KVPY Sample Paper KVPY Stream-SX Model Paper-16

  • question_answer
    A container is separated into two chambers A and B of equal volumes by a conducting wall.
    Heat cannot leave or enters the chambers A and B from outer boundary except through partition AB. Compartment A is filled with hot gas and compartment B is filled with same cold gas in equal amount. Hot gas cool down from \[65{}^\circ C\] to \[63{}^\circ C,\]choose correct,

    A) entropy change of A is more

    B) entropy change of B is more

    C) entropy change of A and B is same

    D) total entropy change of A and B is negative

    Correct Answer: B

    Solution :

    Heat lost by hot gas in A \[=-\Delta Q=-m{{C}_{V}}\Delta T\]
    Heat gained by cold gas in B \[=+\,\Delta Q=m{{C}_{V}}\Delta T\]
    Entropy change for hot gas in A is \[{{S}_{A}}=\frac{-\Delta Q}{{{T}_{A}}}=\frac{-\Delta Q}{273+65}\]
    Entropy change for cold gas in B is \[{{S}_{B}}=\frac{+\Delta Q}{273+20}\]
    Clearly, \[\left| {{S}_{B}} \right|>\left| {{S}_{A}} \right|.\]
    So, more entropy gain occurs in B than entropy loss in A. Total entropy of universe increases due to this process.


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