= Lossy parallel coil resonance
{title2=$\omega_r^2=1/(LC)-R^2/L^2$}
A <series circuit> comprising <electrical resistance> $R>0$ and <inductance> $L>0$, placed in a <parallel circuit> with <capacitance> $C>0$, has <electrical admittance> $Y=(R+i\omega L)^{-1}+i\omega C$. Vanishing <imaginary part> at nonzero <angular frequency> gives the displayed condition, requiring $L>R^2C$. It defines zero voltage-current <phase difference>, which need not coincide exactly with the maximum of impedance magnitude when loss is present. At this frequency the <electrical impedance> is real and equals $L/(RC)$.
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