JEE Main & Advanced Sample Paper JEE Main Sample Paper-16

  • question_answer
    A solid sphere having uniform charge density p and radius R is shown in figure. A spherical R cavity of radius \[\frac{R}{2}\] is hollowed out. What is potential of O? (Assuming potential at infinity to be zero)

    A) \[\frac{11{{R}^{2}}\rho }{24{{\varepsilon }_{0}}}\]                           

    B) \[\frac{5}{12}\frac{{{R}^{2}}\rho }{{{\varepsilon }_{0}}}\]

    C) \[\frac{7\rho {{R}^{2}}}{12{{\varepsilon }_{0}}}\]                              

    D) \[\frac{3}{2}\frac{{{R}^{2}}\rho }{{{\varepsilon }_{0}}}\]

    Correct Answer: B

    Solution :

    \[{{V}_{0}}=\frac{\rho }{6{{\in }_{0}}}(3{{R}^{2}}-{{0}^{2}})\] \[-\frac{\rho }{6{{\in }_{0}}}\left( 3{{\left( \frac{R}{2} \right)}^{2}}-{{\left( \frac{R}{2} \right)}^{2}} \right)\] \[=\frac{\rho }{6{{\in }_{0}}}\left( 3{{R}^{2}}-\frac{{{R}^{2}}}{2} \right)=\frac{5{{R}^{2}}\rho }{12{{\in }_{0}}}\]


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