This question was previously asked in

ISRO (VSSC) Technical Assistant Electronics 2019 Official Paper

Option 2 : 120 V

Subject Test 1: Electrical Basics

3053

20 Questions
80 Marks
30 Mins

__Concept__:

For a series RLC circuit, as shown, the net magnitude/amplitude of the source voltage is given by:

\(V_{net}=\sqrt{V_R^2+(V_L-V_C)^2}\)

V_{R} = Voltage across the resistor

V_{L} = Voltage across the inductor

V_{C} = Voltage across the capacitor

__Analysis__:

At resonance, the net impedance is purely resistive resulting in V_{L} = V_{C}

This is explained as shown:

Given V_{L} = V_{C} = 50 V

V_{R} = 120 V

The net amplitude/magnitude of the source voltage is given by:

\(V_{net}=\sqrt{V_R^2+(V_L-V_L)^2}\)

\(V_{net}=\sqrt{V_R^2}=V_R=120~V\)