RC Circuit & Capacitor Simulator
Charge and discharge a capacitor through a resistor and watch voltage and current change.
Click CHARGE or DISCHARGE (or drag the switch lever) to connect the battery or to short the capacitor through the resistor. Watch the capacitor fill and empty on the graphs.
About the RC Circuit & Capacitor Simulator
Free RC circuit simulation. Flip the switch to charge or discharge a capacitor, change resistance, capacitance and voltage, and see live graphs and the time constant RC. Built for physics, the rc circuit & capacitor simulator 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.
Charge and discharge a capacitor through a resistor and watch voltage and current change. 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 RC Circuit & Capacitor Simulator
- Use the controls to change Battery voltage, Resistance, Capacitance, Time speed, Switch position. The simulation reacts instantly.
- Pick an option such as Charge, Open, Discharge to switch modes or load an example.
- Press "Empty the capacitor" 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
- Click the switch to charge, then flip it to discharge.
- Double the resistance. What happens to the charging time?
- Find the moment the voltage reaches 63% and compare with RC.
- Try a large capacitor and a small one.
Key ideas you can learn
- The time constant is τ = R × C.
- After one τ a charging capacitor reaches about 63% of the battery voltage.
- While discharging, voltage and current both fall exponentially.
Where this is used in the real world
RC circuits control timing in flash cameras, defibrillators, filters in audio equipment and the debounce circuits in every keyboard.
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 the time constant of an RC circuit?
τ = R × C. It is the time for the capacitor to charge to about 63.2% of the supply voltage, or discharge to about 36.8% of its starting value.
Why does current start high when charging?
An empty capacitor acts like a wire, so the full battery voltage sits across the resistor and the current is V/R. As it charges, its voltage opposes the battery and the current falls.
Is the RC Circuit & Capacitor Simulator 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 RC Circuit & Capacitor Simulator 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.