Definition
An electrical circuit in which an inductor and a capacitor are connected in parallel across a common voltage source, and the values of inductance and capacitance are such that their reactances are equal at a specific frequency known as the resonant frequency. At resonance, the parallel combination presents very high impedance to the source, so very little current flows from the source even though large currents may circulate between the inductor and capacitor.
Plain English
A coil and a capacitor wired side by side that, at one specific frequency, work together to block current from passing through them while energy bounces back and forth between the two parts.
Context Anchor
Seen in aircraft radio, navigation, and avionics discussions, especially when learning how tuned electronic circuits select frequencies.
Derivation
Parallel describes the wiring arrangement (the components share the same two connection points). Resonant comes from the Latin resonare, meaning 'to resound' or 'echo back' -- at the resonant frequency, energy oscillates back and forth between the inductor and capacitor, much like an echo.
Why Pilots Care
Allows precise tuning of navigation and communication radios so the desired frequency is received clearly without interference from adjacent signals.
Analogy
Like a tuning fork that vibrates loudly only when struck at its exact matching note and stays quiet for every other sound.
Grounding Statement
At the resonant frequency, the circuit acts like a closed gate to the outside source, while inside the gate, energy sloshes back and forth between the coil and capacitor.
Intuition Check
Do not read parallel as just meaning two unrelated paths. In this term, it means the inductor and capacitor are connected across the same two points and work together to respond to one selected frequency.
Example Sentence 1
The radio's tuning section uses a parallel resonant circuit to pass the selected frequency to the receiver while blocking all others.
Example Sentence 2
Maintenance adjusted the parallel resonant circuit to eliminate static on the VHF comm radio.