Category: Electrical Engineering Multiple Choice Questions

RECTIFIERS & CONVERTERS Questions and Answers

1. Which of the following are the applications of D.C. system ?
(a) Battery charging work
(b) Arc welding
(c) Electrolytic and electro-chemical processes
(d) Arc lamps for search lights
(e) All of the above

Answer: e

2. Which of the following methods may be used to convert A.C. system to D.C. ?
(a) Rectifiers
(b) Motor converters
(c) Motor-generator sets
(d) Rotary converters
(e) All of the above

Answer: e

3. In a single phase rotary converter the number of slip rings will be
(a) two
(b) three
(c) four
(d) six
(e) none

Answer: a

4. A synchronous converter can be started
(a) by means of a small auxiliary motor
(b) from AC. side as induction motor
(c) from D.C. side as D.C. motor
(d) any of the above methods
(e) none of the above methods

Answer: d

5. A rotary converter is a single machine with
(a) one armature and one field
(b) two armatures and one field
(c) one armature and two fields
(d) none of the above

Answer: a

6. A rotary converter combines the function of
(a) an induction motor and a D.C. generator
(b) a synchronous motor and a D.C. generator.
(c) a D.C. series motor and a D.C. generator
(d) none of the above

Answer: b

7. Which of the following is reversible in action ?
(a) Motor generator set
(b) Motor converter
(c) Rotary converter
(d) Any of the above
(e) None of the above

Answer: c

8. Which of the following metals is generally manufactured by electrolysis process ?
(a) Load
(b) Aluminium
(c) Copper
(d) Zinc
(e) None of the above

Answer: b

9. With a motor converter it is possible to obtain D.C. voltage only upto
(a) 200-100 V
(6) 600—800 V
(c) 1000—1200 V
(d) 1700—2000 V

Answer: d

10. Normally, which of the following is used, when a large-scale conversion from AC. to D.C. power is required ?
(a) Motor-generator set
(b) Motor converter
(c) Rotary converter
(d) Mercury arc rectifier

Answer: d

11. A rotary converter in general construction and design, is more or less like
(a) a transformer
(b) an induction motor
(c) an alternator
(d) any D.C. machine

Answer: d

12. A rotary converter operates at a
(a) low power factor
(6) high power factor
(c) zero power factor
(d) none of the above

Answer: b

13. In which of the following appUcations, direct current is absolutely essential ?
(a) Illumination
(b) Electrolysis
(c) Variable speed operation
(d) Traction

Answer: b

14. Which of the following AC. motors is usually used in large motor-generator sets?
(a) Synchronous motor
(b) Squirrel cage induction motor
(c) Slip ring induction motor
(d) Any of the above

Answer: a

15. In a rotary converter armature currents are
(a) d.c. only
(b) a.c. only
(c) partly a.c. and partly d.c.

Answer: c

16. In which of the following equipment direct current is needed ?
(a) Telephones
(b) Relays
(c) Time switches
(d) All of the above

Answer: d

17. In a rotary converter I2R losses as compared to a D.C. generator of the same size will be
(a) same
(b) less
(c) double
(d) three times

Answer: b

18. In a mercury arc rectifier positive ions are attracted towards
(a) anode
(b) cathode
(c) shell bottom
(d) mercury pool

Answer: b

19. Mercury, in arc rectifiers, is chosen for cathode because
(a) its ionization potential is relatively low
(b) its atomic weight is quite high
(c) its boiling point and specific heat are low
(d) it remains in liquid state at ordi¬nary temperature
(e) all of the above

Answer: e

20. The ionization potential of mercury is approximately
(a) 5.4 V
(b) 8.4 V
(c) 10.4 V
(d) 16.4 V

Answer: c

21. The potential drop in the arc, in a mercury arc rectifier, varies
(a) 0.05 V to 0.2 V per cm length of the arc
(b) 0.5 V to 1.5 V per cm length of the arc
(c) 2 V to 3.5 V per cm length of the arc
(d) none of the above

Answer: d

22. The voltage drop between the anode and cathode, of a mercury arc rectifier comprises of the following
(a) anode drop and cathode drop
(b) anode drop and arc drop
(c) cathode drop and arc drop
(d) anode drop, cathode drop and arc drop

Answer: d

23. Glass rectifiers are usually made into units capable of D.C. output (maximum continuous rating) of
(a) 100 A at 100 V
(b) 200 A at 200 V
(c) 300 A at 300 V
(d) 400 A at 400 V
(e) 500 A at 500 V

Answer: e

24. The voltage drop at anode, in a mercury arc rectifier is due to
(a) self restoring property of mercury
(b) high ionization potential
(c) energy spent in overcoming the electrostatic field
(d) high temperature inside the rectifier

Answer: c

25. The internal efficiency of a mercury arc rectifier depends on
(a) voltage only
(b) current only
(c) voltage and current
(d) r.m.s. value of current
(e) none of the above

Answer: a

26. If cathode and anode connections in a mercury arc rectifier are inter changed
(a) the rectifier will not operate
(b) internal losses will be reduced
(c) both ion and electron streams will move in the same direction
(d) the rectifier will operate at reduced efficiency

Answer: a

27. The cathdde voltage drop, in a mercury arc rectifier, is due to
(a) expenditure of energy in ionization
(b) surface resistance
(c) expenditure of energy in overcoming the electrostatic field
(d) expenditure of energy in liberating electrons from the mercury

Answer: d

28. To produce cathode spot in a mercury arc rectifier
(a) anode is heated
(b) tube is evacuated
(c) an auxiliary electrode is used
(d) low mercury vapour pressures are used

Answer: c

29. The advantage of mercury arc rectifier is that
(a) it is light in weight and occupies small floor space
(b) it has high efficiency
(c) it has high overload capacity
(d) it is comparatively noiseless
(e) all of the above

Answer: e

30. In a mercury pool rectifier, the voltage drop across its electrodes
(a) is directly proportional to load
(b) is inversely proportional to load
(c) varies exponentially with the load current
(d) is almost independent of load current

Answer: d

RECTIFIERS & CONVERTERS Multiple Choice Questions and Answers

31. In a three-phase mercury arc rectifiers each anode conducts for
(a) one-third of a cycle
(b) one-fourth of a cycle
(c) one-half a cycle
(d) two-third of a cycle

