Explore the Electric Potential & Equipotential Lines Lab
Drag a test point around two charges and read its potential and field live, then find where moving along an equipotential line takes zero work.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
Illustration. Open the tool for the real thing.
See it in action
The Electric Potential & Equipotential Lines Lab with sample data entered and the result showing.
What is the Electric Potential & Equipotential Lines Lab?
Drag a test point around two charges and read its potential and field live, then find where moving along an equipotential line takes zero work. It runs in your browser, so a change to a setting or a drag on an object shows up at once.
Engineers map equipotential surfaces to design capacitors, particle accelerators and high-voltage insulation, since components must be shaped to avoid dangerously bunched-up field lines near sharp edges.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
Electric potential from a point charge is V = kQ/r, and potentials from multiple charges simply add (superposition) at any point.
Equipotential lines connect points of equal potential; moving a charge along one does zero work, since W = q(Vfinal - Vinitial) and the potential does not change.
The electric field always points perpendicular to equipotential lines, from higher to lower potential, and is stronger where equipotential lines are packed closer together.
Drag the test point along one of the dashed equipotential rings and watch V barely change.
Find the zero-potential point between two opposite charges.
Move the test point close to one charge and watch the field arrow grow.
Used for
Pick one to see how it fits.
Physics learners
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.
Try it freeTeachers
For teachers: project the Electric Potential & Equipotential Lines Lab on the board, let students predict the result, then run it together and test this: Find the zero-potential point between two opposite charges. For students: change one thing at a time and write down what changes.
Try it freeHow it compares
A plain look at this tool next to the usual alternative.
| This simulation | Textbook diagram | |
|---|---|---|
| Interactive | Drag, tap and change settings | Fixed picture |
| Install | Nothing to install | Not needed |
| Cost | Free to use | Depends on the book |
Questions people ask
Why does moving along an equipotential line take no work?
Work done on a charge by the electric force is W = q(Vfinal - Vinitial); if both points are on the same equipotential line, Vfinal equals Vinitial, so the work done is exactly zero regardless of the path taken between them.
Why is the electric field always perpendicular to equipotential lines?
If the field had any component along an equipotential line, moving a charge along that line would take nonzero work, which would mean the potential was changing along the line - contradicting the definition of an equipotential.
Is the Electric Potential & Equipotential Lines Lab free to use?
Yes. The Electric Potential & Equipotential Lines Lab is free, needs no signup or download and runs in your web browser. It is part of the Physics group of AZRS simulations.
Does the Electric Potential & Equipotential Lines Lab work on a phone or tablet?
Yes. The Electric Potential & Equipotential Lines Lab takes touch input as well as mouse input, so you can use its 3 adjustable settings with a finger. A larger screen makes the controls and graphs easier to read.
How do I use the Electric Potential & Equipotential Lines Lab?
1. In the Electric Potential & Equipotential Lines Lab, use the controls to change Charge Q₁, Charge Q₂, Separation between charges. The simulation reacts instantly. 2. Start with this experiment: Drag the test point along one of the dashed equipotential rings and watch V barely change. Drag any glowing handle, object or slider with your mouse or finger and the Electric Potential & Equipotential Lines Lab responds in real time. 3. Change one setting at a time and watch which readout moves, then compare it with this idea: Electric potential from a point charge is V = kQ/r, and potentials from multiple charges simply add (superposition) at any point.
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Try the Electric Potential & Equipotential Lines Lab now
Drag a test point around two charges and read its potential and field live, then find. Free to use.
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