The Ohm’s Law simulation from PhET lets you adjust the voltage and resistance of a simple circuit and watch the current change. The equation on screen resizes as you drag, so you can see how V, I and R depend on each other instead of just memorising V = IR. It is free, runs in any browser on a phone, tablet or laptop, and it is a great fit for current electricity chapters in Tamil Nadu State Board (Samacheer Kalvi) Science and Physics.
What is the Ohm’s Law simulation?
This interactive simulation shows a simple circuit with a battery and a resistor. You change the voltage and the resistance with sliders, and the current updates straight away. The circuit diagram and the equation change together, with each symbol growing or shrinking as its value changes. Because it runs on HTML5, there is nothing to install, and it works on phones, tablets, Chromebooks and computers.
Middle school to university
Voltage and resistance sliders
Phone, tablet, Chromebook, PC
English
PhET’s learning goals are to predict how the current changes when the voltage changes with resistance kept constant, and how the current changes when the resistance changes with voltage kept constant. It also supports maths topics such as inverse relationships and proportional reasoning.
Launch the Ohm’s Law simulation online
Tap or click inside the player and drag the sliders. Use the full-screen button in the player for a bigger view.
Credit: University of Colorado Boulder
How to use the Ohm’s Law simulation, step by step
- Predict first. Before touching a slider, say what you think will happen to the current.
- Change the voltage only. Keep resistance fixed and raise the voltage. Watch the current rise.
- Change the resistance only. Keep voltage fixed and raise the resistance. Notice that the current falls.
- Watch the equation. The letters grow and shrink to show which values are making the current larger or smaller.
- Test your rule. Double one value and check that the current changes the way you predicted.
Tip for students: change only one slider at a time. That is how scientists find out which variable causes which effect.
The formula behind the simulation: V = I × R
V = I × R ⇒ I = V ÷ R
Here V is the voltage in volts (V), I is the current in amperes (A) and R is the resistance in ohms (Ω). For a fixed resistance, current is directly proportional to voltage. For a fixed voltage, current is inversely proportional to resistance.
Worked example: A 6 V battery is connected across a 200 Ω resistor. The current is I = 6 ÷ 200 = 0.03 A, which is 30 mA. If you double the resistance to 400 Ω, the current drops to 15 mA. Set up the same values in the simulation and compare the readout.
Ohm’s law key terms explained
These are the words you will meet while using the Ohm’s Law simulation, with simple meanings.
Voltage (V)
The push that drives charge around a circuit. Measured in volts (V).
Current (I)
The flow of electric charge. Measured in amperes (A) or milliamperes (mA).
Resistance (R)
How strongly a component opposes the flow of current. Measured in ohms (Ω).
Ohm’s law
For many conductors at constant temperature, the current is proportional to the voltage across them.
Direct proportion
When one quantity doubles, the other doubles too. Current is directly proportional to voltage.
Inverse proportion
When one quantity doubles, the other halves. Current is inversely proportional to resistance.
Milliampere (mA)
One thousandth of an ampere. Small circuits often show current in mA.
Circuit
A closed path that lets current flow from a battery through components and back.
Common mistakes: Mixing up the units (mA and A), saying that more resistance gives more current, and forgetting to convert milliamperes to amperes before using V = IR.
Try the Ohm’s law calculator (practice what you explore)
Enter a voltage and a resistance to see the current. Then tap a “what if” button to see how the change affects the result.
What happens to current when you change a variable
| Change | Effect on current |
|---|---|
| Voltage doubled (R constant) | Current doubles |
| Voltage halved (R constant) | Current halves |
| Resistance doubled (V constant) | Current halves |
| Resistance halved (V constant) | Current doubles |
| Voltage and resistance both doubled | Current stays the same |
Classroom activities for teachers
The Ohm’s Law simulation fits a single 40-minute period.
- Predict and test (10 min): students write a prediction for each slider, then check it in the simulation.
- Proportion hunt (10 min): decide which variable is directly proportional and which is inversely proportional to current.
- Target current (10 min): challenge pairs to reach a chosen current using different voltage and resistance pairs.
- Exit ticket (10 min): students explain in two sentences why a larger resistance gives a smaller current.
Looking for the matching chapters? Browse the Science and Physics books on TN SchoolBooks and download the Samacheer Kalvi PDFs, then use this simulation to make the electricity lessons visual. More free science simulations and textbook PDFs are on the home page.
Quick quiz: test your understanding of Ohm’s law
Score: 0 / 5
Ohm’s Law simulation: frequently asked questions
Is the Ohm’s Law simulation free?
Yes. PhET simulations are free to run online in a browser. Check PhET’s licensing page for reuse terms.
Does it work on a mobile phone?
Yes. It is built with HTML5 and works on phones, tablets and Chromebooks. Use landscape mode or the player’s full-screen button for a bigger view.
What does Ohm’s law say?
Ohm’s law says that for many conductors at constant temperature, the current through them is proportional to the voltage across them. It is written V = IR.
Why does more resistance give less current?
Resistance opposes the flow of charge. With the same voltage, a larger resistance lets less current through, because I = V ÷ R.
The Ohm’s Law simulation turns a formula into something you can drag, test and see. Explore it, take the quiz above, and keep adjusting the sliders until predicting the current feels easy.