EAMCET Medical EAMCET Medical Solved Paper-2008

  • question_answer
    A charge Q is placed at each comer of a cube of side a. The potential at the centre of the cube is

    A)  \[-\frac{Q}{2}\]                               

    B)  \[+\frac{Q}{2}\]

    C)   \[-\frac{Q}{4}\]                                              

    D)  \[+\frac{Q}{4}\]

    Correct Answer: C

    Solution :

                     Let \[{{V}_{1}}\]be the potential at the centre of the cube due to one charge. \[{{V}_{1}}=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{Q}{x}\]                 and        \[x=\frac{a\sqrt{3}}{2}\] Potential due to all eight comers of the cube \[\Rightarrow \]                               \[V=8{{V}_{1}}\]                                 \[=8\left[ \frac{1}{4\pi {{\varepsilon }_{0}}}\frac{Q}{\sqrt{\frac{3}{2}}\times a} \right]\] \[=\frac{16Q}{4\pi {{\varepsilon }_{0}}\sqrt{3}\times a}\] \[=\frac{4Q}{a\sqrt{3}\pi {{\varepsilon }_{0}}}\]


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