Q51
Allen
LCR SERIES CIRCUIT, RESONANCE
MCQ
The value of quality factor is: $(\omega_0:$ resonating frequency)
A.
$\frac{\omega_0L}{R}$
B.
$\frac{\omega_0}{RC}$
C.
$\sqrt{LC}$
D.
$L / R$
Q52
Allen
LCR SERIES CIRCUIT, RESONANCE
MCQ
If value of R is changed, then :-
A.
Voltage across L remains same
B.
Voltage across C remains same
C.
Voltage across LC combination remains same
D.
Voltage across LC combination changes
Q53
Allen
LCR SERIES CIRCUIT, RESONANCE
MCQ
In a series LCR circuit voltage across resistor, inductor and capacitor are 1V, 3V and 2V respectively. At the instant t when the source voltage is given by: $V = V_{0} \cos \omega t$ , the current in the circuit will be :
A.
$I = I_{0} \cos \left( \omega t + \frac{\pi}{4} \right)$
B.
$I = I_{0} \cos \left( \omega t - \frac{\pi}{4} \right)$
C.
$I = I_{0} \cos \left( \omega t + \frac{\pi}{3} \right)$
D.
$I = I_{0} \cos \left( \omega t - \frac{\pi}{3} \right)$
Q54
Allen
LCR SERIES CIRCUIT, RESONANCE
MCQ
In an AC Circuit decrease in impedance with increase in frequency indicates that circuit has/have :-
A.
Only resistance
B.
Resistance & inductance.
C.
Resistance & capacitance
D.
Resistance, capacitance & inductance.
Q55
Allen
LCR SERIES CIRCUIT, RESONANCE
MCQ
In given LCR circuit, the voltage across the terminals of a resistance & current will be-
A.
400V, 2A
B.
800V, 2A
C.
100V, 2A
D.
100V, 4A
Q56
Allen
LCR SERIES CIRCUIT, RESONANCE
MCQ
Phase of current in LCR circuit ā
A.
Is in the phase of potential
B.
Leading from the phase of potential
C.
Lagging from the phase of potential
D.
Before resonance frequency, leading from the phase of potential and after resonance frequency, lagging from the phase of potential
Q57
Allen
LCR SERIES CIRCUIT, RESONANCE
MCQ
In LCR circuit, the voltage across the terminals of a resistance, inductance & capacitance are 40V, 30V & 60V, then the voltage across the main source will be -
A.
130 volt
B.
100 volt
C.
70 volt
D.
50 volt
Q58
Allen
LCR SERIES CIRCUIT, RESONANCE
MCQ
For an alternating current of frequency $\frac{500}{\pi}\mathrm{Hz}$ in L-C-R series circuit with $L = 1H$ , $C = 1\mu F$ , $R = 100\Omega$ , impedance is :-
A.
$100\Omega$
B.
$100\sqrt{\pi}\Omega$
C.
$100\sqrt{2\pi}\Omega$
D.
$100\pi\Omega$
Q59
Allen
POWER IN AC CIRCUIT
MCQ
A sinusoidal A.C. current flows through a resistor of resistance R. If the peak current is $I_{p}$ , then the power dissipated is :-
A.
$I_{p}^{2}R\cos\theta$
B.
$\frac{1}{2}I_{p}^{2}R$
C.
$\frac{4}{\pi}I_{p}^{2}R$
D.
$\frac{1}{\pi^{2}}I_{p}^{2}R$
Q60
Allen
POWER IN AC CIRCUIT
MCQ
An AC circuit draws 5A at 160 V and the power consumption is 600 W. Then the power factor is:-
A.
1
B.
0.75
C.
0.50
D.
Zero
Q61
Allen
POWER IN AC CIRCUIT
MCQ
Which is not correct for average power P at resonance:
A.
$P=I_{rms} V_{rms}$
B.
$P = \frac{V}{\sqrt{2}} \frac{I}{\sqrt{2}}$
C.
P = VI
D.
$P=I^{2}_{rms} R$
Q62
Allen
POWER IN AC CIRCUIT
MCQ
In an A.C. circuit inductance, capacitance and resistance are connected. If the effective voltage across inductance is $V_{L}$ , across capacitance is $V_{c}$ and across resistance is $V_{R}$ , then the total effective value of voltage is:
A.
$V_{R} + V_{L} + V_{c}$
B.
$V_{R} + V_{L} - V_{c}$
C.