Answer: a

32. In a mercury arc rectifier characteristic blue luminosity is due to
(a) colour of mercury
(b) ionization
(c) high temperature
(d) electron streams

Answer: b

33. Which of the following mercury arc rectifier will deliver least undulating current?
(a) Six-phase
(b) Three-phase
(c) Two-phase
(d) Single-phase

Answer: a

34. In a glass bulb mercury arc rectifier the maximum current rating is restricted to
(a) 2000 A
(b) 1500 A
(c) 1000 A
(d) 500 A

Answer: d

35. In a mercury arc rectifier______ flow from anode to cathode
(a) ions
(b) electrons
(c) ions and electrons
(d) any of the above

Answer: a

36. When a rectifier is loaded which of the following voltage drops take place ?
(a) Voltage drop in transformer reactance
(6) Voltage drop in resistance of transformer and smoothing chokes
(c) Arc voltage drop
(d) All of the above

Answer: d

37. On which of the following factors the number of phases for which a rectifier should be designed depend ?
(a) The voltage regulation of the rec¬tifier should be low
(b) In the output circuit there should be no harmonics
(c) The power factor of the system should be high
(d) The rectifier supply transformer should be utilized to the best ad-vantage
(e) all of the above

Answer: e

38. A mercury arc rectifier possesses ________ regulation characteristics
(a) straight line
(b) curved line
(c) exponential
(d) none of the above

Answer: d

39. It is the_______of the transformer on which the magnitude of angle of overlap depends.
(a) resistance
(b) capacitance
(c) leakage reactance
(d) any of the above

Answer: c

41. In a grid control of mercury arc rectifiers when the grid is made positive relative to cathode, then it the electrons on their may to anode.
(a) accelerates
(b) decelerates
(c) any of the above
(d) none of the above

Answer: a

42. In mercury arc rectifiers having grid, the arc can be struck between anode and cathode only when the grid attains a certain potential, this potential being known as
(a) maximum grid voltage
(b) critical grid voltage
(c) any of the above
(d) none of the above

Answer: b

43. In phase-shift control method the control is carried out by varying the of grid voltage.
(a) magnitude
(b) polarity
(c) phase
(d) any of the above
(e) none of the above

Answer: c

44. In a phase-shift control method, the phase shift between anode and grid voltages can be achieved by means of
(a) shunt motor
(6) synchronous motor
(c) induction regulator
(d) synchronous generator

Answer: c

45. The metal rectifiers are preferred to valve rectifiers due to which of the following advantages ?
(a) They are mechanically strong
(b) They do not require any voltage for filament heating
(c) Both (a) and (b)
(d) None of the above

Answer: c

46. Which of the following statement is incorrect ?
(a) Copper oxide rectifier is a linear device
(b) Copper oxide rectifier is not a perfect rectifier
(c) Copper oxide rectifier has a low efficiency
(d) Copper oxide rectifier finds use in control circuits
(e) Copper oxide rectifier is not stable during early life

Answer: a

47. The efficiency of the copper oxide rectifier seldom exceeds
(a) 90 to 95%
(b) 85 to 90%
(c) 80 to 85%
(d) 65 to 75%

Answer: d

48. Copper oxide rectifier is usually designed not to operate above
(a) 10°C
(b) 20°C
(c) 30°C
(d) 45°C

Answer: d

49. Selenium rectifier can be operated at temperatures as high as
(a) 25°C
(b) 40°C
(c) 60°C
(d) 75°C

Answer: d

50. In selenium rectifiers efficiencies ranging from ______ to ______ percent are attainable
(a) 25, 35
(b) 40, 50
(c) 60, 70
(d) 75, 85

Answer: d

51. Ageing of a selenium rectifier may change the output voltage by
(a) 5 to 10 per cent
(b) 15 to 20 per cent
(c) 25 to 30 per cent
(d) none of the above

Answer: a

52. The applications of selenium rectifiers are usually limited to potential of
(a) 10 V
(b) 30 V
(c) 60 V
(d) 100 V
(e) 200 V

Answer: d

53. Which of the following rectifiers have been used extensively in supplying direct current for electroplating ?
(a) Copper oxide rectifiers
(b) Selenium rectifiers
(c) Mercury arc rectifiers
(d) Mechanical rectifiers
(e) None of the above

Answer: b

54. A commutating rectifier consists of commutator driven by
(a) an induction motor
(b) a synchronous motor
(c) a D.C. series motor
(d) a D.C. shunt motor

Answer: b

55. Which of the following rectifiers are primarily used for charging of low voltage batteries from AC. supply ?
(a) Mechanical rectifiers
(b) Copper oxide rectifiers
(c) Selenium rectifiers
(d) Electrolytic rectifiers
(e) Mercury arc rectifiers

Answer: d

56. The efficiency of an electrolytic rectifier is nearly
(a) 80%
(b) 70%
(c) 60%
(d) 40%

Answer: c

57. Which of the following is the loss within the mercury arc rectifier chamber ?
(a) Voltage drop in arc
(6) Voltage drop at the anode
(c) Voltage drop at the cathode
(d) All of the above

Answer: d

58. The metal rectifiers, as compared to mercury arc rectifiers
(a) operate on low temperatures
(b) can operate on high voltages
(c) can operate on heavy loads
(d) give poor regulation
(e) none of the above

Answer: a

59. In a mercury arc rectifier, the anode is usually made of
(a) copper
(b) aluminium
(c) silver
(d) graphite
(e) tungsten

Answer: d

60. The ignited or auxiliary anode in mercury arc rectifier is made of
(a) graphite
(b) boron carbide
(c) aluminium
(d) copper

Answer: b

TRANSMISSION & DISTRIBUTION Multiple Choice Questions :-

1. By which of the following systems electric power may be transmitted ?
(a) Overhead system
(b) Underground system
(c) Both (a) and (b)
(d) None of the above
Answer: c

2. are the conductors, which connect the consumer’s terminals to the distribution
(a) Distributors
(b) Service mains
(c) Feeders
(d) None of the above
Answer: b

3. The underground system cannot be operated above
(a) 440 V
(b) 11 kV
(c) 33 kV
(d) 66 kV
Answer: d

4. Overhead system can be designed for operation up to
(a) 11 kV
(b) 33 kV
(c) 66 kV
(d) 400 kV
Answer: c

5. If variable part of annual cost on account of interest and depreciation on the capital outlay is equal to the annual cost of electrical energy wasted in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be most economical. This statement is known as
(a) Kelvin’s law
(b) Ohm’s law
(c) Kirchhoffs law
(d) Faraday’s law
(e) none of the above
Answer: a

