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
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
- [AIEEE 2004]
- A
$ - \frac{Q}{4}(1 + 2\sqrt 2 )$
- B
$\frac{Q}{4}(1 + 2\sqrt 2 )$
- C
$ - \frac{Q}{2}(1 + 2\sqrt 2 )$
- D
$\frac{Q}{2}(1 + 2\sqrt 2 )$
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