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JEE Main & Advanced Physics Thermodynamical Processes Question Bank Graphical Questions

  • question_answer
    A thermodynamic process is shown in the figure. The pressures and volumes corresponding to some points in the figure are : \[{{P}_{A}}=3\times {{10}^{4}}Pa,\ {{P}_{B}}=8\times {{10}^{4}}Pa\]   and   \[{{V}_{A}}=2\times {{10}^{-3}}{{m}^{3}},\ {{V}_{D}}=5\times {{10}^{-3}}{{m}^{3}}\]            In process AB, 600 J of heat is added to the system and in process BC, 200 J of heat is added to the system. The change in internal energy of the system in process AC would be                                                                [CBSE PMT 1992]

    A)            560 J

    B)            800 J

    C)            600 J

    D)            640 J

    Correct Answer: A

    Solution :

                       By adjoining graph \[{{W}_{AB}}=0\] and     \[{{W}_{BC}}=8\times {{10}^{4}}[5-2]\times {{10}^{-3}}=240\,J\] \ \[{{W}_{AC}}={{W}_{AB}}+{{W}_{BC}}=0+240=240\,J\] Now, \[\Delta {{Q}_{AC}}=\Delta {{Q}_{AB}}+\Delta {{Q}_{BC}}=600+200=800\,J\] From FLOT \[\Delta {{Q}_{AC}}=\Delta {{U}_{AC}}+\Delta {{W}_{AC}}\] Þ \[800=\Delta {{U}_{AC}}+240\] Þ \[\Delta {{U}_{AC}}=560\,J.\]


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