanded at constant temperature by forcing in air by driving in fully a piston containing volume [tex]v[/tex]. We have to show that the work needed to increase the bubble's radius to [tex]R_2[/tex] is:
[tex]\Delta W=P_2V_2ln\frac{P_2}{P_1} + ...[/tex]
I know hoow to work out the dots (due to surface tension and work against the atmosphere. But for the first term I need to work out the integral:
[tex]\int_{V_1+v}^{V_2} PdV[/tex]
which I don't really know how to do. If I apply the ideal gas law, I pick a minus sign on the way.