6. The wooden poles well impregnated with creosite oil or any preservative compound have life
(a) from 2 to 5 years
(b) 10 to 15 years
(c) 25 to 30 years
(d) 60 to 70 years
Answer: c

7. Which of the following materials is not used for transmission and distribution of electrical power ?
(a) Copper
(b) Aluminium
(c) Steel
(d) Tungsten
Answer: d

8. Galvanised steel wire is generally used as
(a) stay wire
(b) earth wire
(c) structural components
(d) all of the above
Answer: d

9. The usual spans with R.C.C. poles are
(a) 40—50 meters
(b) 60—100 meters
(c) 80—100 meters
(d) 300—500 meters
Answer: c

10. The corona is considerably affected by which of the following ?
(a) Size of the conductor
(b) Shape of the conductor
(c) Surface condition of the conductor
(d) All of the above
Answer: d

11. Which of the following are the constants of the transmission lines ?
(a) Resistance
(b) Inductance
(c) Capacitance
(d) All of the above
Answer: d

12. 310 km line is considered as
(a) a long line
(b) a medium line
(c) a short line
(d) any of the above
Answer: a

13. The phenomenon qf rise in voltage at the receiving end of the open-circuited or lightly loaded line is called the
(a) Seeback effect
(b) Ferranti effect
(c) Raman effect
(d) none of the above
Answer: b

14. The square root of the ratio of line impedance and shunt admittance is called the
(a) surge impedance of the line
(b) conductance of the line
(c) regulation of the line
(d) none of the above
Answer: a

15. Which of the following is the demerit of a ‘constant voltage transmission system’ ?
(a) Increase of short-circuit current of the system
(b) Availability of steady voltage at all loads at the line terminals
(c) Possibility of better protection for the line due to possible use of higher terminal reactants
(d) Improvement of power factor at times of moderate and heavy loads
(e) Possibility of carrying increased power for a given conductor size in case of long-distance heavy power transmission
Answer: a

16. Low voltage cables are meant for use up to
(a)l.lkV
(b)3.3kV
(c)6.6kV
(d)llkV
Ans: e

17. The operating voltage of high voltage cables is up to
(a)l.lkV
(b)3.3kV
(c)6.6kV
(d)llkV
Answer: d

18. The operating voltage of supertension cables is up to
(a) 3.3 kV
(b) 6.6 kV
(c) 11 kV
(d) 33 kV
Answer: d

19. The operating voltage of extra high tension cables is upto
(a) 6.6 kV
(b) 11 kV
(c) 33 kV
(d) 66 kV
(e) 132 kV
Answer: d

20. Which of the following methods is used for laying of underground cables ?
(a) Direct laying
(b) Draw-in-system
(c) Solid system
(d) All of the above
Answer: d

21. Which of the following is the source of heat generation in the cables ?
(a) Dielectric losses in cable insulation
(b) losses in the conductor
(c) Losses in the metallic sheathings and armourings
(d) All of the above
Answer: d

22. Due to which of the following reasons the cables should not be operated too hot ?
(a) The oil may loose its viscosity and it may start drawing off from higher levels
(b) Expansion of the oil may cause the sheath to burst
(c) Unequal expansion may create voids in the insulation which will lead to ionization
(d) The thermal instability may rise due to the rapid increase of dielectric losses with temperature
(e) All of the above
Answer: e

23. Which of the following D.C. distribution system is the simplest and lowest in first cost ?
(a) Radial system
(b) Ring system
(c) Inter-connected system
(d) None of the above
Answer: a

24. A booster is a
(a) series wound generator
(b) shunt wound generator
(c) synchronous generator
(d) none of the above
Answer: a

25. Besides a method of trial and error, which of the following methods is employed for solution of network problems in interconnected system ?
(a) Circulating current method
(b) Thevenin’s theorem
(c) Superposition of currents
(d) Direct application of Kirehhoffs laws
(e) All of the above
Ans: e

26. Which of the following faults is most likely to occur in cables ?
(a) Cross or short-circuit fault
(b) Open circuit fault
(c) Breakdown of cable insulation
(d) All of the above
Answer: d

27. The cause of damage to the lead sheath of a cable is
(a) crystallisation of the lead through vibration
(b) chemical action on the lead when buried in the earth
(c) mechanical damage
(d) all of the above
Answer: d

28. The voltage of the single phase supply to residential consumers is
(a) 110 V
(b) 210 V
(c) 230 V
(d) 400 V
Answer: c

29. Most of the high voltage transmission lines in India are
(a) underground
(b) overhead
(c) either of the above
(d) none of the above
Answer: b

30. The distributors for residential areas are
(a) single phase
(b) three-phase three wire
(c) three-phase four wire
(d) none of the above
Answer: c

31. The conductors of the overhead lines are
(a) solid
(b) stranded
(c) both solid and stranded
(d) none of the above
Answer: b

32. High voltage transmission lines use
(a) suspension insulators
(b) pin insulators
(c) both (a) and (b)
(d) none of the above
Answer: a

33. Multicore cables generally use
(a) square conductors
(b) circular conductors
(c) rectangular conductors
(d) sector-shaped conductors
(e) none of the above
Answer: d

34. Distribution lines in India generally use
(a) wooden poles
(b) R.C.C. poles
(c) steel towers
(d) none of the above
Answer: b

35. The material commonly used for insulation in high voltage cables is
(a) lead
(b) paper
(c) rubber
(d) none of the above
Answer: b

36. The loads on distributors systems are generally
(a) balanced
(b) unbalanced
(c) either of the above
(d) none of the above
Answer: b

37. The power factor of industrial loads is generally
(a) unity
(b) lagging
(c) leading
(d) zero
Answer: b

38. Overhead lines generally use
(a) copper conductors
(b) all aluminium conductors
(c) A.C.S.R. conductors
(d) none of these
Answer: c

39. In transmission lines the cross-arms are made of
(a) copper
(b) wood
(c) R.C.C.
(d) steel
Answer: d

40. The material generally used for armour of high voltage cables is
(a) aluminium
(b) steel
(c) brass
(d) copper
Answer: b

