Coulomb's Law: Force Between Charges
Drag two charges along a ruler, change their size and sign, and see the electric force between them.
Drag either charged ball along the ruler and change the size and sign of each charge. Watch the electric force on each ball, the force-distance graph, and the field along the line. Switch to the atomic scale to see the same law between electrons and protons.
About the Coulomb's Law: Force Between Charges
Free coulomb's law: force between charges. Drag two charges along a ruler, change their size and sign, and see the electric force between them. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for physics, the coulomb's law: force between charges runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Drag two charges along a ruler, change their size and sign, and see the electric force between them. Use it to explore physics ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Coulomb's Law: Force Between Charges
- Use the controls to change Scale, Charge 1, Charge 2, Separation, Force arrows, and more. The simulation reacts instantly.
- Pick an option such as Macro (µC, cm), Atomic (e, nm), Log scale, Linear to switch modes or load an example.
- Press "Flip both signs", "Flip charge 2", "Reset" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Make the charges opposite and watch the arrows.
- Double the distance.
- Set one charge to 0.
Key ideas you can learn
- F = k q₁ q₂ / r².
- Like charges repel and opposite charges attract.
- Doubling the distance makes the force four times smaller.
- Doubling a charge doubles the force.
Where this is used in the real world
Coulomb's law explains chemical bonds, lightning, static shocks and how touch screens sense your finger.
Who is this simulation for?
Physics students in middle school, high school and first-year university, teachers who want a quick demonstration for the projector, and anyone revising for exams. It works well for flipped classrooms because students can explore before the lesson.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What is Coulomb's law?
The electric force between two point charges is proportional to the product of the charges and inversely proportional to the square of the distance.
Are the two forces equal?
Yes. Each charge pulls or pushes the other with the same size of force in opposite directions.
Is the Coulomb's Law: Force Between Charges free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Coulomb's Law: Force Between Charges work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.