Old lights wired in series all die when one bulb goes; wired in parallel, each keeps glowing on its own. Series and parallel are the two ways to connect a circuit, and the difference decides what happens when one part fails.
One path or many
In a series circuit, components sit on a single loop — the same current flows through each in turn. In a parallel circuit, components sit on separate branches that share the same voltage. This difference completely changes how a circuit behaves when something breaks.
In a pure series string, one dead bulb breaks the only loop and the whole string goes dark. Wire the bulbs in parallel and each has its own path — one can fail while the rest stay lit. That is why house wiring is parallel.
- Series: one path · same current everywhere · voltage splits among components · one break stops all
- Parallel: multiple paths · same voltage across each branch · current splits · one break leaves others running
- Imagine two identical bulbs and one battery. First wire both bulbs in series.
- Now rewire the same two bulbs in parallel across the battery.
- In which arrangement is each bulb brighter, and why? (Hint: think about the voltage each bulb receives.)
- Predict what happens to the second bulb if the first one burns out, in each arrangement.
What you should see: You reasoned out that parallel bulbs get full voltage (brighter, independent) while series bulbs share voltage (dimmer, all-or-nothing).