ABSTRACT
Figure 28.1 shows a circuit comprising a coil of inductance L and resistance R connected in series with a capacitor C. The R-L-C series circuit has a total impedance Z given by Z = R + j(XL − XC) ohms, or Z = R + j(ωL − 1/ωC) ohms where ω = 2π f . The circuit is at resonance when (XL − XC) = 0, i.e. when XL = XC or ωL = 1/(ωC). The phasor diagram for this condition is shown in Figure 28.2, where | VL| = |VC |.
