X
Components
Xc (100 nF)XL (100 mH)R (10 kΩ)
Xc at f
1.59 kΩ
XL at f
628 Ω
LC resonance f₀
1.59 kHz
Z₀ 1 kΩ · Q 0.1
RC time constant
1 ms
corner 159 Hz
Series RC |Z| at f
10.1 kΩ
phase -9.0°
Engineering Notes
How it works
Reactance is the frequency-dependent "resistance" of capacitors and inductors, measured in ohms. A capacitor's reactance falls with frequency (it passes treble); an inductor's rises (it passes bass). This simple pair of formulas underlies every filter, tone control, coupling network and power-supply choke in a valve amplifier:
Xc = 1 / (2π·f·C) XL = 2π·f·L
Where the two lines cross on the log-log chart, the reactances are equal (the LC resonant frequency), and the characteristic impedance Z₀ sets how sharply a circuit rings:
f₀ = 1 / (2π·√(L·C)) Z₀ = √(L/C) Q = Z₀ / R (series)
A resistor and capacitor form a time constant τ = R·C; the corresponding corner frequency 1/(2πRC) is where Xc equals R. Use this page as a quick bench reference whenever you need to know what a part "looks like" at a given frequency.