Coulomb's Law

Definition

Coulomb’s Law quantifies the electrostatic force between charged particles.

It dictates the mathematical scaling of the electromagnetic force, governing everything from atomic radii to molecular interactions.

Coulomb’s Law Formula: The force between two charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
- $F = k \frac{q_1 q_2}{d^2}$ $F = k \frac{q _{1} q _{2}}{d ^{2}}$
  - How to read: “The force F equals k times the quantity q one times q two, all over d squared.”
  - Meaning: Like charges repel, unlike attract; force grows with charge product and falls off as inverse square of separation.
- $k \approx 9 \times 10^9 \text{ N}\cdot\text{m}^2/\text{C}^2$ $k \approx 9 \times 1 0^{9} N \cdot m^{2} / C^{2}$
  - How to read: “The constant k is approximately nine times ten to the ninth newton meters squared per coulomb squared.”
  - Meaning: Coulomb’s constant in SI units—sets the strength scale for electrostatic forces in vacuum.