MCQOPTIONS
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MCQOPTIONS
This section includes 188 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of ________ degrees. |
| A. | 0 |
| B. | 0 |
| C. | 5 |
| D. | 0 |
| Answer» D. 0 | |
| 2. |
Form Factor is the ratio of |
| A. | Average value/r.m.s. value |
| B. | Average value/peak value |
| C. | r.m.s. value/average value |
| D. | r.m.s. value/peak value |
| Answer» D. r.m.s. value/peak value | |
| 3. |
Power factor of the following circuit will be zero |
| A. | Resistance |
| B. | Inductance |
| C. | Capacitance |
| D. | Both B and C |
| Answer» E. | |
| 4. |
In series resonant circuit, increasing inductance to its twice value and reducing capacitance to its half value |
| A. | Will change the maximum value of current at resonance |
| B. | Will change the resonance frequency |
| C. | Will change the impedance at resonance frequency |
| D. | Will increase the selectivity of the circuit |
| Answer» E. | |
| 5. |
The power factor of a D.C. circuit is always |
| A. | Less than unity |
| B. | Unity |
| C. | Greater than unity |
| D. | Zero |
| Answer» C. Greater than unity | |
| 6. |
In AC. circuits, laminated iron is invariably used in order to |
| A. | Reduce eddy current loss |
| B. | Increase heat radiation |
| C. | Make assembly cheap and easier |
| D. | Reduce circuit permeability |
| Answer» B. Increase heat radiation | |
| 7. |
At __________ frequencies the parallel R-L circuit behaves as purely resistive. |
| A. | Low |
| B. | Very low |
| C. | High |
| D. | Very high |
| Answer» E. | |
| 8. |
A phasor is |
| A. | A line which represents the magnitude and phase of an alternating quantity |
| B. | A line representing the magnitude and direction of an alternating quantity |
| C. | A colored tag or band for distinction between different phases of a 3-phase supply |
| D. | An instrument used for measuring phases of an unbalanced 3-phase load |
| Answer» B. A line representing the magnitude and direction of an alternating quantity | |
| 9. |
Capacitive susceptance is a measure of |
| A. | Reactive power in a circuit |
| B. | The extent of neutralization of reactive power in a circuit |
| C. | A purely capacitive circuit's ability to pass current |
| D. | A purely capacitive circuit's ability to resist the flow of current |
| Answer» D. A purely capacitive circuit's ability to resist the flow of current | |
| 10. |
Time constant of an inductive circuit |
| A. | Increases with increase of inductance and decrease of resistance |
| B. | Increases with the increase of inductance and the increase of resistance |
| C. | Increases with the decrease of inductance and decrease of resistance |
| D. | Increases with decrease of inductance and increase of resistance |
| Answer» B. Increases with the increase of inductance and the increase of resistance | |
| 11. |
In the case of an unsymmetrical alternating current the average value must always be taken over |
| A. | Unsymmetrical part of the wave form |
| B. | The quarter cycle |
| C. | The half cycle |
| D. | The whole cycle |
| Answer» E. | |
| 12. |
The phase difference between voltage and current wave through a circuit element is given as 30°. The essential condition is that |
| A. | Both waves must have same frequency |
| B. | Both waves must have identical peak values |
| C. | Both waves must have zero value at the same time |
| D. | None of the above |
| Answer» B. Both waves must have identical peak values | |
| 13. |
A sine wave has a frequency of 50 Hz. Its angular frequency is __________ radian/second. |
| A. | 100 n |
| B. | 50 jt |
| C. | 25 JT |
| D. | 5 n |
| Answer» B. 50 jt | |
| 14. |
In a pure capacitive circuit if the supply frequency is reduced to 1/2, the current will |
| A. | Be reduced by half |
| B. | Be doubled |
| C. | Be four times at high |
| D. | Be reduced to one fourth |
| Answer» B. Be doubled | |
| 15. |
In a pure inductive circuit if the supply frequency is reduced to 1/2, the current will |
| A. | Be reduced by half |
| B. | Be doubled |
| C. | Be four times as high |
| D. | Be reduced to one fourth |
| Answer» C. Be four times as high | |
| 16. |
The equation of 50 Hz current sine wave having r.m.s. value of 60 A is |
| A. | 60 sin 25 t |
| B. | 60 sin 50 t |
