JCECE Medical JCECE Medical Solved Paper-2002

  • question_answer
    N identical spherical drops are charged to the same potential V. They combine to form a bigger drop. The potential of the big drop will be:

    A) \[V{{N}^{1/3}}\]

    B) \[V{{N}^{2/3}}\]

    C)  \[V\]

    D) \[VN\]

    Correct Answer: B

    Solution :

      Key Idea: Volume of N small drops is equal to volume of single big drop. Volume of N small drops = volume of one big drop i.e.,     \[\left( \frac{4}{3}\pi {{r}^{3}} \right)N=\frac{4}{3}\pi {{R}^{3}}\] \[\Rightarrow \] \[R={{N}^{1/3}}r\] Also electric potential on big drop is \[V=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{Nq}{R}=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{Nq}{{{N}^{1/3}}r}\] \[\Rightarrow \] \[V={{N}^{2/3}}V\] \[\left( as\,V=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{q}{r} \right)\]


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