JEE Main & Advanced Physics Electrostatics & Capacitance NEET PYQ - Electrostatics and Capacitance

  • question_answer
    Identical charges \[(-q)\] are placed at each corners of a cube of side b, then the electrostatic potential energy of charge \[(+q)\] placed at the centre of the cube will be:

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

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

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

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

    Correct Answer: C

    Solution :

    [c] Electrostatic potential energy of charge +q placed at the centre of cube is
                            \[U=8\times \frac{1}{4\pi {{\varepsilon }_{0}}}\times \frac{q\,(-q)}{\text{half-diagonal}\,\text{distance}}\]
                            \[=8\times \frac{1}{4\pi {{\varepsilon }_{0}}}\frac{-{{q}^{2}}}{b\frac{\sqrt{3}}{2}}\]
                            \[=\frac{-4{{q}^{2}}}{\sqrt{3}\pi {{\varepsilon }_{0}}b}\]


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