| C. | 84.84 sin 3141 |
| D. | 42.42 sin 314 t |
| Answer» D. 42.42 sin 314 t | |
| 17. |
Capacitive reactance is more when |
| A. | Capacitance is less and frequency of supply is less |
| B. | Capacitance is less and frequency of supply is more |
| C. | Capacitance is more and frequency of supply is less |
| D. | Capacitance is more and frequency of supply is more |
| Answer» B. Capacitance is less and frequency of supply is more | |
| 18. |
Time constant of a capacitive circuit |
| A. | Increases with the decrease of capacitance and decrease of resistance |
| B. | Increases with the decrease of capacitance and increase of resistance |
| C. | Increases with the increase of capacitance and decrease of resistance |
| D. | Increase with increase of capacitance and increase of resistance |
| Answer» E. | |
| 19. |
A pure capacitor connected across an A.C. voltage consumed 50 W. This is due to |
| A. | The capacitive reactance in ohms |
| B. | The current flowing in capacitor |
| C. | The size of the capacitor being quite big |
| D. | The statement is incorrect |
| Answer» E. | |
| 20. |
For a frequency of 200 Hz, the time period will be |
| A. | 0.05 s |
| B. | 0.005 s |
| C. | 0.0005 s |
| D. | 0.5 s |
| Answer» C. 0.0005 s | |
| 21. |
For a sine wave with peak value Imax the r.m.s. value is |
| A. | 0.5 Imax |
| B. | 0.707 |
| C. | 0.9 |
| D. | 1.414 Imax |
| Answer» C. 0.9 | |
| 22. |
Power factor of the system is kept high |
| A. | To reduce line losses |
| B. | To maximize the utilization of the capacities of generators, lines and transformers |
| C. | To reduce voltage regulation of the line |
| D. | Due to all above reasons |
| Answer» E. | |
| 23. |
The period of a wave is |
| A. | The same as frequency |
| B. | Time required to complete one cycle |
| C. | Expressed in amperes |
| D. | None of the above |
| Answer» C. Expressed in amperes | |
| 24. |
The power factor at resonance in R-L-C parallel circuit is |
| A. | Zero |
| B. | 0.08 lagging |
| C. | 0.8 leading |
| D. | Unity |
| Answer» E. | |
| 25. |
If two sine waves of the same frequency have a phase difference of JT radians, then |
| A. | Both will reach their minimum values at the same instant |
| B. | Both will reach their maximum values at the same instant |
| C. | When one wave reaches its maxi¬mum value, the other will reach its minimum value |
| D. | None of the above |
| Answer» D. None of the above | |
| 26. |
The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVAThe power drawn by the circuit is |
| A. | 12 kW |
| B. | 22 kW |
| C. | 32 kW |
| D. | 64 kW |
| Answer» D. 64 kW | |
| 27. |
In an A.C. circuit power is dissipated in |
| A. | Resistance only |
| B. | Inductance only |
| C. | Capacitance only |
| D. | None of the above |
| Answer» B. Inductance only | |
| 28. |
At very low frequencies a series R-C circuit behaves as almost purely |
| A. | Resistive |
| B. | Inductive |
| C. | Capacitive |
| D. | None of the above |
| Answer» D. None of the above | |
| 29. |
The series and parallel resonance on L-C circuit' differs in that |
| A. | Series resistance needs a low-resistance source for sharp rise in current |
| B. | Series resonance needs a high-resistance source for sharp increase in current |
| C. | Parallel resonance needs a low-resistance source for a sharp increase in impedance |
| D. | Parallel resonance needs a low-resistance source for a sharp rise in line current |
| Answer» B. Series resonance needs a high-resistance source for sharp increase in current | |
| 30. |
Wire-wound resistors are unsuitable for use at high frequencies because they |
| A. | Create more electrical noise |
| B. | Are likely to melt under excessive eddy current heat |
| C. | Consume more power |
| D. | Exhibit unwanted inductive and capacitive effects |
| Answer» E. | |
| 31. |
In a loss-free R-L-C circuit the transient current is |
| A. | Oscillating |
| B. | Square wave |
| C. | Sinusoidal |
| D. | Non-oscillating |
| Answer» D. Non-oscillating | |
| 32. |
If resistance is 20 Q. and inductance is 27 in a R-L series circuit, then time constant of this circuit will be |
| A. | 0.001 s |
| B. | 0.1 s |
| C. | 10 s |
| D. | 100 s |
| Answer» C. 10 s | |
| 33. |
Ohm is unit of all of the following except |
| A. | Inductive reactance |
