MGIMS WARDHA MGIMS WARDHA Solved Paper-2015

  • question_answer
    During adiabatic expansion, the volume of air increases by 4%. The percentage decrease in the pressure will be

    A)  3.2%

    B)                         5.6%   

    C)  1.5%                    

    D)  4.8%

    Correct Answer: B

    Solution :

                    For an adiabatic change \[p{{V}^{\gamma }}=\]constant Taking logarithm on both sides \[log\text{ }p+\gamma \text{ }log\text{ }V=log\] ( constant) \[\Rightarrow \]               \[\frac{dp}{p}+\gamma \frac{dV}{V}=0\] \[\Rightarrow \]               \[\frac{dp}{p}=-\gamma \frac{dV}{V}=0\] For air,     \[\gamma =\frac{{{C}_{p}}}{{{C}_{V}}}=14\] So,         \[\frac{dp}{p}=-14\times -\frac{4}{100}\]                 \[\frac{dp}{p}\times 100=-5.6%\] So, percentage decrease in the pressure will be 5.6%.


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