An RLC series resonance boosts:

Question

Question

This question was previously asked in

RRB ALP CBT 2 Electronic Mechanic Previous Paper: Held on 23 Jan 2019 Shift 1

Answer 1

In a series RLC circuit, the impedance is given by

\(Z = \sqrt {{R^2} + {{\left( {{X_L} - {X_C}} \right)}^2}}\)

At resonance, the magnitude of inductive reactance is equal to the magnitude of capacitive reactance.

The magnitude of XL = XC

At this condition, Z = R.

Hence at resonance, the impedance is purely resistive and it is minimum.

Current in the circuit, I = V/Z

As impedance is minimum the current is maximum.

As impedance is purely resistive, the power factor is unity.

Important Points:

In a purely inductive circuit, the current lags the voltage by 90° and the power factor is zero lagging
In a purely capacitive circuit, the current leads the voltage by 90° and the power factor is zero leading

The plot of the frequency response of the series circuit is as shown in the figure:

F1 U.B. Nita 29.10.2019 D 1