Electric Field Simulator
How to use the electric field simulator
- Pick an arrangement of charges. Field lines are traced out of each positive charge in the direction a positive test charge would be pushed.
- Change the separation to see the lines between a + and − charge bunch together, or the lines between two like charges push apart.
- Drag on the picture to turn it, scroll or pinch to zoom, and drag with the right button (or two fingers) to move it. Pause stops the clock; Reset starts the simulation again with the current settings.
Frequently asked questions
What do the field lines mean?
A field line points the way a positive test charge would move. Lines start on positive charges and end on negative ones (or go off to infinity), and where they are close together the field is strong.
How is the field calculated?
From Coulomb's law: each charge contributes E = kq ÷ r² pointing away from it (toward it if negative), and the contributions are added as vectors. The simulation follows that total field in small steps to draw each line.
Why does a dipole's field fall off faster than a single charge's?
Far from a dipole the two charges almost cancel, so the field falls as 1 ÷ r³ instead of 1 ÷ r². A quadrupole cancels even better and falls as 1 ÷ r⁴.
It says WebGL is turned off.
The 3D view needs WebGL, which every current browser has. It can be switched off by hardware acceleration being disabled in the browser settings, or by a very old graphics driver. Turn hardware acceleration on, or try another browser.
Is anything uploaded?
No. The simulation is drawn by your own browser with WebGL; nothing is sent anywhere, and it keeps working offline once the page has loaded.