Four charges equal to $-Q$ are placed at the four corners of a square and a charge $q$ is at its centre. If…

Four charges equal to $-Q$ are placed at the four corners of a square and a charge $q$ is at its centre. If the system is in equilibrium the value of $q$ is
  1. $-\frac{Q}{4}(1+2 \sqrt{2})$
  2. $-\frac{Q}{2}(1+2 \sqrt{2})$
  3. $-\frac{Q}{2}(1+2 \sqrt{2})$
  4. $\frac{Q}{2}(1+2 \sqrt{2})$

Solution

$q=+\frac{Q}{4}(1+2 \sqrt{2})$

Asked in: JEE Main 2004

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