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JEE Main & Advanced Physics Electrostatics & Capacitance Question Bank Electric Field and Potential

  • question_answer
    Three charges \[Q,(+q)\] and \[(+q)\] are placed at the vertices of an equilateral triangle of side l as shown in the figure. If the net electrostatic energy of the system is zero, then Q is equal to                                                    [MP PET 2001]

    A)            \[\left( -\frac{q}{2} \right)\]

    B)            \[(-q)\]

    C)            \[(+q)\]

    D)            Zero

    Correct Answer: A

    Solution :

                         Potential energy of the system \[U=k\frac{Qq}{l}+\frac{k{{q}^{2}}}{l}+\frac{kqQ}{l}=0\] Þ \[\frac{kq}{l}(Q+q+Q)=0\] Þ \[Q=-\frac{q}{2}\]


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