41. Transmission line insulators are made of
(a) glass
(b) porcelain
(c) iron
(d) P.V.C.
Answer: b

42. The material commonly used for sheaths of underground cables is
(a) lead
(b) rubber
(c) copper
(d) iron
Answer: a

43. The minimum clearance between the ground and a 220 kV line is about
(a) 4.3 m
(b) 5.5 m
(c) 7.0 m
(d) 10.5 m
Answer: c

44. The spacing between phase conductors of a 220 kV line is approximately equal to
(a) 2 m
(b) 3.5 m
(c) 6 m
(d) 8.5 m
Answer: c

45. Large industrial consumers are supplied electrical energy at
(a) 400 V
(b) 11 kV
(c) 66 kV
(d) 400 kV
Answer: c

46. In a D.C. 3-wire distribution system, balancer fields are cross-connected in order to
(a) boost the generated voltage
(b) balance loads on both sides of the neutral
(c) make both machine^ run as unloaded motors
(d) equalize voltages on the positive and negative outers
Answer: d

47. In a D.C. 3-wire distributor using balancers and having unequal loads on the two sides
(a) both balancers run as generators
(b) both balancers run as motors
(c) balancer connected to lightly- loaded side runs as a motor
(d) balancer connected to heavily- loaded side runs as a motor
Answer: c

48. Transmitted power remaining the same, if supply voltage of a D.C. 2-wire feeder is increased 100 percent, saving in copper is
(a) 25 percent
(b) 50 percent
(c) 75 percent
(d) 100 percent
Answer: b

49. A uniformly-loaded D.C. distributor is fed at both ends with equal voltages. As compared to a similar distributor fed at one end only, the drop at the middle point is
(a) one-fourth
(b) one-third
(c) one-half
(d) twice
(e) none of the above
Answer: a

50. As compared to a 2-wire D.C. distributor, a 3-wire distributor with same maximum voltage to earth uses only
(a) 31.25 percent of copper
(b) 33.3 percent of copper
(c) 66.7 percent of copper
(d) 125 percent of copper
Answer: a

51. Which of the following is usually not the generating voltage ?
(a) 6.6 kV
(b) 8.8 kV
(c) 11 kV
(d) 13.2 kV
Answer: b

52. For an overhead line, the surge impedance is taken as
(a) 20-30 ohms
(b) 70—80 ohms
(c) 100—200 ohms
(d) 500—1000 ohms
(e) none of the above
Answer: c

53. The presence of ozone due to corona is harmful because it
(a) reduces power factor
(b) corrodes the material
(c) gives odour
(d) transfer energy to the ground
(e) none of the above
Answer: b

54. A feeder, in a transmission system, feeds power to
(a) distributors
(b) generating stations
(c) service mains
(d) all of the above
Answer: a

55. The power transmitted will be maximum when
(a) corona losses are minimum
(b) reactance is high
(c) sending end voltage is more
(d) receiving end voltage is more
Answer: c

56. A 3-phase 4 wire system is commonly used on
(a) primary transmission
(b) secondary transmission
(c) primary distribution
(d) secondary distribution
Answer: d

57. Which of the following materials is used for overhead transmission lines ?
(a) Steel cored aluminium
(b) Galvanised steel
(c) Cadmium copper
(d) Any of the above
Answer: d

58. Which of the following is not a constituent for making porcelain insulators ?
(a) Quartz
(b) Kaolin
(c) Felspar
(d) Silica
Answer: d

59. There is a greater possibility of occurence of corona during
(a) dry weather
(b) winter
(c) summer heat
(d) humid weather
(e) none of the above
Answer: d

60. Which of the following relays is used on long transmission lines ?
(a) Impedance relay
(b) Mho’s relay
(c) Reactance relay
(d) None of the above
Answer: b

61. The steel used in steel cored conductors is usually
(a) alloy steel
(b) stainless steel
(c) mild steel
(d) high speed steel
(e) all of the above
Answer: c

62. Which of the following distribution systems is more reliable ?
(a) Radial system
(b) Tree system
(c) Ring main system
(d) All are equally reliable
Answer: c

63. Which of the following characteristics should the line supports for transmission lines possess ?
(a) Low cost
(b) High mechanical strength
(c) Longer life
(d) All of the above
Answer: d

64. Transmission voltage of ll kV is normally used for distances upto
(a) 20—25 km
(b) 40—50 km
(c) 60—70 km
(d) 80—100 km
Answer: a

65. Which of the following regulations is considered best?
(a) 50%
(b) 20%
(c) 10%
(d) 2%
Answer: d

66. Skin effect is proportional to
(a) (conductor diameter)
(b) (conductor diameter)
(c) (conductor diameter)
(d) (conductor diameter)
(e) none of the above
Answer: c

67. A conductor, due to sag between two supports, takes the form of
(a) semi-circle
(b) triangle
(c) ellipse
(d) catenary
Answer: d

68. In AC.S.R. conductors, the insulation between aluminium and steel conductors is
(a) insulin
(b) bitumen
(c) varnish
(d) no insulation is required
Answer: d

69. Which of the following bus-bar schemes has the lowest cost ?
(a) Ring bus-bar scheme
(b) Single bus-bar scheme
(c) Breaker and a half scheme
(d) Main and transfer scheme
Answer: b

70. Owing to skin effect
(a) current flows through the half cross-section of the conductor
(b) portion of the conductor near the surface carries more current and core of the conductor carries less current
(c) portion of the conductor near the surface carries less current and core of the conductor carries more cur¬rent
(d) any of the above
(e) none of the above
Answer: b

71. By which of the following methods string efficiency can be improved ?
(a) Using a guard ring
(b) Grading the insulator
(c) Using long cross arm
(d) Any of the above
(e) None of the above
Answer: d

72. In aluminium conductors, steel core is provided to
(a) compensate for skin effect
(b) neutralise proximity effect
(c) reduce line inductance
(d) increase the tensile strength
Answer: d

73. By which of the following a bus-bar is rated ?
(a) Current only
(b) Current and voltage
(c) Current, voltage and frequency
(d) Current, voltage, frequency and short time current
Answer: d

74. A circuit is disconnected by isolators when
(a) line is energized
(b) there is no current in the line
(c) line is on full load
(d) circuit breaker is not open
Answer: b

