Practical takeaway
Resonance happens when a circuit or antenna is electrically tuned to a particular frequency. It is central to filters, oscillators, tuned circuits and antennas.
Electricity & Electronics
Resonance
Connect capacitance, inductance and frequency to the idea of an electrically tuned circuit.
TECHNICIAN FOUNDATION14 of 16
Technician exam focus
Recognize resonance as a frequency-dependent condition and understand its connection to inductance, capacitance and tuning.
When reactive effects balance
Capacitors and inductors move in opposite directions with frequency.
As frequency rises, XC falls while XL rises.
At resonance, XL = XC.
The inductive and capacitive reactances are equal in magnitude and opposite in effect. In an ideal series RLC circuit they cancel, leaving resistance as the main impedance.
Changing L or C moves the resonant frequency.
That is how tuned circuits select or reject particular frequencies in filters, oscillators, and radio-frequency networks.
Stored energy trades back and forth.
At resonance, energy alternates between the capacitor's electric field and the inductor's magnetic field—the basis of the familiar tuned-circuit “flywheel” effect.
STEMulation
Find the resonant frequency
Resonance
XC at test frequency
XL at test frequency
XC
XL