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RAJASTHAN PMT Rajasthan - PMT Solved Paper-2008

  • question_answer
    A frame made of metallic wire enclosing a surface area A is covered with a soap film. If the area of the frame of metallic wire is reduced by 50%, the energy of the soap film will be changed by

    A)  100%                                   

    B)  75%

    C)  50%                      

    D)         25%

    Correct Answer: C

    Solution :

    Surface energy = surface tension \[\times \] surface area                 \[E=T\times 2\,\,A\] New surface energy,                 \[{{E}_{1}}=T\times 2\left( \frac{A}{2} \right)=T\times A\] \[%\]decrease in surface energy                 \[=\frac{E-{{E}_{1}}}{E}\times 100\]                 \[=\frac{2TA-TA}{2TA}\times 100\]                                 \[=50%\]


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