75. For which of the following equipment current rating is not necessary ?
(a) Circuit breakers
(b) Isolators
(c) Load break switch
(d) Circuit breakers and load break switches
Answer: b

76. In a substation the following equipment is not installed
(a) exciters
(b) series capacitors
(c) shunt reactors
(d) voltatre transformers
Answer: a

77. jCorona usually occurs when the electrostatic stress in air around the conductor exceeds
(a) 6.6 kV (r.m.s. value)/cm
(b) 11 kV (r.m.s. value)/cm
(c) 22 kV (maximum value)/cm
(d) 30 kV (maximum value)/cm
Answer: d

78. The voltage drop, for constant voltage transmission is compensated by installing
(a) inductors
(b) capacitors
(c) synchronous motors
(d) all of above
(e) none of the above
Answer: c

79. The use of strain type insulators is made where the conductors are
(a) dead ended
(b) at intermediate anchor towers
(c) any of the above
(d) none of the above
Answer: c

80. The current drawn by the line due to corona losses is
(a) non-sinusoidal
(b) sinusoidal
(c) triangular
(d) square
Answer: a

81. Pin type insulators are generally not used for voltages beyond
(a) 1 kV
(b) 11 kV
(c) 22 kV
(d) 33 kV
Answer: d

82. Aluminium has a specific gravity of
(a) 1.5
(b) 2.7
(c) 4.2
(d) 7.8
Answer: b

83. For transmission of power over a distance of 200 km, the transmission voltage should be
(a) 132 kV
(b) 66 kV
(c) 33 kV
(d) 11 kV
Answer: a

84. For aluminium, as compared to copper, all the following factors have higher values except
(a) specific volume
(6) electrical conductivity
(c) co-efficient of linear expansion
(d) resistance per unit length for same cross-section
Answer: b

85. Which of the following equipment, for regulating the voltage in distribution feeder, will be most economical ?
(a) Static condenser
(b) Synchronous condenser
(c) Tap changing transformer
(d) Booster transformer
Answer: d

86. In a tap changing transformer, the tappings are provided on
(a) primary winding
(b) secondary winding
(c) high voltage winding
(d) any of the above
Answer: c

87. Constant voltage transmission entails the following disadvantage
(a) large conductor area is required for same power transmission
(b) short-circuit current of the system is increased
(c) either of the above
(d) none of the above
Answer: b

88. On which of the following factors skin effect depends ?
(a) Frequency of the current
(b) Size of the conductor
(c) Resistivity of the conductor material
(d) All of the above
Answer: d

89. The effect of corona can be detected by
(a) presence of ozone detected by odour
(b) hissing sound
(c) faint luminous glow of bluish colour
(d) all of the above
Answer: d

90. For transmission of power over a distance of 500 km, the transmission voltage should be in the range
(a) 150 to 220 kV
(b) 100 to 120 kV
(c) 60 to 100 kV
(d) 20 to 50 kV
Answer: a

91. In the analysis of which of the following lines shunt capacitance is neglected ?
(a) Short transmission lines
(b) Medium transmission lines
(c) Long transmission lines
(d) Medium as well as long transmission lines
Answer: a

92. When the interconnector between two stations has large reactance
(a) the transfer of power will take place with voltage fluctuation and noise
(b) the transfer of power will take place with least loss
(c) the stations will fall out of step be¬cause of large angular displacement between the stations
(d) none of the above
Answer: c

93. The frequency of voltage generated, in case of generators, can be increased by
(a) using reactors
(b) increasing the load
(c) adjusting the governor
(d) reducing the terminal voltage
(e) none of the above
Answer: c

94. When an alternator connected to the bus-bar is shut down the bus-bar voltage will
(a) fall
(b) rise
(c) remain unchanged
(d) none of the above
Answer: c

95. The angular displacement between two interconnected stations is mainly due to
(a) armature reactance of both alternators
(b) reactance of the interconnector
(c) synchronous reactance of both the alternators
(d) all of the above
Answer: a

96. Electro-mechanical voltage regulators are generally used in
(a) reactors
(b) generators
(c) transformers
(d) all of the above
Answer: b

97. Series capacitors on transmission lines are of little use when the load VAR requirement is
(a) large
(b) small
(b) fluctuating
(d) any of the above
Answer: b

98. The voltage regulation in magnetic amplifier type voltage regulator is effected by
(a) electromagnetic induction
(b) varying the resistance
(c) varying the reactance
(d) variable transformer
Answer: c

99. When a conductor carries more current on the surface as compared to core, it is due to
(a) permeability variation
(b) corona
(c) skin effect
(d) unsymmetrical fault
(e) none of the above
Answer: c

100. The following system is not generally used
(a) 1-phase 3 wire
(b) 1-phase 4 wire
(c) 3-phase 3 wire
(d) 3-phase 4 wire
Answer: b

101. The skin effect of a conductor will reduce as the
(a) resistivity of conductor material increases
(b) permeability of conductor material increases
(c) diameter increases
(d) frequency increases
Answer: a

110. When a live conductor of public electric supply breaks down and touches the earth which of the following will happen ?
(a) Current will flow to earth
(b) Supply voltage will drop
(c) Supply voltage will increase
(d) No current will flow in the conductor
(e) None of the above
Answer: a

TRANSMISSION & DISTRIBUTION Mcqs Interview Questions Pdf ::

SWITCHGEAR & PROTECTION Multiple Choice Questions :-

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
(e) none of the above
Ans: d

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
Ans: d

3. SF6 gas
(a) is yellow in colour
(b) is lighter than air
(c) is nontoxic
(d) has pungent small
(e) none of the above
Ans: c

4. The arcing contacts in a circuit breaker are made of
(a) copper tungsten alloy
(b) porcelain
(c) electrolytic copper
(d) aluminium alloy
Ans: a

5. Which of the following medium is employed for extinction of arc in air circuit breaker ?
(a) Water
(b) Oil
(c) Air
(d) SF6
Ans: c

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
(e) All of the above
Ans: c

7. Fault diverters are basically
(a) fuses
(b) relays
(c) fast switches
(d) circuit breakers
Ans: c

8. A thermal protection switch can protect against
(a) short-circuit
(b) temperature
(c) overload
(d) over voltage
Ans: c

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
Ans: d

10. Thermal circuit breaker has
(a) delayed trip action
(b) instantaneous trip action
(c) both of the above
(d) none of the above
Ans: a

