Ohm's Law Simulator
See Ohm's law come alive. Set the voltage and resistance and watch the current, power, and charge flow update live in an interactive circuit.
Offline ● Works without internet after loading After the first page load, no network connection is needed.This simulation needs a modern browser with canvas support. The measurements and formula below still describe the physics.
Controls
Live measurements
Graph
Formula
I = V / R
Type your own values to solve the formula. The simulation follows along.
- I Current
- —
Observations
What's happening
Real-world examples
LED with a series resistor
A 5 V supply through a 100 ohm resistor limits the current to 0.05 A, keeping an LED safe.
Flashlight bulb
A 3 V cell driving a 6 ohm filament pushes 0.5 A and glows at about 1.5 W.
Near short circuit
Drop the resistance to 2 ohms at 12 V and the current leaps to 6 A, dumping 72 W of heat.
Power scaling
Because P = V times I, halving the resistance at fixed voltage doubles both the current and the power.
Common Questions
What is Ohm's law?
Ohm's law states that the current through a resistor equals the voltage across it divided by its resistance: I = V / R. Voltage (V) is the push, resistance (R) is the opposition, and current (I) is the resulting flow of charge. Rearranged, it also reads V = I times R or R = V / I. The simulator runs this live, so nudging either slider updates the current instantly.
How do voltage and resistance change the current?
Current rises with voltage and falls with resistance. Double the voltage and the current doubles; double the resistance and the current halves. That is the whole content of I = V / R: current is directly proportional to voltage and inversely proportional to resistance. Drag each slider in the simulator and watch the current reading respond in opposite directions.
What is electrical power in the circuit?
Power is the rate at which the resistor turns electrical energy into heat, and it equals voltage times current: P = V times I. Because I = V / R, this is also P = V squared / R, so power climbs steeply as resistance falls. The resistor in the simulator glows brighter as the power rises, which is why a near short circuit is dangerous.
Why does a low resistance draw so much current?
With little to oppose the flow, the same voltage pushes far more charge each second. At 12 V a 2 ohm resistance draws 6 A, while a 100 ohm resistance draws only 0.12 A. The power, P = V times I, rises even faster, so a very low resistance overheats quickly. The simulator shows the carriers speeding up and the resistor glowing as you lower the resistance.
Is the current the same everywhere in the loop?
Yes. In a single series loop the current is the same at every point, because charge is not created or destroyed along the way. The carriers in the simulator move round the whole loop at one speed set by I = V / R. Voltage, by contrast, is dropped across the resistor, which is where the energy is delivered.
Does the simulator send my data anywhere?
No. Everything runs in your browser with a canvas and simple arithmetic. Nothing is uploaded or stored remotely, and the simulator keeps working offline after the page loads.