Answer:
Decreasing the distance between the particles by a factor of 2
Step-by-step explanation:
To double the force between the two charge particles, the distance between the particles should be reduced by a factor of two.
According to coulombs law "force is directly proportional to the potential between the two charges and inversely proportional to the square of their distances".
F =
F is the electric force
k is the coulomb constant
q is the charge
r is the distance or separation
As the separation between the charges is reduced the force increases and vice versa