# 21.1 RLC Circuits

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## RLC Circuits

AC CIRCUITS
Alternating
Current
ΔV = ΔVmaxsin2πft                    f = frequency

ΔVrms = ΔVmax / √2                    rms voltage

Irms = Imax / √2                           rms current
Resistors P = Irms2 R                                power dissipated

ΔVrms = Irms R                           ΔVmax = ImaxR
Capacitors XC = 1 / 2 π f C                       capacitive reactance

ΔVC,rms = Irms XC

The voltage across a capacitor lags the current by 90°.
Inductors XC = 2 π f L                             inductive reactance

ΔVL,rms = Irms XL

The voltage across an inductor leads the current by 90°.
RLC Series
Circuits
Z = √ R2 + (XL - XC)2               impedance

ΔVrms = Irms Z                          ΔVmax = ImaxZ

Pavg = Irms ΔVrms cosɸ             ɸ = tan-1 (XL - XC / R )

f0 = 1 / 2π √ LC                       resonance frequency