The electrostatic force on a small sphere of charge `0.4muC` due to another small sphere of charge `-0.8muC` in air is 0.2 N. Calculate the distance between two spherical charges, What is the force on the second sphere due to the first?

Explanation

The charges are `q_1=0.4xx10^-6C,`
`q_2=-0.8xx10^-6C`.
Force between the teo charges F = 0.2 N
Force between the charges
`F=1/(4piepsilon_0)(q_1q_2)/r^2`
Distance between two spherical charges is given by
`r^2 = (q_1q_2)/(4piepsilon_0F)`
`=(9xx10^9xx0.4xx10^-6xx0.8xx10^-6)/0.2`
`=16xx9xx10^-4`
`:.r = 4xx3xx10^-2m=0.12m`
Distance between two charges = 0.12 m
Force on second sphere is same `F_2` = 0.2 N.