11. Relays can be designed to respond to changes in
(a) resistance, reactance or impedance
(b) voltage and current
(c) light intensity
(d) temperature
(e) all above
Ans: e

12. Overload relays are of…… type.
(a) induction
(b) solid state
(c) thermal
(d) electromagnetic
(e) all above
Ans: e

13. 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
Ans: b

14. Magnetic circuit breaker has ______ trip action.
(a) delayed
(b) instantaneous
(c) both of the above
(d) none of the above
Ans: b

15. 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
Ans: c

16. 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
Ans: d

17. 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
Ans: d

18. 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
Ans: a

19. 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
(e) any of the above
Ans: a

20. 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
(e) none of the above
Ans: c

21. Air blast circuit breaker is used for
(a) over currents
(b) short duty
(c) intermittant duty
(d) repeated duty
Ans: d

22. 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
Ans: d

23. 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
Ans: b

24. Directional relays are based on flow of
(a) power
(b) current
(c) voltage wave
(d) all of the above
Ans: a

25. 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
Ans: c

26. 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)
(e) none of the above
Ans: d

27. 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
Ans: a

28. 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
Ans: c

29. 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
Ans: c

30. The voltage appearing across the contacts after opening of the circuit breaker is called______voltage.
(a) recovery
(b) surge
(c) operating
(d) arc
(e) none of the above
Ans: a

31. 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
Ans: d

32. 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
Ans: c

33. 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
Ans: d

34. 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
Ans: d

35. Shunt capacitance is neglected while considering
(a) short transmission line
(b) medium transmission line
(c) long transmission line
(d) medium and long transmission lines
Ans: a

36. 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
Ans: a

37. 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
(e) none of the above
Ans: a

38. 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
Ans: c

39. H.R.C. fuses provide best protection against
(a) overload
(b) reverse current
(c) open-circuits
(d) short-circuits
Ans: d

40. The ground wire should not be smaller than No ______ copper.
(a) 2
(b) 4
(c) 6
(d) 10
Ans: d

41. The delay fuses are used for the protection of ________ .
(a) motors
(b) power outlet circuits
(c) fluorescent lamps
(d) light circuits
Ans: a

42. 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
(e) None of the above
Ans: a

43. Resistance grounding is used for voltage between
(a) 33kVto66kV
(b) HkVto33kV
(c) 3.3kVandllkV
(d) none of the above
Ans: c

44. 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
(e) none of the above
Ans: c

45. In Railway applications ______ circuit breaker is used.
(a) SFe
(b) bulk oil
(c) minimum oil
(d) air break
Ans:

46. 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
Ans: c

47. 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
Ans: b

48. 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
Ans: d

49. The reflection co-efficient at the open circuited end of a transmission line.
(a) zero
(b) infinity
(c) unity
(d) none of the above
Ans: c

50. 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
(e) none of the above
Ans: c

51. The line insulation is the insulation level of the station equipment.
(a) less than
(b) same as
(c) more than
(d) proportional to
(e) not directly related with
Ans: e

52. 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
Ans: d

53. 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
(e) all of the above
Ans: d

54. Which of the following statements is incorrect?
(a) Station batteries are used to operate relay only
(b) The lightning arresters are basically surge diverters
(c) An impedance relay has maximum fault current when fault occurs near the relay
(d) A high speed relay has an operation of 1 to 2 cycles
Ans: a

55. Discrimination between main and back up protection is provided by the use of relays which are
(a) fact
(b) sensitive
(c) slow
(d) none of the above
Ans: c

56. Induction cup relay is operated due to changes in
(a) current
(b) voltage
(c) impedance
(d) all of the above
Ans: d

57. A.C. network analyser is used to solve problems of
(a) load flow
(b) load flow and short-circuit
(c) load flow and stability
(d) load flow, short-circuit and stability
(e) none of the above
Ans: d

58. Which of the following statements is incorrect ?
(a) Lightning arrestors are used before the switchgear
(b) Shunt reactors are used as compensation reactors
(c) The peak short current is (1.8 xV2) times the A.C. component
(d) The MVA at fault is equal to base MVA divided by per unit equivalent fault reactance
Ans: a

59. Short-circuit currents are due to
(a) single phase to ground faults
(b) phase to phase faults
(c) two phase to ground faults
(d) three phase faults
(e) any of these
Ans: e

60. To reduce short circuit fault currents are used.
(a) reactors
(b) resistors
(c) capacitors
(d) none of the above
Ans: a

61. Bus coupler is very essential in arrangement
(a) single bus
(b) double bus, double breaker
(c) main and transfer bus
(d) all of the above
Ans: c

62. For cost and safety, the outdoor substations are installed for voltages above
(a) 11 kV
(b) 33 kV
(c) 60kV
(d) 110kV
Ans: b

63. The short circuit in any winding of the transformer is the result of
(a) mechanical vibration
(b) insulation failure
(c) loose connection
(d) impulse voltage
Ans: d

64. relays are used for phase faults on long line.
(a) Impedance
(b) Reactance
(c) Either of the above
(d) None of the above
Ans: a

65. For which of the following protection from negative sequence currents is provided ?
(a) Generators
(b) Motors
(c) Transmission line
(d) Transformers
Ans: a

66. relay is preferred for phase fault on short transmission line.
(a) Induction type
(b) Reactance
(c) Impedance
(d) None of the above
Ans: b

67. Distance relays are generally
(a) split-phase relays
(b) reactance relays
(c) impedance relays
(d) none of the above
Ans: d

68. For which of the following ratings of the transformer differential protection is recommended ?
(a) above 30 kVA.
(b) equal to and above 5 MVA
(c) equal to and above 25 MVA
(d) none of the above
Ans: b

69. A _______ is used to measure the stator % winding temperature of the generator.
(a) thermocouple
(b) pyrometer
(c) resistance thermometer
(d) thermometer
Ans: c

70. The under voltage relay can be used for
(a) generators
(b) busbars
(c) transformers
(d) motors
(e) all of the above
Ans: e

71. The relay with inverse time characteristic will operate within
(a) 1.5 sec
(b) 5 to 10 sec
(c) 5 to 20 sec
(d) 20 to 30 sec
(e) none of the above
Ans: b

72. The single phasing relays are used for the protection of
(a) single phase motors only
(b) two phase motors only
(c) two single phase motors running in parallel
(d) three phase motors
Ans: d

