Question T6D08
From subelement T6 - T6D
Which of the following is combined with an inductor to make a resonant circuit?
Why is this correct?
A capacitor is combined with an inductor to create a resonant circuit. These components are energy storage partners: capacitors store energy in electric fields while inductors store energy in magnetic fields. When connected in series or parallel, they create a circuit with a specific resonant frequency where impedance is either very low (series) or very high (parallel). Resistors, Zener diodes, and potentiometers don't create resonance with inductors—they serve different functions like current limiting, voltage regulation, and variable resistance.
Memory tip
Remember the complementary storage pattern: capacitors use electric fields, inductors use magnetic fields. When these two energy storage types combine, they create oscillating energy exchange at a specific frequency—that's resonance. Look for this pairing in tuning and filtering questions.
Learn more
Resonant circuits are fundamental to amateur radio operation, enabling frequency selectivity in receivers, transmitter tuning, and antenna matching networks. The LC resonant frequency formula f = 1/(2π√LC) shows how changing either component value shifts the resonant point. This principle underlies VFO operation, band-pass filters, and antenna tuners that help achieve proper impedance matching for efficient power transfer.
Think about it
Why do you think energy storage components (rather than control components like resistors) are needed to create the oscillating behavior that defines resonance?