Definition
An electrical circuit in which all components are connected end-to-end along a single path, so the same current flows through every component. If the path is broken at any point, current stops everywhere in the circuit.
Plain English
A circuit where everything is wired in a single line, one after another. The electricity has only one route to follow, so if any part fails or is disconnected, the whole circuit stops working.
Context Anchor
Seen in aircraft electrical system discussions, troubleshooting diagrams, and maintenance checks involving switches, lights, resistors, and protective devices.
Derivation
From Latin 'series' meaning 'a row or chain.' The components sit in a chain, one after another, with the current running through each in turn.
Why Pilots Care
A break anywhere in a series circuit disables the entire path, which can affect critical aircraft systems such as lighting or instrumentation.
Analogy
Think of a single-lane road with several toll booths. Every car has to pass through every booth in order. Block one booth and the whole road stops.
Intuition Check
Do not read series as just “several things.” In a series circuit, the key idea is one continuous path through each part, with no alternate route around a failed part.
Example Sentence 1
The technician explained that the old position lights were wired in a series circuit, which is why all three went out when one bulb burned out.
Example Sentence 2
During preflight checks the technician tested the series circuit by measuring voltage drop across each resistor in sequence.