Coulomb's Law Sandbox
Place charges anywhere on the canvas and this sandbox draws the forces between them immediately. Because you can drag charges around and watch the arrows resize in real time, the inverse-square dependence stops being an abstract exponent.
How to use this simulation
- Add positive and negative charges and drag them into position
- Change the magnitude of each charge
- Display the net force vector on each charge
What to look for
- Halving the separation quadruples the force
- The forces on any pair are equal and opposite, whatever their relative sizes
- With three or more charges the net force is a genuine vector sum, not a simple total
The physics behind it
Coulomb's law gives the force between two point charges as F = kq₁q₂/r², directed along the line joining them. Like charges repel and unlike attract. With more than two charges, the net force on any one is the vector sum of the individual forces — the superposition principle that underpins all of electrostatics.