Manipal Medical Manipal Medical Solved Paper-2012

  • question_answer
    The potential of a large liquid drop when eight liquid drops are combined is 20 V. Then, the potential of each single drop was

    A)  10 V            

    B)  7.5V

    C)  5V            

    D)  2.5V

    Correct Answer: A

    Solution :

     Volume of 8 drops = Volume of big drop \[\therefore \] \[\left( \frac{4}{3}\pi {{r}^{3}} \right)\times 8=\frac{4}{3}\pi {{R}^{3}}\] \[\Rightarrow \] \[2r=R\]              ...(i) According to charge conservation \[8q=Q\]               ...(ii) We have \[V\propto \frac{1}{r}\] Or \[\frac{{{V}_{1}}}{{{V}_{2}}}=\frac{{{r}_{2}}}{n}\] \[\Rightarrow \] \[\frac{20}{{{V}_{2}}}=\frac{2r}{r}\] \[\Rightarrow \] \[{{V}_{2}}=10\,V\]


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