| B. | Capacitive reactance |
| C. | Resistance |
| D. | Capacitance |
| Answer» E. | |
| 34. |
The frequency of an alternating current is |
| A. | The speed with which the alternator runs |
| B. | The number of cycles generated in one minute |
| C. | The number of waves passing through a point in one second |
| D. | The number of electrons passing through a point in one second |
| Answer» D. The number of electrons passing through a point in one second | |
| 35. |
All definitions of power factor of a series R-L-C circuit are correct except |
| A. | Ratio of net reactance and impedance |
| B. | Ratio of kW and kVA |
| C. | Ratio of J and Z |
| D. | Ratio of W and VA |
| Answer» B. Ratio of kW and kVA | |
| 36. |
The best place to install a capacitor is |
| A. | Very near to inductive load |
| B. | Across the terminals of the inductive load |
| C. | Far away from the inductive load |
| D. | Any where |
| Answer» C. Far away from the inductive load | |
| 37. |
In a circuit containing R, L and C, power loss can take place in |
| A. | C only |
| B. | L only |
| C. | R only |
| D. | All above |
| Answer» D. All above | |
| 38. |
Which of the following statements pertains to resistors only? |
| A. | Can dissipate considerable amount of power |
| B. | Can act as energy storage devices |
| C. | Connecting them in parallel increases the total value |
| D. | Oppose sudden changes in voltage |
| Answer» B. Can act as energy storage devices | |
| 39. |
The power consumed in a circuit element will be least when the phase difference between the current and voltage is |
| A. | 180° |
| B. | 90° |
| C. | 60° |
| D. | 0° |
| Answer» C. 60° | |
| 40. |
Capacitors for power factor correction are rated in |
| A. | kW |
| B. | kVA |
| C. | kV |
| D. | kVAR |
| Answer» E. | |
| 41. |
In a pure resistive circuit |
| A. | Current lags behind the voltage by 90° |
| B. | Current leads the voltage by 90° |
| C. | Current can lead or lag the voltage by 90° |
| D. | Current is in phase with the voltage |
| Answer» E. | |
| 42. |
The ratio of active power to apparent power is known as factor. |
| A. | Demand |
| B. | Load |
| C. | Power |
| D. | Form |
| Answer» D. Form | |
| 43. |
The r.m.s. value of alternating current is given by steady (D.C.) current which when flowing through a given circuit for a given time produces |
| A. | The more heat than produced by A.C. when flowing through the same circuit |
| B. | The same heat as produced by A.C. when flowing through the same circuit |
| C. | The less heat than produced by A.C. flowing through the same circuit |
| D. | None of the above |
| Answer» C. The less heat than produced by A.C. flowing through the same circuit | |
| 44. |
Inductance affects the direct current flow |
| A. | Only at the time of turning off |
| B. | Only at the time of turning on |
| C. | At the time of turning on and off |
| D. | At all the time of operation |
| Answer» D. At all the time of operation | |
| 45. |
Pure inductive circuit |
| A. | Consumes some power on average |
| B. | Does not take power at all from a line |
| C. | Takes power from the line during some part of the cycle and then returns back to it during other part of the cycle |
| D. | None of the above |
| Answer» D. None of the above | |
| 46. |
The frequency of domestic power supply in India is |
| A. | 200 Hz |
| B. | 100 Hz |
| C. | 60 Hz |
| D. | 50 Hz |
| Answer» E. | |
| 47. |
Form factor for a sine wave is |
| A. | 1.414 |
| B. | 0.707 |
| C. | 1.11 |
| D. | 0.637 |
| Answer» D. 0.637 | |
| 48. |
Poor power factor |
| A. | Reduces load handling capability of electrical system |
| B. | Results in more power losses in the electrical system |
| C. | Overloads alternators, transformers and distribution lines |
| D. | Results in all above |
| Answer» E. | |
| 49. |
In a highly capacitive circuit the |
| A. | Apparent power is equal to the actual power |
| B. | Reactive power is more than the apparent power |
| C. | Reactive power is more than the actual power |
| D. | Actual power is more than its reactive power |
| Answer» D. Actual power is more than its reactive power | |
| 50. |
The safest value of current the human body can carry for more than 3 second is |
| A. | 4 mA |
| B. | 9 mA |
| C. | 15 mA |
| D. | 25 mA |
| Answer» C. 15 mA | |