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MCQOPTIONS
This section includes 785 Mcqs, each offering curated multiple-choice questions to sharpen your Electronic Devices Circuits knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
A standard sinusoidal current wave changes its polarity at__________. |
| A. | negative value |
| B. | Zero value |
| C. | minimum value |
| D. | maximum value |
| Answer» C. minimum value | |
| 52. |
A resistor and a capacitor are connected in series with a sine wave generator having frequency such that the resistance and the capacitive reactance are the same i.e. voltage across capacitance, VC is equal to Voltage across Resistance, VR. If the frequency of the sine wave generator is doubled, then |
| A. | VR < VC |
| B. | VR = VC |
| C. | VR > VC |
| D. | None of the above |
| Answer» D. None of the above | |
| 53. |
A 50 Hz sinusoidal voltage V = 311 sin ωt is applied to an RL series circuit. If the magnitude of resistance is 5 Ω and that of the inductance is 0.02 H, the r.m.s. value of the steady-state current and the relative phase angle is nearly |
| A. | 19.6 A and 51.5° |
| B. | 27.4 A and -51.5° |
| C. | 19.6 and -51.5° |
| D. | 27.4 A and 51.5° |
| Answer» C. 19.6 and -51.5° | |
| 54. |
An R-L-C series circuit is excited by a DC voltage. If R = 40 Ω, L = 0.2 H, and C = 100 μF, the resulting current response is said to be |
| A. | critically damped |
| B. | undamped |
| C. | over-damped |
| D. | under-damped |
| Answer» E. | |
| 55. |
A sinusoidal wave has a frequency of 50 Hz with 30 A rms current, Which of the following equations represent this wave? |
| A. | i = 42.42 sin 314 t |
| B. | i = 60 sin 25 t |
| C. | i = 30 sin 50 t |
| D. | i = 84.84 sin 25 t |
| Answer» B. i = 60 sin 25 t | |
| 56. |
If y(s) = 1 + s, the network has 1 Ω resistor and |
| A. | 1F capacitor in series |
| B. | 1F capacitor in parallel |
| C. | 1H inductor in series |
| D. | 1H inductor in parallel |
| Answer» D. 1H inductor in parallel | |
| 57. |
A series or parallel RLC circuit is said to be over damped if: |
| A. | α = ωn |
| B. | α > ωn |
| C. | α < ωn |
| D. | 2α = ωn |
| Answer» C. α < ωn | |
| 58. |
If ‘V’ voltage phasor and ‘I’ is current phasor, then VI represents _____. |
| A. | apparent power |
| B. | total power |
| C. | reactive power |
| D. | active power |
| Answer» B. total power | |
| 59. |
If the rms voltage drop across a 15 kΩ resistor is 16 V, the peak current through the resistor is: |
| A. | 15 mA |
| B. | 1.5 mA |
| C. | 10 mA |
| D. | 1 mA |
| Answer» C. 10 mA | |
| 60. |
In the circuit given, the switch is closed at t = 0 +. The initial voltages on the capacitors are indicated in the diagram. The voltages vcl+(t) and Vc2(t) for t ≥ 0 are respectively |
| A. | \(\frac{1}{2} (1-e^{-t} )\) and \(\frac{1}{2} (1+e^{-t} )\) |
| B. | (1 – e-t) and (1 + e-t) |
| C. | \(\frac{1}{2} (1+e^{-t} )\) and \(\frac{1}{2} (1-e^{-t} )\) |
| D. | \(\frac{1}{2} (1+e^{-t} )\) and \( (1+e^{-t/2} )\) |
| Answer» D. \(\frac{1}{2} (1+e^{-t} )\) and \( (1+e^{-t/2} )\) | |
| 61. |
An inductor of 0.5 H inductance and 90 Ω resistance is connected in parallel with a 20 μF capacitor. A voltage of 230 V at 50 Hz is maintained across the circuit. The total power taken from the source is nearly |
| A. | 588 W |
| B. | 145 W |
| C. | 135 W |
| D. | 125 W |
| Answer» C. 135 W | |
| 62. |
An RLC series circuit consisting of R = 4 Ω, inductive reactance = 6 Ω and capacitive reactance = 3 Ω is connected across a 220 v, 50 Hz single-phase AC supply. The power factor of the circuit is: |
| A. | 0.6 leading |
| B. | 0.7 lagging |
