Circuit Builder — Free Online Ohm's Law & Circuit Puzzle Game
Circuit Builder uses real nodal analysis — the same mathematical technique used by SPICE circuit simulators — to calculate voltages. Click nodes to connect components and watch live voltage readouts appear across every node and component in the circuit.
The physics behind the game
Ohm's law
The fundamental relationship between voltage, current and resistance. Double the voltage, double the current. Double the resistance, halve the current.
Series resistors
In series, all current flows through each component. Resistances add. Voltage divides proportionally to resistance.
Parallel resistors
In parallel, current splits between paths. Total resistance is less than either individual resistor. Both components see the same voltage.
Kirchhoff's laws
KVL: voltages around any loop sum to zero (energy conservation). KCL: currents into any node sum to zero (charge conservation). These underpin all circuit analysis.