Combining Series & Parallel in One Circuit

One build that puts series and parallel wiring side by side, so you can see — and measure — the difference with your own multimeter.

You'll need: four LEDs, four resistors, a supply of at least 9V, a breadboard, and a multimeter.

Build two parallel branches across the same supply rails — exactly like Lesson cb-04 — but instead of one LED per branch, put two LEDs in series (Lesson cb-03) within each branch. The result: two independent series pairs, connected to each other in parallel — the same "series-vs-parallel" comparison from Lesson 17, now as a single physical build instead of two separate diagrams.

With it built, use your multimeter to explore what each configuration actually does: measure the total current draw from the supply (it should be roughly double the current of just one branch, since two equal branches share the load). Then measure the voltage across just one LED within a branch, and compare it to the voltage across the whole two-LED branch — you'll see the series voltages adding up exactly as Lesson cb-03 described, entirely independent of what's happening in the other branch.

This dual structure — series strings wired in parallel with each other — is also exactly how larger LED arrays and solar panel installations are commonly built, just scaled up.