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NEET Sample Paper NEET Sample Test Paper-17

  • question_answer
    A gas is expanded from volume \[{{V}_{0}}\]to \[2{{V}_{0}}\] under three different processes. Process 1 is isobaric, Process 2 is isothermal, and Process 3 is adiabatic. Let \[\Delta {{U}_{1}},\] \[\Delta {{U}_{2}},\]and \[\Delta {{U}_{3}}\] be the change in internal energy of the gas in these three processes. Then

    A) \[\Delta {{U}_{1}}>\Delta {{U}_{2}}>\Delta {{U}_{3}}\]         

    B) \[\Delta {{U}_{1}}<\Delta {{U}_{2}}<\Delta {{U}_{3}}\]         

    C) \[\Delta {{U}_{2}}<\Delta {{U}_{1}}<\Delta {{U}_{3}}\]         

    D) \[\Delta {{U}_{2}}<\Delta {{U}_{3}}<\Delta {{U}_{1}}\]   

    Correct Answer: A

    Solution :

    For all processes, \[\Delta U=n{{c}_{v}}\Delta T\] For isobaric process \[\Delta {{U}_{1}}=n{{c}_{v}}\Delta T\] In isobaric expansion \[\Delta T\]is positive, therefore \[\Delta {{U}_{1}}=\]positive For isothermal process\[\Delta {{U}_{2}}=n{{c}_{v}}\Delta T=0\] For adiabatic process \[\Delta {{U}_{3}}=n{{c}_{v}}\Delta T\] In adiabatic expansion, the temperature decreases, therefore \[\Delta {{U}_{3}}\]is negative \[\therefore \]\[\Delta {{U}_{1}}>\Delta {{U}_{2}}>\Delta {{U}_{3}}.\] Hence, the correction option is [a].


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