Vol. IV — Electronics · Tool
Two resistors in series add. Two in parallel share the current and land lower than either alone. Type ohms for two to four parts — Req updates as you type.
Series means one path: the same current walks through every resistor, so the ohms stack. Req = R1 + R2 + … Parallel means each resistor gets its own path from the same two nodes, so more paths lower the total: 1/Req = 1/R1 + 1/R2 + …
Equal resistors in parallel halve (two), divide by three (three), and so on. Unequal ones land closer to the smaller value. Leave R3 or R4 blank to ignore them.
Practice the idea in the Circuit explorer, pick band colors on Resistor codes, or split a supply with a Voltage divider.