McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 1. |
The main function of a fuse is to |
| A. | protect the line |
| B. | open the circuit |
| C. | protect the appliance |
| D. | prevent excessive currents |
| Answer» D. prevent excessive currents | |
| 2. |
On which of the following routine tests are conducted ? |
| A. | Oil circuit breakers |
| B. | Air blast circuit breakers |
| C. | Minimum oil circuit breakers |
| D. | All of the above |
| Answer» D. All of the above | |
| 3. |
SF6 gas |
| A. | is yellow in colour |
| B. | is lighter than air |
| C. | is nontoxic |
| D. | has pungent small |
| Answer» C. is nontoxic | |
| 4. |
The arcing contacts in a circuit breaker are made of |
| A. | copper tungsten alloy |
| B. | porcelain |
| C. | electrolytic copper |
| D. | aluminium alloy |
| Answer» A. copper tungsten alloy | |
| 5. |
Which of the following medium is employed for extinction of arc in air circuit breaker ? |
| A. | Water |
| B. | Oil |
| C. | Air |
| D. | SF6 |
| Answer» C. Air | |
| 6. |
With which of the following, a circuit breaker must be equipped for remote operation ? |
| A. | Inverse time trip |
| B. | Time-delay trip |
| C. | Shunt trip |
| D. | None of the above |
| Answer» C. Shunt trip | |
| 7. |
Fault diverters are basically |
| A. | fuses |
| B. | relays |
| C. | fast switches |
| D. | circuit breakers |
| Answer» C. fast switches | |
| 8. |
A thermal protection switch can protect against |
| A. | short-circuit |
| B. | temperature |
| C. | overload |
| D. | over voltage |
| Answer» C. overload | |
| 9. |
Arc in a circuit behaves as |
| A. | a capackive reactance |
| B. | an inductive reactance |
| C. | a resistance increasing with voltage rise across the arc |
| D. | a resistance decreasing with voltage rise across the arc |
| Answer» D. a resistance decreasing with voltage rise across the arc | |
| 10. |
Thermal circuit breaker has |
| A. | delayed trip action |
| B. | instantaneous trip action |
| C. | both of the above |
| D. | none of the above |
| Answer» A. delayed trip action | |
| 11. |
Thermal overload relays are used to protect the motor against over current due to |
| A. | short-circuits |
| B. | heavy loads |
| C. | grounds |
| D. | all of the above |
| Answer» B. heavy loads | |
| 12. |
Magnetic circuit breaker has ______ trip action. |
| A. | delayed |
| B. | instantaneous |
| C. | both of the above |
| D. | none of the above |
| Answer» B. instantaneous | |
| 13. |
D.C. shunt relays are made of |
| A. | few turns of thin wire |
| B. | few turns of thick wire |
| C. | many turns of thin wire |
| D. | many turns of thick wire |
| Answer» C. many turns of thin wire | |
| 14. |
The relay operating speed depends upon |
| A. | the spring tension |
| B. | the rate of flux built up |
| C. | armature core air gap |
| D. | all of the above |
| Answer» D. all of the above | |
| 15. |
In order that current should flow without causing excessive heating or voltage drop, the relay contacts should |
| A. | have low contact resistance |
| B. | be clean and smooth |
| C. | be of sufficient size and proper shape |
| D. | have all above properties |
| Answer» D. have all above properties | |
| 16. |
Circuit breakers usually operate under |
| A. | transient state of short-circuit current |
| B. | sub-transient state of short-circuit current |
| C. | steady state of short-circuit current |
| D. | after D.C. component has ceased |
| Answer» A. transient state of short-circuit current | |
| 17. |
Circuit breakers are essentially |
| A. | current carrying contacts called electrodes |
| B. | arc extinguishers |
| C. | circuits to break the system |
| D. | transformers to isolate the two systems |
| Answer» A. current carrying contacts called electrodes | |
| 18. |
The current zero interruption, in oil and air blast circuit breakers, is achieved by |
| A. | lengthening of the gap |
