Properties of matterMedium
Question
The radius of a soap bubble is r. The surface tension of soap solution is T. Keeping temperature constant, the radius of the soap bubble is doubled, the energy necessary for this will be : -
Options
A.24 πr2 T
B.8 πr2 T
C.12 πr2 T
D.16 πr2 T
Solution
Initial surface energy
= 2 × T × 4πr2 = 8πr2T
Final surface energy
= 2 × T × 4π(2r)2 = 32πr2T
So energy needed
= 32πr2T = 8πr2T = 24πr2T
= 2 × T × 4πr2 = 8πr2T
Final surface energy
= 2 × T × 4π(2r)2 = 32πr2T
So energy needed
= 32πr2T = 8πr2T = 24πr2T
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