RAJASTHAN ­ PET Rajasthan PET Solved Paper-2008

  • question_answer
    Two charges are at a distance r exert a force F on each other. If the charges are doubled and distance between them is halved, then the new force acting on each charge is

    A)  \[\frac{F}{8}\]

    B)  \[\frac{F}{4}\]

    C)  \[4F\]               

    D)  \[16\,F\]

    Correct Answer: D

    Solution :

     \[F=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{q}_{1}}{{q}_{2}}}{{{r}^{2}}}\] \[F'=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{2{{q}_{1}}\times 2{{q}_{2}}}{{{\left( \frac{r}{2} \right)}^{2}}}=\frac{4}{1/4}F\] \[\Rightarrow \] \[F'=15F\Rightarrow nF=16F\]


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