Electric force between two point charges `q_(1)` and `q_(2)` at rest is F. Now is a charge `-q_(1)` is placed next to `q_(1)`. What will be the (a) force on `q_(2)` due to `q_(1)`(b) total force on `q_(2)` ?

Explanation

(a) As electric force between two body interaction i.e., force between two particles is independent of presence or basence of other particles, the force between `q_(2)` and `q_(1)` will remain unchanged, i.e., F.
(b) An electric force is proportional to the magnitude of charges, therefore total force on `q_(2)` will be given by
`(F.)/(F) = (q_(2)q.)/(q_(2)q_(1)) = (q.)/(q_(1)) = (0)/(q_(1)) = 0` [as `q. = q_(1) + (-q_(1)) = 0`]
Hence, the resultant force on `q_(2)` will be zero.