JEE Main & Advanced Physics Thermodynamical Processes JEE PYQ-Thermodynamical Processes

  • question_answer
    One mole of an ideal gas passes through a process where pressure and volume obey the relation \[P={{P}_{0}}\left[ 1-\frac{1}{2}{{\left( \frac{{{V}_{0}}}{V} \right)}^{2}} \right].\] Here \[{{P}_{0}}\]and \[{{V}_{0}}\] are constants. Calculate the change in the temperature of the gas if its volume changes from \[{{V}_{0}}\] to \[2{{V}_{0}}\]. [JEE Main 10-4-2019 Afternoon]

    A) \[\frac{1}{2}\frac{{{P}_{0}}{{V}_{0}}}{R}\]   

    B)      \[\frac{3}{4}\frac{{{P}_{0}}{{V}_{0}}}{R}\]

    C) \[\frac{5}{4}\frac{{{P}_{0}}{{V}_{0}}}{R}\]   

    D)      \[\frac{1}{4}\frac{{{P}_{0}}{{V}_{0}}}{R}\]

    Correct Answer: C

    Solution :

    [c] \[P={{P}_{0}}\left[ 1-\frac{1}{2}{{\left( \frac{{{V}_{0}}}{V} \right)}^{2}} \right]\]
    Pressure at \[{{V}_{0}}={{P}_{0}}\left( 1-\frac{1}{2} \right)=\frac{{{P}_{0}}}{2}\]
    Pressure at\[2{{V}_{0}}={{P}_{0}}\left( 1-\frac{1}{2}\times \frac{1}{4} \right)=\frac{7}{8}{{P}_{0}}\]
    Temperature at \[{{V}_{0}}=1-\frac{\frac{{{P}_{0}}}{2}{{V}_{0}}}{nR}=\frac{{{P}_{0}}{{V}_{0}}}{2nR}\]
    Temperature at \[2{{V}_{0}}=\frac{\left( \frac{7}{8}{{P}_{0}} \right)(2{{V}_{0}})}{nR}=\frac{\frac{7}{4}{{P}_{0}}{{V}_{0}}}{nR}\]
    Change in temperature\[=\left( \frac{7}{4}-\frac{1}{2} \right)\frac{{{P}_{0}}{{V}_{0}}}{nR}\]
    \[=\frac{5}{4}\frac{{{P}_{0}}{{V}_{0}}}{nR}=\frac{5{{P}_{0}}{{V}_{0}}}{4R}\]


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