An isolated and charged spherical soap bubble has a radius r and the pressure inside is atmospheric. IfT is the surface tension of soap solution, then charge on drop is` Xpi sqrt(2r T epsi _(0))` then find the value of X.

Options

A. 8
B. 9
C. 7
D. 2

Answer

A

Explanation

Inside pressure must be `(4T)/(r )` greater than outside pressure in bubble.
This excess pressure is provided by charge on bubble.
`(4T)/(r ) = (sigma ^(2))/( 2 epsi _(0)) , ( 4T)/(r) = ( Q ^(2))/( 16 pi ^(2) r ^(4) xx 2 epsi _(0)) [ sigma = (Q)/( 4 pi r ^(2)) ]`
` Q = 8 pi r sqrt ( 2 r T epsi 0)`