Two point charges `+Q` and `+4 Q` are separated by a distance x . A neutral point is found at a distance r from the weaker charge in between the charges . Express r in terms of x . What are dimensions of electric field ?

Explanation

Suppose P is the neutral point which is at a distance r from +Q charge is
`F_(1) = (1)/(4 pi epsi_(0)) (Qq)/(r^2)`
Force on q due to `+4 Q` charge is `F_(2) = (1)/(4 pi epsi_(0)) (4 Q * q)/(( x-r)^(2))`
P will be neutral point if `F_(1) = F_(2)`
`implies (1)/(4 pi epsi_(0)) (Qq)/(r^(2)) = (1)/(4 pi epsi_(0)) (4 Qq)/((x - r)^(2))`
`implies (x - r)^(2) = 4r^(2)`
`implies x - r = 2 r implies r = x/3`
The dimensions of electric field are `[MLT^(-3) A^(-1)]`