CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2000

  • question_answer
    \[n\]identical droplets charged to the same potential\[V\]coalesce to form a single bigger drop. The potential of the new drop will be:

    A) \[nV\]                                  

    B) \[\frac{V}{n}\]

    C)  \[{{n}^{2/3}}V\]                              

    D) \[n{{V}^{2}}\]

    Correct Answer: C

    Solution :

    Since \[n\] drops of radius r coalesced, hence \[\frac{4\pi {{R}^{3}}}{3}=n\frac{4}{3}\pi {{r}^{3}}\] \[R=r{{n}^{1/3}}\] The potential is given by the formula                                 \[V=\frac{q}{4\pi {{\varepsilon }_{0}}r}\] Now, potential of bigger drop is                 \[\frac{nq}{4\pi {{\varepsilon }_{0}}R}=n\frac{q}{4\pi {{\varepsilon }_{0}}r{{n}^{1/3}}}\]                 \[={{n}^{1-\frac{1}{3}}}.V={{n}^{2/3}}V.\]


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