| C. | 0.6 lagging |
| D. | 0.8 lagging |
| Answer» E. | |
| 63. |
In an AC circuit with R and L in series which relationship is true |
| A. | the voltage across the inductors and the current through the inductor are in phase |
| B. | the voltage across the inductor lags the current through the inductor by 90 degree |
| C. | the current through the resistor lags the voltage across the inductor by 180 degree |
| D. | the voltage across the resistor lags the voltage across the inductor by 90 degree |
| Answer» E. | |
| 64. |
In a series RL circuit, R = 20 ohms, L = 0.1 H and frequency is 50 Hz. The impedance of the circuit would be doubled by making. |
| A. | R = 40 ohms |
| B. | R = 52.6 ohms |
| C. | R = 67.5 ohms |
| D. | R = 72.5 ohms |
| Answer» D. R = 72.5 ohms | |
| 65. |
In a single phase a.c. circuit, an impedance consists of a resistance and a capacitance. The power factor of the circuit is |
| A. | unity |
| B. | zero |
| C. | leading |
| D. | lagging |
| Answer» D. lagging | |
| 66. |
Determine the frequency of the periodic waveform shown here |
| A. | 20 Hz |
| B. | 200 Hz |
| C. | 10 Hz |
| D. | 50 Hz |
| Answer» D. 50 Hz | |
| 67. |
An RLC series circuit has a resistance of 2 Ω, inductive reactance of 2 Ω and capacitance reactance of 1 Ω when connected across a 200 V, 50 Hz supply. If the frequency of the supply is now changed to 25 Hz, then the power factor of the circuit will be: |
| A. | \(\frac{2}{{\sqrt 5 }}\:leading\) |
| B. | \(\frac{2}{{\sqrt 5 }}\:lagging\) |
| C. | \(\frac{2}{{\sqrt 13 }}\:leading\) |
| D. | \(\frac{2}{{\sqrt 13 }}\:lagging\) |
| Answer» B. \(\frac{2}{{\sqrt 5 }}\:lagging\) | |
| 68. |
________ set(s) of positive and negative values of an alternating quantity is / are known as a cycle. |
| A. | Three complete |
| B. | One complete |
| C. | Two complete |
| D. | Four complete |
| Answer» C. Two complete | |
| 69. |
If two impedances are given as Z1 = 20∠60° and Z2 = 5∠30°, then Z1/Z2 =? |
| A. | 4∠30° |
| B. | 4∠120° |
| C. | 5∠30° |
| D. | 100∠30° |
| Answer» B. 4∠120° | |
| 70. |
Current through and voltage across an element in an AC circuit is given by:i = 10 sin (ωt – 30)v = 100 sin (ωt + 30)The real power consumed by the circuit is: |
| A. | 500 W |
| B. | 250 W |
| C. | 1000 W |
| D. | 750 W |
| Answer» C. 1000 W | |
| 71. |
In a series RLC circuit, R = 1 kΩ, L = 10 μH, C = 1 μF and source voltage = 10 V, the current in the circuit at resonance is |
| A. | 10 mA |
| B. | 5 mA |
| C. | 20 mA |
| D. | 1 mA |
| Answer» B. 5 mA | |
| 72. |
For a zero-mean wave, if the RMS value is 100 V, what is the peak-to-peak amplitude? |
| A. | 140 V |
| B. | 280 V |
| C. | 200 V |
| D. | 70 V |
| Answer» C. 200 V | |
| 73. |
In the circuit shown, if R = 0, then the phase angle between v(t) and i(t) is: |
| A. | 0° |
| B. | 90° |
| C. | 60° |
| D. | 30° |
| Answer» C. 60° | |
| 74. |
e1 = A sin ωt and e2 = B sin (ωt - ϕ), then |
| A. | e1 lags e2 by ϕ |
| B. | e1 is in phase with e2 |
| C. | e2 leads e1 by ϕ |
| D. | None of the above |
| Answer» E. | |
| 75. |
Form factor of a sawtooth waveform with a period of 3 s and a peak voltage of 150 V is: |
| A. | 2.155 |
| B. | 2.555 |
| C. | 1.155 |
| D. | 0.555 |
| Answer» D. 0.555 | |
| 76. |
In a series R-L circuit, R is 10 Ω and L is 20 mH. If the circuit current is 10 sin 314 t A, the phase angle θ between v and i will be |
| A. | tan–1(0.2 π) |
| B. | tan–1(0.4 π) |
| C. | tan–1(0.6 π) |
| D. | tan–1(0.8 π) |
| Answer» B. tan–1(0.4 π) | |
| 77. |
Calculate the form factor of a voltage v = 200 sin (2π60 t). |
| A. | 2.22 |
| B. | infinite |
| C. | 1.11 |
