Circuit Lab (Ohm's Law)
Wire two resistors in series or parallel and see voltage, current and power.
Drag a resistor sideways to change its resistance. Push the current too high and the resistor will overheat and burn.
About the Circuit Lab (Ohm's Law)
Free circuit simulator. Change battery voltage and resistors, switch between series and parallel, and see current, voltage drops, total resistance and power with animated electrons. Built for physics, the circuit lab (ohm's law) 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.
Wire two resistors in series or parallel and see voltage, current and power. 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 Circuit Lab (Ohm's Law)
- Use the controls to change Wiring, Battery voltage, Resistor R1, Resistor R2. The simulation reacts instantly.
- Pick an option such as Series, Parallel 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
- Switch between series and parallel with the same resistors.
- Raise the voltage and watch the current and power rise.
- Make R1 very small in series and see where the voltage drops.
- Compare total resistance in the two modes.
Key ideas you can learn
- Ohm's law: V = I × R.
- In series the current is the same everywhere and resistances add: R = R1 + R2.
- In parallel the voltage is the same across each branch and 1/R = 1/R1 + 1/R2.
Where this is used in the real world
Every electronic device is a circuit. Electricians, engineers and hobbyists use series and parallel rules to size resistors, fuses and wiring.
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 difference between series and parallel circuits?
In a series circuit there is one path, so the same current flows through every part. In a parallel circuit the current splits between branches, and each branch sees the full battery voltage.
Why does total resistance go down in parallel?
Each extra branch gives the current another path, so overall it is easier for charge to flow. The total is always smaller than the smallest branch.
Is the Circuit Lab (Ohm's Law) 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 Circuit Lab (Ohm's Law) 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.