NapkinCalc

Electricity 2 — AC Circuits

Reactance — resistance that depends on frequency

continues from lesson 1 — values defined earlier in the course stay live here

An inductor fights changing current: the faster the change, the harder it fights — X_L grows with frequency. A capacitor is the mirror image: it blocks DC entirely and passes fast changes — X_C shrinks with frequency.

  • X_L = 2π·f·L (Ω, rising)
  • X_C = 1/(2π·f·C) (Ω, falling)
fline:=60Hzf_{line} := 60 Hz = 60 Hz
L1:=50e−3HL_{1} := 50e-3 H = 0.05 H a 50 mH inductor
C1:=20e−6FC_{1} := 20e-6 F = 0.00002 F a 20 µF capacitor
XL=2⋅π⋅fline⋅L1X_{L} = 2 \cdot \pi \cdot f_{line} \cdot L_{1} = 18.85 ohm inductive reactance at 60 Hz
XC=12⋅π⋅fline⋅C1X_{C} = \frac{1}{2 \cdot \pi \cdot f_{line} \cdot C_{1}} = 132.63 ohm capacitive reactance at 60 Hz