This question was previously asked in

VSSC (ISRO) Technician B (Electronic Mechanic) Previous Year Paper (Held on 25 Sept 2016)

Option 1 : Purely resistive circuit

CT 1: Current Affairs (Government Policies and Schemes)

54560

10 Questions
10 Marks
10 Mins

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: