Four charges are arranged at the corners of a square `ABCD`, as shown in the adjoining figure, The force on a positive charge kept at the centre `O` is

Options

A. zero
B. along the diagonal `AC`
C. along the diagonal `BD`
D. perpendicular to side `AB`

Answer

c

Explanation

We put a unit positive charge at `O`. The resultant force due to the charge placed at `A` and `C` is zero and resultant force due to `B` and `D` is towards `D` along the diagonal `BD`