| B. | cooling and blast effect |
| C. | both (A) and (B) |
| D. | deionizing the oil with forced air |
| Answer» C. both (A) and (B) | |
| 19. |
Air blast circuit breaker is used for |
| A. | over currents |
| B. | short duty |
| C. | intermittant duty |
| D. | repeated duty |
| Answer» D. repeated duty | |
| 20. |
An efficient and a well designed protective relaying should have |
| A. | good selectivity and reliability |
| B. | economy and simplicity |
| C. | high speed and selectivity |
| D. | all of the above |
| Answer» D. all of the above | |
| 21. |
Burden of a protective relay is the power |
| A. | required to operate the circuit breaker |
| B. | absorbed by the circuit of relay |
| C. | developed by the relay circuit |
| D. | none of the above |
| Answer» B. absorbed by the circuit of relay | |
| 22. |
Directional relays are based on flow of |
| A. | power |
| B. | current |
| C. | voltage wave |
| D. | all of the above |
| Answer» A. power | |
| 23. |
A differential relay measures the vector difference between |
| A. | two currents |
| B. | two voltages |
| C. | two or more similar electrical quantities |
| D. | none of the above |
| Answer» C. two or more similar electrical quantities | |
| 24. |
A transmission line is protected by |
| A. | inrush protection |
| B. | distance protection |
| C. | time graded and current graded over current protection |
| D. | both (B) and (C) |
| Answer» D. both (B) and (C) | |
| 25. |
Large internal faults are protected by |
| A. | merz price percentage differential protection |
| B. | mho and ohm relays |
| C. | horn gaps and temperature relays |
| D. | earth fault and positive sequence relays |
| Answer» A. merz price percentage differential protection | |
| 26. |
When a transmission line is energized, the wave that propagates on it is |
| A. | current wave only |
| B. | voltage wave only |
| C. | both (A) and (B) |
| D. | power factor wave only |
| Answer» C. both (A) and (B) | |
| 27. |
Protective relays are devices that detect abnormal conditions in electrical circuits by measuring |
| A. | current during abnormal condition |
| B. | voltage during abnormal condition |
| C. | constantly the electrical quantities which differ during normal and abnormal conditions |
| D. | none of the above |
| Answer» C. constantly the electrical quantities which differ during normal and abnormal conditions | |
| 28. |
The voltage appearing across the contacts after opening of the circuit breaker is called______voltage. |
| A. | recovery |
| B. | surge |
| C. | operating |
| D. | arc |
| Answer» A. recovery | |
| 29. |
Ionization in circuit breaker is facilitated by |
| A. | high temperature |
| B. | increase of mean free path |
| C. | increasing field strength |
| D. | all of the above |
| Answer» D. all of the above | |
| 30. |
In a circuit breaker the basic problem is to |
| A. | maintain the arc |
| B. | extinguish the arc |
| C. | transmit large power |
| D. | emit the ionizing electrons |
| Answer» C. transmit large power | |
| 31. |
Overheating of relay contacts or contact born out is due to |
| A. | slow making and breaking of load circuit contacts |
| B. | foreign matter on the contact surface |
| C. | too low contact pressure |
| D. | all of the above |
| Answer» D. all of the above | |
| 32. |
Interruption of large currents by relay requires |
| A. | arc suppressing blow out coils |
| B. | wide separation of the opened contacts |
| C. | high speed opening of contacts |
| D. | all of the above |
| Answer» D. all of the above | |
| 33. |
Shunt capacitance is neglected while considering |
| A. | short transmission line |
| B. | medium transmission line |
| C. | long transmission line |
| D. | medium and long transmission lines |
| Answer» A. short transmission line | |
| 34. |
The arc voltage produced in A.C. circuit breaker is always |
