Radius of a soap bubble is increased from R to 2R work done in this process in terms of surface tension is
Correct Answer :
24π R²S
Solution :
The correct option is 24π R²S.
Underlying Concept:
A soap bubble has two free surfaces in contact with air (one inner surface and one outer surface). Therefore, when calculating the total surface area of a soap bubble, we must multiply the area of a single sphere by 2.
The work done () in expanding a soap bubble is equal to the product of its surface tension () and the increase in its total surface area ():
Step-by-Step Derivation:
1. Initial Surface Area ():
For an initial radius , the total initial surface area is:
2. Final Surface Area ():
When the radius is increased to , the total final surface area becomes:
3. Change in Surface Area ():
The increase in surface area is:
Substituting the values:
4. Work Done ():
Using the relation for work done:
Substituting the change in area:
Therefore, the work done in this process is 24π R²S.
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