(a) A series LCR circuit is connected to an a.c.
source of variable frequency. Draw a suitable . phasor diagram to deduce the expressions for the amplitude of the current and phase angle.
(b) Obtain the condition at resonance. Draw a plot showing the variation of current with the frequency of a.c. source for two resistances R, and R2 (R1 > R2). Hence define the quality factor, Q and write its role in the tuning of the circuit.