Series and Parallel Circuits

In series the same current flows through every part; in parallel every branch has the same voltage.

Beginner

Series resistors add:

$R_{total} = R_1 + R_2 + \dots$

Parallel resistors add as reciprocals:

$\frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2} + \dots \qquad R_{1\parallel 2} = \frac{R_1 R_2}{R_1 + R_2}$

Two equal resistors in parallel give half the value. The total parallel resistance is always smaller than the smallest branch.

Sub-topics (2)

Two series resistors produce a fraction of the input voltage: Vout = Vin · R2 / (R1 + R2).

Beginner♥ 0🔖 0💬 0

Current splits between parallel branches in inverse proportion to their resistance.

Easy♥ 0🔖 0💬 0

Spotted a mistake or want to add detail? Suggest an improvement — Content Contributors' edits are reviewed by editors before they go live.