RC, LR and LC Circuits with D.C. and A.C. Sources

IMPORTANT

RC, LR and LC Circuits with D.C. and A.C. Sources: Overview

This topic covers concepts, such as, Resonance Frequency, Phasor Diagram for Series L-C-R Circuit at Resonance, Discharging Current in R-C Circuit & Electric Circuit etc.

Important Questions on RC, LR and LC Circuits with D.C. and A.C. Sources

EASY
IMPORTANT

A 15.0 μF  capacitor is connected to 220 V, 50 Hz source. The capacitive reactance and the RMS current would be:

HARD
IMPORTANT

A series LCR circuit is made by taking R=100 Ω,L=2πH,C=100πμF . This series combination is connected across an a.c. source of 220 V, 50 Hz. Calculate (i) the impedance of the circuit and
(ii) the peak value of the current flowing in the circuit.
(iii) Calculate the power factor of this circuit.

MEDIUM
IMPORTANT

An a.c. voltage,   V= V m sinωt , is applied across a

(i) Series RC circuit in which the capacitative impedance is ‘a’ times the resistance in the circuit.

(ii) Series RL circuit in which the inductive impedance is ‘b’ times the resistance in the circuit.

Calculate the value of the power factor of the circuit in each case.

EASY
IMPORTANT

An a.c. source, of voltage V=Vm sin ωt, is applied across a series LCR circuit. Which of the following is the phasor diagram for the circuit when capacitative impedance exceeds the inductive impedance?

EASY
IMPORTANT

The instantaneous current and voltage of an AC circuit are given by i=10sin314t A and V=100sin314t V. The power dissipation in the circuit is

HARD
IMPORTANT

A resistor of   200 Ω  and a capacitor of 15.0 μF  are connected in series to a 220 V, 50 Hz a.c. source. Calculate

​(i) The current in the circuit.

(ii) The rms voltage across the resistor and the capacitor.

MEDIUM
IMPORTANT

The instantaneous current and voltage of an a.c. circuit are given by I=10sin300t A and V=200sin300t V. What is the power dissipation in the circuit?

EASY
IMPORTANT

An a.c. voltage of 100 V, 50 Hz is connected across 20 Ω resistor and 2 mH inductor in series. What is the impedance of the circuit?

EASY
IMPORTANT

When an inductor L and a resistor R in series are connected across a 12 V, 50 Hz supply a current of 0.5 A flows in the circuit. The current differs in phase from applied voltage by  π3 radian. The value of R is 

EASY
IMPORTANT

What is the power dissipated in an a.c. circuit in which voltage and current are given by

  V=230sin( ωt+ π 2 )andI=10sinωt?

EASY
IMPORTANT

In a series LCR circuit, the voltage across an inductor, capacitor and resistor are 20 V, 20 V and 40 V respectively. What is the phase difference between the applied voltage and the current in the circuit?

EASY
IMPORTANT

Graph showing variation of current with frequency of AC source in a series LCR circuit is,

HARD
IMPORTANT

An LR series circuit has L=1 H and R=1 Ω. It is connected across an emf of 2 V. The maximum rate which energy is stored in the magnetic field is:

HARD
IMPORTANT

In a circuit shown in the figure, the capacitor C is initially uncharged and the key K is open. In this condition, a current of 1 A flows through the 1 Ω resistor. The key is closed at time t=t0. Which of the following statement(s) is(are) correct?

[Given : e1=0.36]

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HARD
IMPORTANT

Consider an LC circuit, with inductance L=0.1 H and capacitance C=10-3 F, kept on a plane. The area of the circuit is 1 m2. It is placed in a constant magnetic field of strength B0 which is perpendicular to the plane of the circuit. At time t=0, the magnetic field strength starts increasing linearly as B=B0+βt with β=0.04 T s-1. The maximum magnitude of the current in the circuit is____m A.

HARD
IMPORTANT

In the given circuit each of the resistors is of 1 resistance and each of the capacitors has 4μF capacitance. What is the charge in the capacitor between the points B and F?

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HARD
IMPORTANT

100 Ω  resistance is connected in series with a choke coil. When a 400 V, 50 Hz  supply is applied to this combination, the voltage across the resistance and the choke coil are 200 V and 300 V  respectively. Find the power consumed by the choke coil. Also, calculate the power factor of the choke coil and the power factor of the circuit.

MEDIUM
IMPORTANT

In the L-R circuit shown in the figure, the key K is closed at time t=0.

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HARD
IMPORTANT

Initially switch S was closed for long time. Switch is opened at t=0. Take V=12 V, R=4 ohm, C=1.0 μF. At time t=RCln2

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