| D. | 0.45 |
| Answer» D. 0.45 | |
| 78. |
Power factor of an A.C. circuit lies between |
| A. | 0 and 1 |
| B. | -1 to 1 |
| C. | 0 and -1 |
| D. | None of these |
| Answer» C. 0 and -1 | |
| 79. |
In the network shown above VS = 4 cos 2t. The value of C is so chosen that the circuit impedance is maximum. Then I1 leads I2 by |
| A. | 45° |
| B. | 90° |
| C. | 135° |
| D. | 153.43° |
| Answer» E. | |
| 80. |
For the circuit given in the figure, the voltage VC (in volts) across the capacitor is |
| A. | \(1.25\sqrt 2 \sin \left( {5{\rm{t}} - 0.25{\rm{\pi }}} \right)\) |
| B. | \(1.25\sqrt 2 \sin \left( {5{\rm{t}} - 0.125{\rm{\pi }}} \right)\) |
| C. | \(2.5\sqrt 2 \sin \left( {5{\rm{t}} - 0.25{\rm{\pi }}} \right)\) |
| D. | \(2.5\sqrt 2 \sin \left( {5{\rm{t}} - 0.125{\rm{\pi }}} \right)\) |
| Answer» D. \(2.5\sqrt 2 \sin \left( {5{\rm{t}} - 0.125{\rm{\pi }}} \right)\) | |
| 81. |
For a series R-C circuit, the power factor corresponding to maximum power is |
| A. | 0.5 lag |
| B. | 0.5 lead |
| C. | 0.707 lag |
| D. | 0.707 lead |
| Answer» E. | |
| 82. |
Average power delivered to impedance (4-j3)Ω by a current 5cos(100πt+100)A |
| A. | 44.2 W |
| B. | 50 W |
| C. | 62.5 W |
| D. | 125 W |
| Answer» C. 62.5 W | |
| 83. |
Consider a series circuit of a resistance and an inductance, both having 5 Ω resistance. A potential difference of 100 V (rms) is applied to it. If applied voltage is 0 V at a certain instant and is increasing then voltage drop across inductive reactance at that instant is: |
| A. | \(20\sqrt 2 \;V\) |
| B. | \(50\;\sqrt 2 \;V\) |
| C. | 50 V |
| D. | 0 V |
| Answer» C. 50 V | |
| 84. |
A power system is providing 250 V AC at 20 A. If the phase angle between current and voltage is 25° then what is the true power used by the system. |
| A. | 2113.8 W |
| B. | 4531.5 W |
| C. | 5517.2 W |
| D. | 11831.6 W |
| Answer» C. 5517.2 W | |
| 85. |
A sinusoidal voltage applied across a series R-C circuit is given by 40sinωt V. The current flowing in the circuit is 20 sin (ωt + 45°) A. Determine the value of average power (in W). |
| A. | 282.84 |
| B. | 286.64 |
| C. | 288.04 |
| D. | 292.24 |
| Answer» B. 286.64 | |
| 86. |
If the voltage across and the current into a certain load or part of the circuit are expressed by I = |I|∠β, respectively. Reactive power (VI*) will be ___________ when the phase angle ∠(α - β) and current is __________ |
| A. | positive, positive |
| B. | negative, negative |
| C. | negative, positive |
| D. | positive, negative |
| Answer» B. negative, negative | |
| 87. |
Determine the total impedance (in ohms) of a series RLC circuit having a resistance of 10 Ohms, Capacitive reactance of 2 Ohms and inductive reactance of 6 ohms, connected in a series across a 200 V, 50 Hz supply. |
| A. | 8.64 |
| B. | 10.77 |
| C. | 12.21 |
| D. | 14.65 |
| Answer» C. 12.21 | |
| 88. |
For which of the following wave, the average value and the RMS value are equal |
| A. | Sinusoidal wave |
| B. | Triangular wave |
| C. | Trapezoidal wave |
| D. | Square wave |
| Answer» E. | |
| 89. |
In an RLC circuit, supplied from an ac source, the reactive power is proportional to the |
| A. | average energy stored in the electric field |
| B. | average energy stored in the magnetic field |
| C. | a sum of the average energy stored in the electric field and that stored in the magnetic field |
| D. | difference between the average energy stored in the electric field and that stored in the magnetic field |
| Answer» E. | |
| 90. |
In LCR circuit which one of the following statements is correct |
| A. | L and R oppose each other |
