This simulator solves safe, low-voltage ideal circuits. You choose a layout, set the cell voltage and the resistances, and it returns a table of resistance, voltage, current and power for every resistor, plus the steps and three conservation checks.
It is built for reasoning: you can predict the answer first, then use the checks to see whether your method was sound.
How do I use it?
- Choose a layout: all resistors in series, all in parallel, or R1 in series with a parallel pair (R2 and R3).
- Enter the cell voltage in volts. It must be positive.
- Enter R1 and R2 in ohms, both positive. Leave R3 empty to use two resistors, or fill it in for three.
- Press Solve circuit. The mixed layout needs all three resistances, and the tool tells you if one is missing.
- Read the table, the steps, the checks and the text alternative. Reset restores the starting example.
Example walk-through
The tool opens with 6 V, R1 = 2 ohm and R2 = 4 ohm in series. The total resistance is 2 + 4 = 6 ohm, so the current is 6 / 6 = 1 A. The drops are 2 V across R1 and 4 V across R2, and the power is 2 W and 4 W.
The checks agree: 2 + 4 = 6 V equals the cell voltage, the same 1 A flows everywhere, and 6 W supplied equals 2 W + 4 W in the resistors.
Now switch to parallel with the same values. Each resistor has the full 6 V, so R1 carries 3 A and R2 carries 1.5 A.
The cell supplies 4.5 A and the total resistance is about 1.33 ohm, which is smaller than either resistor. Power is 18 W + 9 W = 27 W, which equals 6 × 4.5.
Finally try the mixed layout with R1 = 2, R2 = 4 and R3 = 4 ohm. The parallel pair makes 2 ohm, the total is 4 ohm, and the cell current is 1.5 A. R1 drops 3 V, the pair shares 3 V, and each of R2 and R3 carries 0.75 A.
How do I read the result?
- Table: one row for each resistor, so you can compare voltage and current between components.
- Steps: total resistance first, then total current from V divided by total resistance.
- Conservation checks: voltage, current and energy, each with both sides printed.
- Text alternative: a plain-words description of the circuit you built.
What are the limits?
The model assumes an ideal cell with no internal resistance, ideal wires, fixed resistances and steady direct current. Real components can differ, so the numbers describe the model and not a particular piece of equipment.
Only three layouts are supported, and a zero resistance is rejected because it would be a short circuit. The tool gives no mains wiring or real equipment instructions.
Which lessons explain the output?
Start with using a resistance relationship with units, then current in series and parallel branches. Use circuit symbols consistently when you draw your own diagram, and read explaining a circuit fault for what a reading means on a supplied diagram.
Mixed questions are in the potential difference, resistance and circuits practice set. The other aids are on the tools page.
When you can solve a circuit but cannot explain why, our team can work through your own questions with you. See online one-to-one Physics tuition for how that works.