To identify the set with the stronger interaction between the two sets of electrically charged objects, the student should ask:
How far apart are the objects in each interaction?
The strength of the electric force between charged objects is influenced by the distance between them, according to Coulomb's Law, which states that the force between two charges is inversely proportional to the square of the distance between them. Thus, knowing how far apart the objects are will help determine the strength of the interaction.