NEET Sample Paper NEET Sample Test Paper-56

  • question_answer
    A gas is heated at constant pressure. The fraction of heat supplied used for external work is:

    A) \[\frac{1}{\gamma }\]                

    B) \[1-\frac{1}{\gamma }\]   

    C) \[\gamma -1\]                

    D) \[1-\frac{1}{{{\gamma }^{2}}}\]

    Correct Answer: B

    Solution :

    [b] Fraction of heat supplied used for external work is \[\frac{dW}{dQ}=\frac{dQ-dU}{dQ}=1-\frac{dU}{dQ}\] \[\frac{dW}{dQ}=1-\frac{n{{C}_{v}}\Delta T}{n{{C}_{p}}\Delta T}\] \[\frac{dW}{dQ}=1-\frac{{{C}_{v}}}{{{C}_{p}}}\] \[\frac{{{C}_{v}}}{{{C}_{p}}}=\gamma \] \[\frac{dW}{dQ}=\left[ 1-\frac{1}{\gamma } \right]\]
    Note \[dU=n{{C}_{v}}\Delta T\,\,(always)\] \[dQ=n{{C}_{P}}\Delta T\,(at\,cont.p)\] \[dQ=n{{C}_{v}}\Delta T\,(at\,cont.v)\]


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