Four positive charges `(2sqrt2-1)Q` are arranged at the four corners of a square. Another charge q is placed at the centre of the square. Resulting force acting on each corner charge is zero if q is

Options

A. `-7Q//4`
B. `-4Q//7`
C. `-Q`
D. none of these

Answer

A

Explanation

`(KqQ)/((a/(sqrt(2)))^(2))=F'+sqrt(2)F`
where `F'=(KQ Q)/((sqrt(2)a)^(2))`
`F=(KQ Q)/((a^(2))`