$\sqrt{V_{R}^{2} + (V_{L} - V_{C})^{2}}$
D.
$\sqrt{V_{R}^{2} - (V_{L} - V_{C})^{2}}$
Q63
Allen
POWER IN AC CIRCUIT
MCQ
In an a.c. circuit V and I are given by
V = 100 sin (100 t) volts
I = 100 sin (100t + Ļ/3) mA
The power dissipated in the circuit is
A.
$10^4$ watt
B.
10 watt
C.
2.5 watt
D.
5.0 watt
Q64
Allen
POWER IN AC CIRCUIT
MCQ
For a series LCR circuit the power loss at resonance is:-
A.
$\frac{V^{2}}{\left[\omega L - \frac{1}{\omega C}\right]}$
B.
$I^{2}L\omega$
C.
$I^{2}R$
D.
$\frac{V^{2}}{C\omega}$
Q65
Allen
POWER IN AC CIRCUIT
MCQ
In an alternating circuit applied voltage and current are $E = E_{0} \sin \omega t$ and $I = I_{0} \sin (\omega t + \pi / 2)$ respectively. Then the power consumed in the circuit will be:
A.
Zero
B.
$E_{0}I_{0}/2$
C.
$E_{0}I_{0}/\sqrt{2}$
D.
$E_{0}I_{0}/4$
Q66
Allen
POWER IN AC CIRCUIT
MCQ
In which of the following case power factor will be negligible :-
A.
Inductance and resistance both high
B.
Inductance and resistance both low.
C.
Low resistance and high inductance
D.
High resistance and low inductance
Q67
Allen
POWER IN AC CIRCUIT
MCQ
If V = 100 sin100t volt, and
I = 100 sin(100t + $\frac{\pi}{6}$ ) A. then find the watt
less power in watt :-
A.
$10^{4}$
B.
$10^{3}$
C.
$10^{2}$
D.
$2.5 \times 10^{3}$
Q68
Allen
POWER IN AC CIRCUIT
MCQ
An A.C. supply gives 30V r.m.s. voltage which passes through a 10Ī© resistance. The power dissipated in it is :-
A.
$90\sqrt{2}$ W
B.
90W
C.
$45\sqrt{2}$ W
D.
45 W
Q69
Allen
POWER IN AC CIRCUIT
MCQ
An inductor of inductance L and resistor of resistance R are joined in series and connected by a source of frequency $\omega$ . Power dissipated in the circuit is :-
A.
$\frac{\left(R^{2}+\omega^{2}L^{2}\right)}{V}$
B.
$\frac{V^{2}R}{\left(R^{2}+\omega^{2}L^{2}\right)}$
C.
$\frac{V}{\left(R^{2}+\omega^{2}L^{2}\right)}$
D.
$\frac{\sqrt{R^{2}+\omega^{2}L^{2}}}{V^{2}}$
Q70
Allen
POWER IN AC CIRCUIT
MCQ
For given circuit the power factor is:
A.
0
B.
$1 / 2$
C.
$1 / \sqrt{2}$
D.
None of these
Q71
Allen
POWER IN AC CIRCUIT
MCQ
In a purely capacitive circuit average power dissipated in the circuit is -
A.
$V_{rms}$ $I_{rms}$
B.
Depends on capacitance
C.
Infinite
D.
Zero
Q72
Allen
POWER IN AC CIRCUIT
MCQ
Energy loss in pure capacitance in A.C. circuit is
A.
$\frac{1}{2}CV^{2}$
B.
CV
C.
$\frac{1}{4}CV^{2}$
D.
Zero
Q73
Allen
POWER IN AC CIRCUIT
MCQ
Power dissipated in pure inductance will be :
A.
$\frac{LI^{2}}{2}$
B.
$2LI^{2}$
C.
$\frac{LI^{2}}{4}$
D.
Zero
Q74
Allen
POWER IN AC CIRCUIT
MCQ
The power factor of L-R circuit is:
A.
$\frac{\omega L}{R}$
B.
$\frac{R}{\sqrt{(\omega L)^{2} + R^{2}}}$
C.
$\omega LR$
D.
$\sqrt{\omega LR}$
Q75
Allen
POWER IN AC CIRCUIT
MCQ
If alternating current of rms value 'a' flows through resistance R then power loss in resistance is:
A.
Zero
B.
$a^{2}R$
C.
$\frac{a^{2}R}{2}$
D.
$2a^{2}R$