73. Which of the following devices will receive voltage surge first travelling on the transmission line ?
(a) Lightning arresters
(b) Relays
(c) Step-down transformer
(d) Switchgear
Ans: a

74. Which of the following parameter can be neglected for a short line ?
(a) Inductance
(b) Capacitance
(c) Resistance
(d) Reactance
Ans: b

75. Series reactors should have
(a) low resistance
(b) high resistance
(c) low impedance
(d) high impedance
Ans: a

76. Which of the following circuit breakers has high reliability and minimum maintenance ?
(a) Air blast circuit breakers
(b) Circuit breaker with SF6 gas
(c) Vacuum circuit breakers
(d) Oil circuit breakers
Ans: b

77. Arc in a circuit breaker is interrupted at
(a) zero current
(b) maximum current
(c) minimum voltage
(d) maximum voltage
Ans: a

78. transmission line has reflection coefficient as one.
(a) Open circuit
(b) Short-circuit
(e) Long
(d) None of the above
Ans: a

79. What will be the reflection co-efficient of the wave of load connected to transmission line if surge impedance of the line is equal to load ?
(a) Zero
(b) Unity
(c) Infinity
(d) None of the above
Ans: a

80. The inverse definite mean time relays are used for over current and earth fault protection of transformer against
(a) heavy loads
(b) internal short-circuits
(c) external short-circuits
(d) all of the above
Ans: b

81. Over voltage protection is recommended for
(a) hydro-electric generators
(b) steam turbine generators
(c) gas turbine generators
(d) all of the above
(e) none of the above
Ans: d

82. Air blast circuit breakers for 400 kV power system are designed to operate in
(a) 100 microsecond
(b) 50 millisecond
(c) 0.5 sec
(d) 0.1 sec
Ans: b

83. Overfluxing protection is recommended for
(a) distribution transformer
(b) generator transformer of the power plant
(c) auto-transformer of the power plant
(d) station transformer of the power plant
Ans: b

84. Series capacitors are used to
(a) compensate for line inductive reactance
(b) compensate for line capacitive reactance
(c) improve line voltage
(d) none of the above
Ans: a

85. Admittance relay is _______ relay.
(a) impedance
(b) directional
(c) non-directional
(d) none of the above
Ans: b

86. The material used for fuse must have
(a) low melting point and high specific resistance
(b) low melting point and -low specific resistance
(c) high melting point and low specific resistance
(d) low melting point and any specific resistance
Ans: a

87. If the fault occurs near the impedance relay, the VII ratio will be
(a) constant for all distances
(b) lower than that of if fault occurs away from the relay
(c) higher than that of if fault occurs away from the relay
(d) none of the above
Ans: b

88. The torque produced in induction type relay (shaded pole structure) is
(a) inversely proportional to the current
(b) inversely proportional to the square of the current
(c) proportional to the current
(d) proportional to square of the current
Ans: b

89. The steady state stability of the power system can be increased by
(a) connecting lines in parallel
(b) connecting lines in series
(e) using machines of high impedance
(d) reducing the excitation of machines
(e) none of the above
Ans: a

90. The inductive interference between power and communication line can be minimized by
(a) transposition of the power line
(b) transposition of the communication line
(c) both (a) and (b)
(d) increasing the distance between the conductors
Ans: c

91. The power loss is an important factor for the design of
(a) transmission line
(b) motor
(c) generator
(d) feeder
Ans: a

92. A fuse is connected
(a) in series with circuit
(b) in parallel with circuit
(c) either in series or in parallel with circuit
(d) none of the above
Ans: a

93. H.R.C. fuse, as compared to a rewirable fuse, has
(a) no ageing effect
(b) high speed of operation
(c) high rupturing capacity
(d) all of the above
Ans: d

94. The fuse rating is expressed in terms of
(a) current
(b) voltage
(c) VAR
(d) kVA
Ans: a

95. The fuse blows off by
(a) burning
(b) arcing
(c) melting
(d) none of the above
Ans: c

96. On which of the following effects of electric current a fuse operates ?
(a) Photoelectric effect
(b) Electrostatic effect
(c) Heating effect
(d) Magnetic effect
Ans: c

97. An isolator is installed
(a) to operate the relay of circuit breaker
(b) as a substitute for circuit breaker
(c) always independent of the position of circuit breaker
(d) generally on both sides of a circuit breaker
Ans: d

98. A fuse in a motor circuit provides protection against
(a) overload
(b) short-circuit and overload
(c) open circuit, short-circuit and overload
(d) none of the above
Ans: b

99. Protection by fuses is generally not used beyond
(a) 20 A
(b) 50 A
(c) 100 A
(d) 200 A
Ans: c

100. A fuse is never inserted in
(a) neutral wire
(b) negative of D.C. circuit
(c) positive of D.C. circuit
(d) phase dine
Ans: a

101. Oil switches are employed for
(a) low currents circuits
(b) low voltages circuits
(c) high voltages and large currents circuits
(d) all circuits
Ans: c

102. A switchgear is device used for
(a) interrupting an electrical circuit
(b) switching an electrical circuit 111.
(c) switching and controlling an electrical circuit
(d) switching, controlling and protecting the electrical circuit and equipment
Ans: d

103. The fuse wire, in D.C. circuits, is inserted in
(a) negative circuit only
(b) positive circuit only
(c) both (a) and (b)
(d) either (a) or (b)
Ans: c

104. By which of the following methods major portion of the heat generated in a H.R.C. fuse is dissipated ?
(a) Radiation
(b) Convection
(c) Conduction
(d) All of the above
Ans: c

105. A short-circuit is identified by
(a) no current flow
(b) heavy current flow
(c) voltage drop
(d) voltage rise
Ans: b

106. The information to the circuit breaker under fault conditions is provided by
(a) relay
(b) rewirable fuse
(c) H.R.C. only
(d) all of the above
Ans: a

107. To limit short-circuit current in a power system are used.
(a) earth wires
(b) isolators
(c) H.R.C. fuses
(d) reactors
Ans: d

109. A balanced 3-phase system consists of
(a) zero sequence currents only
(b) positive sequence currents only
(c) negative and zero sequence currents
(d) zero, negative and positive sequence currents
Ans: b

