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JEE Main & Advanced Sample Paper JEE Main - Mock Test - 9

  • question_answer
    A large number of water drops each of radius r combine to have a drop of radius R. If the surface tension is T and the mechanical equivalent of heat is J, then the rise in temperature will be

    A) \[\frac{2T}{rJ}\]

    B) \[\frac{3T}{RJ}\]

    C) \[\frac{3T}{J}\left( \frac{1}{r}-\frac{1}{R} \right)\]          

    D) \[\frac{2T}{J}\left( \frac{1}{r}-\frac{1}{R} \right)\]

    Correct Answer: C

    Solution :

    Rise m temperature, \[\Delta \theta =\frac{3T}{JSd}\,\left( \frac{1}{r}-\frac{1}{R} \right)\] \[\therefore \,\,\Delta \theta =\frac{3T}{J}\,\left( \frac{1}{r}-\frac{1}{R} \right)\]    (For water \[S=1\] and \[d=1\])


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