Three charges each of value `q` are placed at the corners of an equilateral triangle. A fourth charge `Q` is placed at the centre of the triangle. If `Q = -q`:

Options

A. the charges will move towards the centre
B. the charges will move away from the centre
C. the charges will remain stationary
D. the charges may move in any direction

Answer

1

Explanation

Let `F = (1)/(4 pi in_(0)).(q^(2))/(L^(2))`
Charge `q(at B)`:
Force due to `q (at C ) : F_(2) = F` , along `CB`
Force due to `Q = -q (at O) : F_(3) = (1)/(4pi in_(0)) (q.q)/(((L)/(sqrt(3)))^(2)) = 3F`
The resultant force on each `q` is towards centre and equal to `(3 - sqrt(3)) F`.