Two unit negative charges placed on a straight line. A positive charge q is placed exactly at the mid point between these unit charges. If the system of these three charges is in equilibrium, the value of q (in C) is

Options

A. 1
B. 0.75
C. 0.5
D. 0.25

Answer

(d)

Explanation

Electric potential for three charges in equilibrium is given by ,
`F_(1) + F_(2) = 0 `
`rArr F_(1) = - F_(2) `
`1/4 pi epsilon_(0) (-Q)(-Q)/(2r)^(2) = -1 / 4 pi epsilon_(0)[q(-Q)/r^(2)]`
`rArr Q/4 = q`
`:.` q = 0.25