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BCECE Engineering BCECE Engineering Solved Paper-2002

  • question_answer
    If the heat of 110 J is added to a gaseous system, whose internal energy is 40 J, then the amount of external work done is:

    A)  80 J                       

    B)         70 J

    C)  115 J                    

    D)         140 J

    Correct Answer: B

    Solution :

    Key Idea: First law of thermodynamics is the form of law of conservation of energy. From the first law of thermodynamics which is the law of conservation of energy, if an amount of heat (Q) is given to a system, a part of it will be used in increasing the internal energy \[(\Delta U)\] of the system and the rest in doing work\[(W)\]by the system.       i.e.,     \[Q=\Delta U+W\] Given,    \[Q=110\,J,\Delta U=40\,J\]                 \[\therefore \]  \[W=Q-\Delta U\]                                 \[=110-40=70\,J\]


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