Question

The radius of a soap bubble is blown up to double its value under isothermal conditions. If 'r' be the initial radius of the bubble, and T be the surface tension, then energy spent in doubling the radius is ______

Options

• 4πr²T

• 8πr²T

• 16πr²T

• 24πr²T

Answer 1

The radius of a soap bubble is blown up to double its value under isothermal conditions. If 'r' be the initial radius of the bubble, and T be the surface tension, then energy spent in doubling the radius is 24πr²T.

Explanation:

Increase in surface area = `4pi(2r)^2 - 4pir^2`

= `12pir^2` Soap bubble of two surfaces.

So increase in surface energy is `T xx (12pir^2) xx 2 = 24 pir^2 T`.