Resonant Frequency Calculator
Calculate the resonant frequency and angular frequency of an LC circuit.
Results
An LC circuit oscillates at its resonant frequency, where the inductive and capacitive reactances cancel out. This principle is used in radio tuners, oscillators and filters. The resonant frequency depends only on the inductance and capacitance values - f = 1/(2π√LC). This calculator also shows the characteristic impedance, which is important for matching and filter design.
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Frequently asked questions
f = 1/(2π√(0.01 × 0.0001)) = 159.15 Hz. This is in the audio frequency range, typical for crossover networks in speakers.
Halving C increases the frequency by √2 (about 1.414x). Going from 100 µF to 50 µF changes the resonant frequency from 159 Hz to 225 Hz.
Z0 = √(L/C). For 10 mH and 100 µF, Z0 = √(0.01/0.0001) = 10 Ω. This determines the voltage-to-current ratio at resonance.
Energy transfers between the magnetic field of the inductor and the electric field of the capacitor. At resonance the reactances are equal (XL = XC), so they cancel and only resistance limits current.
Radio receivers use a variable capacitor with a fixed inductor to select stations. AM radio (530-1710 kHz) uses inductances around 200-300 µH with capacitors of 10-400 pF.