| A. | in phase with the arc current |
| B. | lagging the arc current by 90″ |
| C. | leading the arc current by 90° |
| D. | none of the above |
| Answer» A. in phase with the arc current | |
| 35. |
The time of closing the cycle, in modern circuit breakers is |
| A. | 0.003 sec |
| B. | 0.001 sec |
| C. | 0.01 sec |
| D. | 0.10 sec |
| Answer» A. 0.003 sec | |
| 36. |
Insulation resistance of high voltage circuit breakers is more than |
| A. | 1 mega ohms |
| B. | 10 mega ohms |
| C. | 100 mega ohms |
| D. | 500 mega ohms |
| Answer» C. 100 mega ohms | |
| 37. |
H.R.C. fuses provide best protection against |
| A. | overload |
| B. | reverse current |
| C. | open-circuits |
| D. | short-circuits |
| Answer» D. short-circuits | |
| 38. |
The ground wire should not be smaller than No ______ copper. |
| A. | 2 |
| B. | 4 |
| C. | 6 |
| D. | 10 |
| Answer» D. 10 | |
| 39. |
The delay fuses are used for the protection of ________. |
| A. | motors |
| B. | power outlet circuits |
| C. | fluorescent lamps |
| D. | light circuits |
| Answer» A. motors | |
| 40. |
Which of the following is the least expensive protection for overcurrent is low voltage system ? |
| A. | Rewireable fuse |
| B. | Isolator |
| C. | Oil circuit breaker |
| D. | Air break circuit breaker |
| Answer» A. Rewireable fuse | |
| 41. |
Resistance grounding is used for voltage between |
| A. | 33kVto66kV |
| B. | HkVto33kV |
| C. | 3.3kVandllkV |
| D. | none of the above |
| Answer» C. 3.3kVandllkV | |
| 42. |
The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to |
| A. | lubricate the contacts |
| B. | insulate the contacts from switch body |
| C. | extinguish the arc |
| D. | all of the above |
| Answer» C. extinguish the arc | |
| 43. |
In Railway applications ______ circuit breaker is used. |
| A. | SFe |
| B. | bulk oil |
| C. | minimum oil |
| D. | air break |
| Answer» A. SFe | |
| 44. |
To protect most of the electrical equipment handling low power, the types of relays used are |
| A. | thermocouple |
| B. | electronic and bimetallic |
| C. | both (A) and (B) |
| D. | none of the above |
| Answer» C. both (A) and (B) | |
| 45. |
Wave trap is used to trap waves of |
| A. | power frequencies |
| B. | higher frequencies entering generator or transformer units |
| C. | either of the above |
| D. | none of the above |
| Answer» B. higher frequencies entering generator or transformer units | |
| 46. |
Ungrounded neutral transmission system is not recommended because of system |
| A. | insulation being overstressed due to over voltages |
| B. | insulation overstress may lead to failure and subsequent phase to phase faults |
| C. | being inadequately protected against ground fault |
| D. | all of the above |
| Answer» D. all of the above | |
| 47. |
The reflection co-efficient at the open circuited end of a transmission line. |
| A. | zero |
| B. | infinity |
| C. | unity |
| D. | none of the above |
| Answer» C. unity | |
| 48. |
For the protection of power station buildings against direct strokes the requirements are |
| A. | interception |
| B. | interception and conduction |
| C. | interception, conduction and dissipation |
| D. | interception, conduction, dissipation and reflection |
| Answer» C. interception, conduction and dissipation | |
| 49. |
The interaction between a transmission line and communication line is minimized by |
| A. | transposing transmission as well as communication lines |
| B. | increasing the height of the trans-mission line tower |
| C. | increasing the distance between the two lines |
| D. | all of the above |
| Answer» D. all of the above | |
| 50. |
When a wave propagates on a transmission line, it suffers reflection several times at |
| A. | tapping |
| B. | load end |
| C. | sending end |
| D. | sending and other end |
| Answer» D. sending and other end | |
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