Capacitor Lab: Basics
Change plate area, separation and voltage to see capacitance, charge and stored energy.
Change the battery voltage, plate area and separation, or slide the dielectric slab in and out of the capacitor. Drag the top plate to change the gap. Use the voltmeter and the field detector to measure. Disconnect the battery and see charge stay while voltage changes.
About the Capacitor Lab: Basics
Free capacitor lab: basics. Change plate area, separation and voltage to see capacitance, charge and stored energy. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for physics, the capacitor lab: basics 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.
Change plate area, separation and voltage to see capacitance, charge and stored energy. 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 Capacitor Lab: Basics
- Use the controls to change Battery voltage, Plate area, Plate separation, Dielectric slab, Slab position (out → in), and more. The simulation reacts instantly.
- Pick an option such as None, Teflon 2.1, Paper 3.5, Glass 4.7 to switch modes or load an example.
- 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
- Drag the top plate up and down.
- Disconnect the battery and change d.
- Double the plate area.
Key ideas you can learn
- C = ε₀ A / d.
- Charge Q = C V.
- Energy U = ½ C V².
- Moving the plates apart lowers capacitance.
Where this is used in the real world
Camera flashes, touch screens, power supplies and radio tuners use capacitors.
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 does a capacitor do?
It stores energy in the electric field between two plates.
What happens if you disconnect the battery and pull the plates apart?
The charge stays fixed, capacitance falls and the voltage rises.
Is the Capacitor Lab: Basics 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 Capacitor Lab: Basics 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.