lets discuss the , concept of excess pressure

inside a bubble. if we talk about the soap bubble or a bubble made up of a liquid film.

and say we consider the wall thickness of the bubble to be very small compare to its

radius. in this situation again due to surface tension . the. liquid surface . inside as

well as outside on the, soap bubble or the liquid bubble will have a tendency to contract.

and due to which inside, say if there is a point ay and outside there is a point b, obviously

due to this contracting tendency pressure at ay will be more then pressure at b. and

at some point when the bubble will be in equilibrium we can say . the excess pressure inside is

balance by the force of the surface-tension. like what we have discussed in the case of

excess pressure inside a liquid drop. here also to analyze this excess pressure we divide

the. bubble in two hemispherical sections. and here you can see . if i just draw hemispherical

section it’ll look like this. this is the hemispherical. film of the , soap bubble or

the liquid bubble. and in this situation we can say . the right part will exert a force

. on it in outward direction due to excess pressure. and this outward force can be simply

written as excess pressure multiplied by the surface area which is pie r square that is

the . area of this . hemispherical , base. which is pie r square. and on the two sircumferences

in. inward direction surface tension will exert a force that is t into two pie r. and

on both the surfaces it’ll be t into two pie r and we can take the radius of. the two

surfaces to be r as. the film thickness or wall thickness of this bubble can be considered

to be very small. so in this situation we can say . for, iquilibrium of. hemispherical

. section. of the bubble. we can use. in this situation it is excess pressure multiplied

by pie r square that is outward force must be balance by twice of . t into two pie r

. in this situation pie and r gets cancelled out ,and. excess pressure can be written as

. four t by r . this exactly double that of the excess pressure inside a liquid drop because

here there are two , liquid surfaces where as in case of drop only outer surface exist

. that’s why the excess pressure, in a soap bubble or a liquid bubble, is double then

that of. the liquid drop of same radius , made up of same, solution. so just be careful about

this expression of excess pressure inside a bubble.

not natural

Is the excess pressure p. Pi R^2 or p. 2 pi R^2?