A Level Physics Practice Exam

Which law does the electromagnetic force follow?

1. Inverse cube law

2. Inverse square law

3. Linear law

4. Proportional relationship law

The correct answer is: Inverse square law

The electromagnetic force follows the inverse square law, which states that the strength of this force between two charged objects is inversely proportional to the square of the distance between them. This means that if you double the distance between the charges, the electromagnetic force acting between them becomes one-fourth as strong. This relationship arises from the way electric fields propagate through space. According to Coulomb's law, the force \( F \) between two charges \( q_1 \) and \( q_2 \) is given by the equation: \[ F = k \frac{|q_1 \cdot q_2|}{r^2} \] where \( k \) is Coulomb's constant and \( r \) is the distance between the centers of the two charges. The \( r^2 \) in the denominator clearly illustrates the inverse square nature of the force—it diminishes rapidly as the distance increases. Other laws listed, such as the inverse cube law, would describe forces that decrease with the cube of the distance, which does not apply to electromagnetic interactions. Similarly, linear laws and proportional relationships do not accurately describe how electromagnetic forces behave in relation to distance as they fail to take into account the geometrical spread of electric fields