Question

The electrostatic force on a small of charge`0.4 mu C` in air is 0.2N. (a) What is the distance between the two spheres ? (b) What is the force on the second sphere due to the first ?

Answer 1

Here `q_(1) = 0.4 mu C = 0.4xx10^(-6) C, q_(2) = -0.8 mu C = -0.8 mu C = -0.8xx10^(-6) C, F = 0.2N , r = ?`
As `F = (q_(1) q_(2))/(4pi in_(0) r^(2)) :. r^(2) = (q_(1) q_(2))/(4pi in_(0) F) or r^(2) = ((0.4xx10^(-6)) (0.8xx10^(-6))xx9xx10^(9))/(0.2)`
`r^(2) = 16xx9xx10^(-4) or r = 4xx3xx10^(-2) m = 0.12 m`
Force on secound sphere due to the first is the same, i.e., 0.2N