Two identical conducting small spheres are placed with their centers 0.3 m aparts. One is given a charge of 12.0 nC and the other a charge of `-18.0 nC`.
(a) Find the electric force exerted by one sphere on the other?
(b) If the spheres are connected by a conducting wire, find the electric force between the two after they attain equilibrium.

Answer

(a)`=2.16xx10^(-5)N`, (b) `9xx10^(-7)N("repulsive")`

Explanation

(a) `F=(9xx10^(9)xx12xx10^(-9)xx18xx10^(-9))/((0.30)^(2))`
`=2.16xx10^(-5)N("attractive")`
(b) When they are connected by a conducting wire, finally charge on each will be half of total charge wire, finally charge on each will be half of total charge on both. Let q be the final charge on each then `q=(12-18)//2=-3 nC`.
`F'=(9xx10^(9)xx(3xx10^(-9))^(2))/((0.30)^(2))=9xx10^(-7)N("repulsive")`.