Question

AC Voltage applied to a Pure Inductor and a Pure Capacitor in Series (LC Series Circuit).

Answer 1

In this case, voltage across L will lead the current in the circuit by π/2; while the voltage across will lag behind the current by π/2.Thus phase difference between the two voltages is π.

Is the effective reactance of the circuit.

Special Case:

(i) If, in this circuit, X_L = X_C , the amplitude of current in the circuit, would tend to be infinite. It is therefore, the condition of ‘electrical resonance in this circuit.

When X_L = X_C , we have

This frequency value (= f), is called the ‘resonant frequency’ of the given (series) LC circuit.

(ii) If X_L > X_C , the inductive effect dominates. The current lags behind the voltage by a phase angle of π/2 in this a.c circuit. However the peak value, or amplitude of current, increases as effective value of reactance is lower than that of either L or C.

(iii) If X_C > X_L , the capacitive effect dominates. The current leads the voltage by a phase angle of π/2 in the a.c circuit. However the peak value of amplitude, of current increases as the effective value of reactance is lower than that of either L or C.