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Chhattisgarh PMT Chhattisgarh 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 \[E=T\times 2A\] 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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