The resonant frequency of a series LCR circuit with L = 3H, C = 27 μF and R = 20Ω will be:

111 rad/s

The correct answer is Option (1) → 111 rad/s

The resonant frequency $f_0$ (in rad/sec) is given as -

$f_0=\frac{1}{\sqrt{LC}}$

where,

L = Inductance = 3 H

C = Capacitance = 27 μF

$∴f_0=\frac{1}{\sqrt{3×27×10^{-6}}}=\frac{1}{9×10^{-3}}≃111\,rad/sec$