12th Class Physics Electrostatics & Capacitance Question Bank Case Based (MCQs) - Electric Potential and Capacitance

  • question_answer
      Four equal charges q each are placed at four comers of a square of side a each. Work done in carrying a charge -q from its centre to infinity is

    A) zero

    B) \[\frac{\sqrt{2}q}{\pi {{\varepsilon }_{0}}a}\]

    C) \[\frac{\sqrt{2}q}{\pi {{\varepsilon }_{0}}a}\]

    D) \[\frac{{{q}^{2}}}{\pi {{\varepsilon }_{0}}a}\]

    Correct Answer: B

    Solution :

    Potential at the centre of the square due to four equal charges q at four comers \[V=\frac{4q}{4\pi {{\varepsilon }_{0}}\left( a\sqrt{2} \right)/2}=\frac{\sqrt{2}q}{\pi {{\varepsilon }_{0}}a}\] \[{{W}_{0\to \infty }}=-{{W}_{\infty \to 0}}=-\left( -q \right)V=\frac{\sqrt{2}{{q}^{2}}}{\pi {{\varepsilon }_{0}}a}\]


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