NEET Sample Paper NEET Sample Test Paper-37

  • question_answer
    If identical charges (-q) are placed at each corner of a cube of side b, then electric potential energy of charge (+q) which is placed at centre of the cube will be

    A) \[\frac{8\sqrt{2}{{q}^{2}}}{4\pi {{\varepsilon }_{0}}b}\]

    B) \[\frac{-8\sqrt{2}{{q}^{2}}}{\pi {{\varepsilon }_{0}}b}\]

    C) \[\frac{-4\sqrt{2}{{q}^{2}}}{\pi {{\varepsilon }_{0}}b}\]

    D) \[\frac{-4{{q}^{2}}}{\sqrt{3}\pi {{\varepsilon }_{0}}b}\]  

    Correct Answer: D

    Solution :

     Length of the diagonal of a cube having each side b is \[\sqrt{3}b.\]So distance of centre of cube from each vertex is \[\frac{\sqrt{3}b}{2}.\] Hence potential energy of the given system of charge is \[U=8\times \left\{ \frac{1}{4\pi {{\varepsilon }_{0}}}.\frac{(-q)(q)}{\sqrt{3}b/2} \right\}=\frac{-4{{q}^{2}}}{\sqrt{2}\pi {{\varepsilon }_{0}}b}\]


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