Definition
A direct current (DC) circuit that combines both series and parallel wiring within the same circuit. Some components are connected end-to-end so the same current flows through each (the series portion), while other components are connected across common points so the voltage is the same across each branch (the parallel portion). Total resistance is calculated by reducing the parallel sections to single equivalent resistances, then adding those to the series resistances.
Plain English
A DC circuit that uses a mix of two wiring styles. Part of it is wired in a single line where current has only one path, and part of it is wired so the current splits into branches. The whole circuit works as one, but you analyze it in pieces.
Context Anchor
Seen in aircraft electrical-system training, especially when learning how to read circuit diagrams and troubleshoot lights, motors, relays, and other DC-powered equipment.
Derivation
Series comes from Latin serere, meaning 'to join or link in a row.' Parallel comes from Greek parallelos, meaning 'beside one another.' Together they describe a circuit where some parts are linked in a line and others sit side by side, sharing the same two connection points.
Why Pilots Care
Correct identification prevents misdiagnosis of wiring faults that could disable instruments or emergency power.
Analogy
Think of water moving through pipes. In one section, the water may have to pass through several items in a single line; in another section, it may split into two side paths and then come back together.
Intuition Check
Do not read “series-parallel” as just “a complicated circuit.” It specifically means the circuit contains both one-path connections and branch-path connections.
Example Sentence 1
The cabin lighting system is wired as a series-parallel DC circuit, so a single bulb burning out does not extinguish the entire row.
Example Sentence 2
A short in one parallel leg of the circuit increased current draw on the aircraft battery.