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# Three charges Q, +q ans +q are placed at vertices of equilateral triangle. If total electric potential energy of system is zero, the value of Q will be :

$(A)\;+q \\ (B)\;-q \\ (C)\; +\frac{q}{2} \\ (D)\;-\frac{q}{2}$

Total potential energy = $\large\frac{1}{4 \pi \in _0} \bigg[\large\frac{qq}{r} +\frac{Qq}{r} +\frac{q.q.}{r}\bigg]$
$\qquad=0$
=> $Q= \large\frac{-q}{2}$
Hence D is the correct answer.