Drive an expression for excess of pressure inside a liquid drop.

Hello Student,

It is because of surface tension that pressure of a liquid increases within a bubble. Consider making free-body diagram of a bubble. If the force due to surface tension at the edge is balanced by the pressure force inside the bubble, we have
2 pi R sigma =p pi R^2
=>p=2 sigma /R
where sigma is surface tension and R is radius of the bubble and p is pressure difference.in case of soap bubble its double because that has double bubble layer.

Thanks & Regards
Arun Kumar
Askiitians Faculty
IIT Delhi