Two small nonconducting spheres have a total charge of 90.0 C.

(a) When placed 28.0 cm apart, the force each exerts on the other is 12.0 N and is repulsive. What is the charge on each?
(b) What if the force were attractive?

(a) Smaller charge is and larger charge is .

(b) Smaller charge is and larger charge is .

Explanation:

(a) When both the spheres have same charge then force is repulsive in nature as like charges tend to repel each other.

Therefore, total charge on the two non-conducting spheres will be calculated as follows.

                      =

Therefore, force between the two spheres will be calculated as follows.

        F =

       12 N =

or,    

This means that smaller charge is and larger charge is .

(b)  When force is attractive in nature then it means both the charges are of opposite sign.

Hence, total charge on the non-conducting sphere is as follows.

Now, force between the two spheres is calculated as follows.

    F =

    12 N =

Hence, smaller charge is and larger charge is .