8.2 Conservation of Electric Charge and the Process of Charging

A point charge is the concept of a charge with no volume. They do not exist in reality but are a good approximation for charged objects with small size. Coulomb’s law describes the electrostatic force between two point charges. For point charges ${q_1}$ and ${q_2}$ separated by a distance r, the magnitude of the electrostatic force is ${|F| = k \frac{q_1q_2}{r^2}}$ where ${k}$ is Coulomb's constant ${8.99 \cdot 10^9 Nm/C^2}$. The direction of the force is along the line connecting the two charges and is attractive if the charges are opposite signs and repulsive if the charges are the same sign.