There are two particles with charges +Q and +q. The electric force applied to one of the charges is 10 N. Now, +Q is replaced by +4Q while the charge +q is invariant. In addition, the distance between these two charges is doubled. What is the electric force exerted to each particle?

F = 10 N

Explanation:

Assuming that we can treat to both particles as point charges, the magnitude of the force that one charge exerts on the other, must obey Coulomb's Law.The expression for this force, applied  to the charges +Q and +q, separated by a distance d, is as follows:

       

If we replace +Q by +4Q, and d by 2*d, the new expression for the magnitude of the force is as follows:

       

As it can be seen, the force will be as same as before making changes, so F= 10 N.

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