What factors determine the electrostatic force between two objects?

The electrostatic force between two objects depends on two factors.

The first factor is the charge, if the charge of the two objects is large then the magnitude of the electrostatic force between them will also be large.

The second factor is the distance, if the distance between the charge is less the magnitude of electrostatic force will be large vice versa.

We can say that the electrostatic force is directly proportional to charge and inversely proportional to the separation between the charge.