Seria

Meet Seria, two resistors on a single wire with only one way through.

In a series circuit, components are connected end to end, so there is a single path for charge. The same current must pass through every resistor, and the battery's voltage is shared between them. Each resistor adds its own opposition to the current, so the total resistance is simply the sum: R = R₁ + R₂.

100 Ω and 220 Ω in series make 100 + 220 = 320 Ω. On a 9 V battery the current is I = V/R = 9 / 320 ≈ 0.028 A, about 28 mA. The voltage splits in proportion: about 2.8 V across the 100 Ω resistor and 6.2 V across the 220 Ω.

This sharing is used in voltage dividers, which give a smaller, set voltage from a larger supply, in sensors, and in volume controls.

The weakness of series wiring is that one break stops everything, which is why some older strings of fairy lights went dark when one bulb failed. Household wiring uses parallel circuits so each device works independently. Real batteries also have some internal resistance.