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Punjab Medical Punjab - MET Solved Paper-2007

  • question_answer
    A gas is compressed at a constant pressure of \[50N/{{m}^{2}}\] from a volume of \[10{{m}^{3}}\] to a volume of\[4{{m}^{3}}\]. Energy of \[100J\] is thus added to die gas by heating. Its internal energy is

    A)  decreased by\[200J\]

    B)  increased by\[100J\]

    C)  increased by\[300J\]

    D)  increased by\[400J\]

    Correct Answer: D

    Solution :

    Change in volume                 \[\Delta V={{V}_{2}}-{{V}_{1}}\]                 \[=4-10=-6{{m}^{3}}\] As volume decreases, work is done on the gas and so it is negative                 \[W=P\Delta V\]                 \[=50\times (-6)=-300J\] Heat supplied\[Q=100J\] According to first law of thermodynamics change in internal energy is                 \[\Delta U=Q-W\]                         \[=100-(-300)\]                         \[=400J\] It means internal energy increase by\[=400J\].


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