Circuit workbench
The Wiring Lab above shows how the real circuits are laid out. Here you change one: pick the loads, the fuse, the wire and the state of the earth, and see what happens to current, voltage at the lamps, wire heating and the fuse. Values are typical of a 12 V motorcycle and simplified for teaching.
Model: lamps and loads as resistances from their 12 V rating (R = V² / P); feed wire R = ρ L / A with copper ρ = 1.68e-8 Ω m; battery as its open-circuit voltage behind an internal resistance; earth and connector resistances in series. Typical values, simplified for teaching.
Things to try
- Turn on the headlight, then make the earth corroded: watch the voltage at the lamp fall and the light dim, the most common electrical fault on old bikes.
- Add the auxiliary lights and heated grips on a 10 A fuse: the fuse blows. Pick the fuse about 25 % above the normal current.
- Run everything on 0.5 mm² wire over 4 m: the wire runs hot and the lamps dim. Thicker or shorter wire fixes both.
- Switch between a charged battery and a running engine: lights are brighter at 14.2 V, because power rises with the square of the voltage.
Circuit Builder
A breadboard for 12 V circuits. Place parts, wire their terminals, then press Test to connect the battery. The circuit is solved with Ohm's law at every node: current shows as moving dots, each part shows its current and power, fuses blow and LEDs burn out. Use the meters as on a real bike, note readings in the log and work through the challenges. Part values are typical examples.