Coulomb's Law Calculator Formula
Understand the math behind the coulomb's law calculator. Each variable explained with a worked example.
Formulas Used
Electrostatic Force
force = 8.9875e9 * abs(q1 * q2) / pow(distance, 2)Variables
| Variable | Description | Default |
|---|---|---|
q1 | Charge 1(C) | 0.000001 |
q2 | Charge 2(C) | 0.000002 |
distance | Distance(m) | 0.05 |
How It Works
Coulomb's Law
Coulomb's law gives the magnitude of the electrostatic force between two point charges.
Formula
F = k * q1 * q2
where k = 8.9875 x 10^9 N·m²/C². Like charges repel, unlike charges attract.
Worked Example
Two charges (1 μC and 2 μC) separated by 5 cm.
- 01F = k * |q1 * q2| / r²
- 02F = 8.9875e9 * |1e-6 * 2e-6| / 0.05²
- 03F = 8.9875e9 * 2e-12 / 0.0025
- 04F = 0.01798 / 0.0025 = 7.19 N
Frequently Asked Questions
How is Coulomb's law similar to Newton's gravitational law?
Both are inverse-square laws. However, gravity is always attractive, while the electric force can attract or repel. The electric force is vastly stronger than gravity.
What is Coulomb's constant?
k = 8.9875 x 10^9 N·m²/C², also written as 1/(4*pi*epsilon_0) where epsilon_0 is the permittivity of free space.
Does the medium between charges matter?
Yes. In a medium with relative permittivity (dielectric constant) kappa, the force is reduced by a factor of kappa.
Ready to run the numbers?
Open Coulomb's Law Calculator