Batteries and Bulbs
Wire up a battery, bulbs, and a switch and watch the current flow. Try two bulbs, two batteries, and different ways of connecting them to see what changes the brightness.
The bulb and battery buttons toggle between 1 and 2.
| Battery voltage | 1.5 V |
|---|---|
| Total resistance | 3.0 Ω |
| Current from battery | 0.50 A |
| Current per bulb | 0.50 A |
| Bulb brightness | 100% |
With one bulb, series and parallel are the same circuit.
A simplified teaching model.
How to play
Choose "Series" or "Parallel", the number of bulbs, and the number of batteries; the diagram and numbers change. Flip the switch and the dots start or stop moving. Faster dots mean more current. "Run it for me" steps through all 8 combinations.
Learn more
One rule covers it: Ohm's law, voltage = current x resistance. Bulbs in series add their resistances, so the current drops and every bulb dims. Bulbs in parallel each get the full battery voltage, so they stay as bright as a single bulb (the battery just supplies more current in total). Two batteries in series double the voltage. Here each battery is 1.5 V and each bulb is 3 ohms. Brightness is the bulb's power compared with the one-battery, one-bulb circuit (100%). This is a simplified teaching model: it ignores a battery's internal resistance, wire resistance, and the way a hot filament's resistance changes.