The force between two point charges is described by Coulomb's Law, which states that the magnitude of the electrostatic force between two point charges is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between their centers. In a vacuum or air, this force can be given by the equation:
F=k‌where:
F is the magnitude of the force between the charges,
q1 and
q2 are the magnitudes of the charges,
r is the distance between the charges,
k is Coulomb's constant (approximately
8.987×109Nm∕C2 in vacuum or air).
When the same arrangement of charges is placed in a medium such as water, the force between the charges is affected by the dielectric constant
(εr) of the medium. The equation for the force in a medium becomes:
F′=‌‌where
εr is the relative permittivity (dielectric constant) of the medium. For water,
εr is approximately 80 at room temperature. Because
εr>1 for any medium other than vacuum, the effect of this is to reduce the force between the charges:
F2=‌Given that
εr>1 for water, this implies that
‌<1, hence
F2<F1. Therefore, the correct statement is:
Option
D:F2<F1