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About this tool
Interactive schematic circuit simulator with live electron flow animations, component toggles, and real-time Ohm's Law calculations.
Electric Circuit Builder is an interactive DC circuit schematic that solves Ohm's law live as you change the parts: set the battery from 1 V to 48 V, set two resistors between 1 Ω and 100 Ω each, wire them in series or parallel, and open or close the switch. It computes total resistance (R₁ + R₂ in series, R₁R₂ ÷ (R₁ + R₂) in parallel), current as I = V ÷ R and power as P = V × I, then animates electron flow around the loop and brightens the bulb in proportion to the power dissipated. It is built for students and teachers who want to see cause and effect rather than work through the algebra on paper.
Open Electric Circuit Builder on AltFTool — it loads instantly in your browser.
Under "Circuit Configuration" choose "Series Circuit" or "Parallel Circuit", then drag "Battery Voltage" between 1 and 48 V and the "Resistor R1" and "Bulb Resistance R2" sliders between 1 and 100 ohms.
Use "Close Switch" and "Open Switch" to complete or break the loop — an open switch halts the electron animation on the canvas and the bulb stops glowing.
"Live Multimeter Readout" reports Total Resistance, Current, Power and a Circuit Status of Closed (Flowing) or Open (Broken), recalculated as I = V ÷ R and P = V × I on every change; "Reset" restores the defaults.
Total resistance, current and power are recalculated on every slider move, so the trade-off between them is visible instead of being three separate exercises.
One toggle rewires the same two resistors, which isolates the effect of topology from the effect of changing a component value.
The glow scales with computed watts rather than being decorative, so doubling the voltage visibly does more than doubling the light.
Ohm's law states V = I × R: current equals voltage divided by resistance. With the default 12 V battery and a 10 Ω and 20 Ω resistor in series, total resistance is 30 Ω and the current is 12 ÷ 30 = 0.4 A.
In series resistances simply add, so 10 Ω and 20 Ω give 30 Ω. In parallel the equivalent is R₁R₂ ÷ (R₁ + R₂), so the same pair gives 200 ÷ 30 ≈ 6.7 Ω — always lower than the smaller resistor, which is why parallel wiring draws more current from the same battery.
An open switch breaks the conducting loop, and charge cannot flow unless there is a complete path back to the battery. The readout drops to 0 A and 0 W, and the electron animation halts, regardless of how high the battery voltage is set.
As P = V × I, which is equivalent to I²R. At 12 V with a 30 Ω series total the current is 0.4 A, giving 4.8 W; rewiring the same resistors in parallel raises the current to about 1.8 A and the power to roughly 21.6 W from the same battery.