| B. | R value increases with frequency |
| C. | the inductive reactance increases with frequency |
| D. | the capacitive reactance increases with frequency |
| Answer» D. the capacitive reactance increases with frequency | |
| 91. |
In an A.C. circuit having R and L in series |
| A. | voltage leads the current |
| B. | current leads the voltage |
| C. | voltage and current are in phase |
| D. | none of the above |
| Answer» B. current leads the voltage | |
| 92. |
An alternating voltage is given by the equation \(v = 282.84\sin \left( {377t + \frac{\pi }{6}} \right)\). What is the value of the RMS voltage, frequency, and time period? |
| A. | 20 V, 60 Hz and 0.0167 s |
| B. | 200 V, 50 Hz and 0.02 s |
| C. | 200 V, 60 Hz and 0.0167 s |
| D. | 20 V, 50 Hz and 0.0167 s |
| Answer» D. 20 V, 50 Hz and 0.0167 s | |
| 93. |
If the AC voltage and current are given by the following expressions:V = 200 sin (314t – 60°)I = 50sin (720t), then what is the phase relation between them? |
| A. | Voltage lags current by 60° |
| B. | Voltage and current are in phase |
| C. | Voltage leads current by 60° |
| D. | can’t be determined |
| Answer» E. | |
| 94. |
One of the basic characteristics of any steady state sinusoidal response of a series R - L - C circuit with R, L and C values is |
| A. | the output remains sinusoidal with its frequency being the same as that of the source |
| B. | the output remains sinusoidal with the frequency differing from that of the source |
| C. | the output amplitude equals the source amplitude |
| D. | the phase angle difference between the source and output is zero always |
| Answer» B. the output remains sinusoidal with the frequency differing from that of the source | |
| 95. |
An alternating current varying sinusoidally has a peak value of 50 A and a frequency of 10 Hz Mathematical expression for the current is: |
| A. | i = 50 * √2 sin (2 * π * 10)t |
| B. | \(i = \frac{{50}}{{\sqrt 2 }}\sin \left( {2*\pi *10} \right)t\) |
| C. | \(i = 50*\sqrt 2 \sin \left( {\pi *10} \right)t\) |
| D. | i = 50 sin (2 * π *10)t |
| Answer» E. | |
| 96. |
A 50 Hz current of zero reference has an average value of 45 A. Its instantaneous value at an angle of 30° is: |
| A. | 61 A |
| B. | 22.5 A |
| C. | 32 A |
| D. | 35.33 A |
| Answer» E. | |
| 97. |
An alternating current i is given by i = 141.4 sin 314t A. Find the frequency and time period of the current. |
| A. | f = 50 Hz, T = 0.02 s |
| B. | f = 314 Hz, T = 0.02 s |
| C. | f = 314 Hz, T = (1/314) s |
| D. | f = 50 Hz, T = (1/314) s |
| Answer» B. f = 314 Hz, T = 0.02 s | |
| 98. |
A sine wave has a frequency of 60 Hz. Its angular frequency is: |
| A. | 120 π rad/s |
| B. | 30 π rad/s |
| C. | 60 π rad/s |
| D. | 120/π rad/s |
| Answer» B. 30 π rad/s | |
| 99. |
Power factor of a circuit or installation is defined as: |
| A. | the ratio of power received at the received end to the total power transmitted at the sending end |
| B. | the ratio of power consumed by the circuit in W to the total power at sending end |
| C. | the ratio of the maximum connected load to the total connected load |
| D. | the ratio of power consumed by the circuit in W to the total complex power input to the circuit in VA |
| Answer» E. | |
| 100. |
Elements R, L, and C are connected in parallel. The impedance of the parallel combination can be expressed as\(Z\left( s \right) = \frac{{10s}}{{{s^2} + s + 400}}\)The value of the individual elements R, L and C are |
| A. | 10 Ω, 40 H and 0.1 F |
| B. | 4 Ω, 1 H and 0.1 F |
| C. | 10 Ω, 1 / 40 H and 0.1 F |
| D. | 1 Ω, 40 H and 10 F |
| Answer» D. 1 Ω, 40 H and 10 F | |