NEET Physics Thermodynamical Processes NEET PYQ-Thermodynamical Processes

  • question_answer
    An ideal gas goes from state A to state B via three different processes as indicated in the p-V diagram. If  \[{{Q}_{1}},\,\,{{Q}_{2}},\,\,{{Q}_{3}}\] indicate the   heat absorbed by the gas along the three processes and \[\Delta {{U}_{1}},\Delta {{U}_{2}},\Delta {{U}_{3}}\] indicate the change in internal energy along the three processes respectively, then                                                                                                            [AIPMT (M) 2012]

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

    B)  \[{{Q}_{3}}>{{Q}_{2}}>{{Q}_{1}}\] and \[\Delta {{U}_{1}}=\Delta {{U}_{2}}=\Delta {{U}_{3}}\]

    C)  \[{{Q}_{1}}={{Q}_{2}}={{Q}_{3}}\] and \[\Delta {{U}_{1}}>\Delta {{U}_{2}}>\Delta {{U}_{3}}\]

    D)  \[{{Q}_{3}}>{{Q}_{2}}>{{Q}_{1}}\] and \[\Delta {{U}_{1}}>\Delta {{U}_{2}}>\Delta {{U}_{3}}\]

    Correct Answer: A

    Solution :

    For all process 1, 2 and 3
                \[\Delta U={{U}_{B}}-{{U}_{A}}\] is same
                \[\therefore \]      \[\Delta {{U}_{1}}=\Delta {{U}_{2}}=\Delta {{U}_{3}}\]
                Now,     \[\Delta Q=\Delta U+\Delta W\]
    Now,     \[\Delta W=\]work done by the gas
    \[\therefore \]      \[\Delta {{Q}_{1}}=\Delta {{Q}_{2}}>\Delta {{Q}_{3}}\]


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