Electrical Resonance
Electrical resonance is said to take place in a series L-C-R circuit when the circuit allows maximum current for a given frequency of the source of alternating supply for which capacitive reactance becomes equal to the inductive reactance. Impedance of this L-C-R circuit is minimum and hence current is maximum.
Resonant circuits are used to respond selectively to signals of a given frequency while discriminating against signals of different frequencies. If the response of the circuit is more narrowly peaked around the chosen frequency, we say that the circuit has higher “selectivity or sharpness”. This sharpness is measures with the help of Q-factor.
In a series L-C-R circuit, the capacitance C is changed to 4 C. To keep the resonant frequency same, the inductance must be changed by
Options:
(a) `2 L`
(b) L/2
(c) `4L`
(d) L/4