A Level Physics Practice Exam

How does the electrostatic force behave as the distance between two charged particles increases?

1. It remains constant

2. It increases

3. It decreases

4. It becomes zero

The correct answer is: It decreases

As the distance between two charged particles increases, the electrostatic force between them decreases due to Coulomb's law. According to this law, the electrostatic force \( F \) between two point charges is inversely proportional to the square of the distance \( r \) between them. The relationship can be expressed as \[ F = k \frac{|q_1 q_2|}{r^2} \] where \( k \) is Coulomb's constant, and \( q_1 \) and \( q_2 \) are the magnitudes of the charges. As the distance \( r \) increases, the denominator of this equation becomes larger, which in turn results in a smaller force. Thus, as the charges are moved further apart, the force decreases significantly, which explains why the correct answer is that the electrostatic force decreases with increasing distance. This behavior is critical in understanding how charged particles interact over distances and is foundational for concepts in electrostatics.