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JEE Main & Advanced Sample Paper JEE Main Sample Paper-11

  • question_answer
    Three charges Q, + q and +q are placed at the vertices of a right-angled isosceles triangle as shown. The net electrostatic energy of the configuration is zero if Q is equal to

    A)  \[\frac{-q}{1+\sqrt{2}}\]                             

    B)  \[\frac{-2q}{2+\sqrt{2}}\]

    C)  \[-2q\]                                

    D)  \[+q\]

    Correct Answer: B

    Solution :

     Here we have\[\frac{Qq}{a}+\frac{{{q}^{2}}}{a}+\frac{Qq}{a\sqrt{2}}=0\] or\[Q\sqrt{2}+q\sqrt{2}+Q=0\]or\[Q(\sqrt{2}+1)=-q\sqrt{2}\] \[\therefore \]\[Q=-\frac{q\sqrt{2}}{\sqrt{2}+1}=-\frac{2q}{2+\sqrt{2}}\]


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