An electric dipole consists of two equal and opposite point charge +Q and -Q, separated by a distance 2l. P is a point collinear with the charges such that its distance from the positive charge is half of its distance from the negative charge. Calculate electric intensity at P.

Explanation

Distance of P from `-Q=d` (say) ,brgt Distance of P from `+Q=d//2`
From fig. `d=d/2+2l`
`d/2=2l`
`d=4l` ...(1)
`E_(1)=(KQ)/((d/2)^(2))=(4KQ)/d^(2)`
`E_(2)=(K(-Q))/d^(2)=(-KQ)/d^(2)`
The electric intensity at P is `E=E_(1)+E_(2)`
`=4 (KQ)/d^(2)-(KQ)/d^(2)implies e=(3KQ)/d^(2)=3xx1/(4 pi epsi_(0)) Q/((4l)^(2))`
`:. E=1/(4pi epsi_(0))(3Q)/(16 l^(2))`