(a) Two insulated charged copper spheres a and b have their centres separated by a distance of 50 cm what is the nutual force of electrostatic repulsion if the charge on each is `6.5 xx10^(-7)` c the radii of a and b negligible compared to the distance of separation
(b) what is the force of repuslion if each spere is charged double the above amount andf the distance between them is haved

Explanation

(a) Required Coulombian force is,
`F = k(q_(A).q_(B))/r^(2)`…..(1)
`=(9 xx 10^(9))(6.5 xx 10^(-7))(6.5 xx 10^(-7))/(0.5)^(2)`
`F = 1.521 xx 10^(-2) N`
(Repulsive because of like charges
(b) New Coulombian force,
`F. = k(q_(A)^(.).q_(B)^(.))/r^(2)`
`=k(2q_(A).2q_(B))/(r/2)^(2)` (As per the statement)
`F. = 16 k(q_(A).q_(B))/r^(2)`
`therefore F. = 16 F` (From eqn (1))
`therefore F. = 1.6 xx 1.521 xx 10^(-2) = 0.2434 N` (Repulsive)