Two charges `q_(1)` and `q_(2)` of `0.1mu mu C` and `-0.1mu mu C` respectively are `10Å` apart. What is the electric field at a point on the line joining them at distance of 10 cm from their mid-point ?

Explanation

Here, `q_(1)=q_(2)=q=0.1mumuC=10^(-13)C` (in magnitude)
Length of the electric dipole formed by these charges
`2a=10Å=10^(-9)m`
Thus, electric dipole moment
`p=2aq=10^(-9)xx10^(-13)=10^(-22)"C-m"`
Distance of the point under consideration on the axial line from the mid - point, `r=10` cm `=0.1` m.
Since, `a lt lt r`, electric field at a point on the axial line
i.e. `E=k_(c)(2p)/(r^(3))`
`rArr" "E=(9xx10^(9))(2xx10^(-22))/((0.1)^(3))" N/C"`
`E=18xx10^(-10)" N/C"`