To reduce the resonant frequency in an `LCR` series circuit with a generator

Options

A. The generator frequency should be reduced.
B. another capacitor should be added in parallel to the first .
C. the iron core of the inductor should be removed.
D. dielectric in the capacitor should be removed.

Answer

b

Explanation

Resonant frequency in an LCR circuit is given by
`omega = (1)/(sqrt(LC))`
if another capacitor is added in parallel to C, then net capacitance will increases, and hence resonant frequency will decrease, and hence resonant frequency will decrease. If the iron core of the inductor is removed, its self-inductance will decrease, thus increasing the resonant frequency. Also if the to C = `(K epsilon_(0) A)/(d) ( K gt 1 )`, value of C will decreases, thus increasing `omega`.
The resonant frequency is independent of generator frequency.