KVPY Sample Paper KVPY Stream-SX Model Paper-5

  • question_answer
    Which one of the following equations does not correctly represent the first law of thermodynamics for the given processes involving an ideal gas? (Assume non-expansion work is zero)

    A) Adiabatic process : \[\Delta U=-\,W\]

    B) Cyclic process : \[q=-\,W\]

    C) Isothermal process : \[q=-W\]

    D) Isochoric process : \[\Delta U=q\]

    Correct Answer: A

    Solution :

    1st law of thermodynamics \[\Delta E=q+w\]
    1. Adiabatic process
    \[q=0,(\Delta E=w)or\,(\Delta U=w)\]
    2. Cyclic process
    \[\Delta E=0,(q=-w)\]
    3. Isothermal process
    \[\Delta E=n{{C}_{V}}\Delta T.(\Delta T=0)\]
    \[\Delta E=0,(q=-w)\]
    4. Isochoric process \[\Delta V=0\]
    \[W=P\Delta V=0\]
    \[\Delta E=q.\]

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