A) \[6\times {{10}^{-2}}J\]
B) \[6\times {{10}^{-4}}J\]
C) \[3\times {{10}^{-2}}J\]
D) \[3\times {{10}^{-4}}J\]
Correct Answer: B
Solution :
Key Idea : Surface tension T can be defined as the work done informing the soap film of unit surface area. Surface tension of a soap film is written as \[T=\frac{work\text{ }done}{area}\] or Work done = T \[\times \]area Here, area \[=2\times 10\times 10\,c{{m}^{2}}=2\times {{10}^{-2}}{{m}^{2}}\], \[T=3\times {{10}^{-2}}N/m\] Hence, work done \[=3\times {{10}^{-2}}\times 2\times {{10}^{-2}}\] \[=6\times {{10}^{-4}}J\]
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