Definition
An electrical circuit in which a resistor, inductor, and capacitor are connected end-to-end (in series) and tuned so that, at one specific frequency called the resonant frequency, the inductive reactance and capacitive reactance are equal and cancel each other out. At that frequency the circuit's total opposition (impedance) drops to its minimum value, leaving only the resistance, and current flow through the circuit reaches its maximum.
Plain English
A circuit with a coil and a capacitor wired one after the other that lets the most current pass at one particular frequency. At that frequency the coil and capacitor cancel each other's effects, so the circuit acts like a tuned doorway -- wide open to that frequency and resistant to others.
Context Anchor
Seen in avionics, radio, antenna, and electrical-system discussions, especially when describing tuning or filtering a selected signal frequency.
Derivation
Series means the components are connected one after another in a single path. Resonant comes from the Latin resonare, meaning 'to sound again' or 'echo' -- the same idea as a tuning fork that vibrates strongly at one specific pitch. The circuit 'rings' electrically at one frequency.
Why Pilots Care
Series resonant circuits are the basis for tuning radios and navigation receivers. Understanding them helps explain why a receiver picks up one station clearly while rejecting others, and why a tuned circuit's behavior changes sharply with frequency.
Analogy
Think of pushing a child on a swing. Push at just the right rhythm (the resonant frequency) and the swing goes high with very little effort. Push at the wrong rhythm and you fight the swing. A series resonant circuit is electrically tuned to one rhythm, and current flows freely only at that rhythm.
Intuition Check
Series does not just mean a group of things; here it means electrical parts connected end-to-end so the same current flows through each one. Resonant does not mean the circuit is making sound; it means the circuit responds most strongly at one frequency.
Example Sentence 1
The receiver uses a series resonant circuit to select the desired station while rejecting nearby frequencies.
Example Sentence 2
Technicians adjusted the series resonant circuit until current flow peaked at the desired operating frequency.