Question

which change increases the electric force between objects?
two neutral objects are moved closer together.
electrons are added to two negatively charged objects.
two oppositely charged objects are moved farther apart.
the charge on two positively charged objects is reduced.

Explanation:

• For two neutral objects, there is no electric force initially. Moving them closer doesn't create an electric force.
• According to Coulomb's law \(F = k\frac{q_1q_2}{r^{2}}\) (where \(k\) is a constant, \(q_1\) and \(q_2\) are charges, and \(r\) is the distance between charges). When electrons are added to two negatively - charged objects, the magnitudes of \(q_1\) and \(q_2\) increase. Since \(F\propto q_1q_2\) (when \(r\) is constant), the electric force increases.
• For two oppositely - charged objects, moving them farther apart (\(r\) increases) while \(q_1\) and \(q_2\) are constant. Since \(F=\frac{kq_1q_2}{r^{2}}\), \(F\) decreases as \(r\) increases.
• Reducing the charge (\(q_1\) and \(q_2\)) on two positively - charged objects. Since \(F = k\frac{q_1q_2}{r^{2}}\), \(F\) decreases as \(q_1\) and \(q_2\) decrease.

Answer:

Electrons are added to two negatively charged objects.