110. In a single bus-bar system there will be complete shut down when
(a) fault occurs on the bus itself
(b) fault occurs on neutral line
(c) two or more faults occur simultaneously
(d) fault occurs with respect to earthing
Ans: a

SWITCHGEAR & PROTECTION Questions and Answers Pdf Download

CABLES Multiple Choice Questions :-

1. The insulating material for a cable should have
A. low cost
B. high dielectric strength
C. high mechanical strength
D. all of the above
Answer: D

2. Which of the following protects a cable against mechanical injury ?
A. Bedding
B. Sheath
C. Armouring
D. None of the above
Answer: C

3. Which of the following insulation is used in cables ?
A. Varnished cambric
B. Rubber
C. Paper
D. Any of the above
Answer: D

4. Empire tape is
A. varnished cambric
B. vulcanised rubber
C. impregnated paper
D. none of the above
Answer: A

5. The thickness of the layer of insulation on the conductor, in cables, depends upon
A. reactive power
B. power factor
C. voltage
D. current carrying capacity
Answer: C

6. The bedding on a cable consists of
A. hessian cloth
B. jute
C. any of the above
D. none of the above
Answer: C

7. The insulating material for cables should
A. be acid proof
B. be non-inflammable
C. be non-hygroscopic
D. have all above properties
Answer: D

8. In a cable immediately above metallic sheath _____ is provided.
A. earthing connection
B. bedding
C. armouring
D. none of the above
Answer: B

9. The current carrying capacity of cables in D.C. is more thanthat in A.C. mainly due to
A. absence of harmonics
B. non-existence of any stability limit
C. smaller dielectric loss
D. absence of ripples
(e) none of the above
Answer: C

10. In case of three core flexible cable the colour of the neutral is
A. blue
B. black
C. brown
D. none of the above
Answer: A

11. cables are used for 132 kV lines.
A. High tension
B. Super tension
C. Extra high tension
D. Extra super voltage
Answer: D

12. Conduit pipes are normally used to protect _____ cables.
A. unsheathed cables
B. armoured
C. PVC sheathed cables
D. all of the above
Answer: A

13. The minimum dielectric stress in a cable is at
A. armour
B. bedding
C. conductor surface
D. lead sheath
Answer: D

14. In single core cables armouring is not done to
A. avoid excessive sheath losses
B. make it flexible
C. either of the above
D. none of the above
Answer: A

15. Dielectric strength of rubber is around
A. 5 kV/mm
B. 15 kV/mm
C. 30 kV/mm
D. 200 kV/mm
Answer: C

16. Low tension cables are generally used up to
A. 200 V
B. 500 V
C. 700 V
D. 1000 V
Answer: D

17. In a cable, the maximum stress under operating conditions is at
A. insulation layer
B. sheath
C. armour
D. conductor surface
Answer: D

18. High tension cables are generally used up to
A. 11kV
B. 33kV
C. 66 kV
D. 132 kV
Answer: A

19. The surge resistance of cable is
A. 5 ohms
B. 20 ohms
C. 50 ohms
D. 100 ohms
Answer: C

20. PVC stands for
A. polyvinyl chloride
B. post varnish conductor
C. pressed and varnished cloth
D. positive voltage conductor
(e) none of the above
Answer: A

In the cables, the location of fault is usually found out by comparing
A. the resistance of the conductor
B. the inductance of conductors
C. the capacitances of insulated conductors
D. all above parameters
Answer: C

22. In capacitance grading of cables we use a ______ dielectric.
A. composite
B. porous
C. homogeneous
D. hygroscopic
Answer: A

23. Pressure cables are generally not used beyond
A. 11 kV
B. 33 kV
C. 66 kV
D. 132 kV
Answer: C

24. The material for armouring on cable is usually
A. steel tape
B. galvanised steel wire
C. any of the above
D. none of the above
Answer: C

25. Cables, generally used beyond 66 kV are
A. oil filled
B. S.L. type
C. belted
D. armoured
Answer: A

26. The relative permittivity of rubber is
A. between 2 and 3
B. between 5 and 6
C. between 8 and 10
D. between 12 and 14
Answer: A

27. Solid type cables are considered unreliable beyond 66 kV because
A. insulation may melt due to higher temperature
B. skin effect dominates on the conductor
C. of corona loss between conductor and sheath material
D. there is a danger of breakdown of insulation due to the presence of voids
Answer: D

28. If the length of a cable is doubled, its capacitance
A. becomes one-fourth
B. becomes one-half
C. becomes double
D. remains unchanged
Answer: C

29. In cables the charging current
A. lags the voltage by 90°
B. leads the voltage by 90°
C. lags the voltage by 180°
D. leads the voltage by 180°
Answer: B

30. A certain cable has an insulation of relative permittivity 4. If the insulation is replaced by one of relative permittivity 2, the capacitance of the cable will become
A. one half
(6) double
C. four times
D. none of the above
Answer: A

31. If a cable of homogeneous insulation has a maximum stress of 10 kV/mm, then the dielectric strength of insulation should be
A. 5 kV/mm
B. 10 kV/mm
A. 15 kV/mm
D. 30 kV/mm
Answer: B

32. In the cables, sheaths are used to
A. prevent the moisture from entering the cable
B. provide enough strength
(e) provide proper insulation
D. none of the above
Answer: A

33. The intersheaths in the cables are used to
A. minimize the stress
B. avoid the requirement of good insulation
C. provide proper stress distribution
D. none of the above
Answer: C

34. The electrostatic stress in underground cables is
A. same at the conductor and the sheath
B. minimum at the conductor and maximum at the sheath
C. maximum at the conductor and minimum at the sheath
D. zero at the conductor as well as on the sheath
(e) none of the above
Answer: C

35. The breakdown of insulation of the cable can be avoided economically by the use of
A. inter-sheaths
B. insulating materials with different dielectric constants
C. both A. and B.
D. none of the above
Answer: C

36. The insulation of the cable decreases with
A. the increase in length of the insulation
B. the decrease in the length of the insulation
C. either A. or B.
D. none of the above
Answer: A

37. A cable carrying alternating current has
A. hysteresis losses only
B. hysteresis and leakage losses only
C. hysteresis, leakage and copper losses only
D. hysteresis, leakage, copper and friction losses
Answer: B

38. In a cable the voltage stress is maximum at
A. sheath
(6) insulator
(e) surface of the conductor
D. core of the conductor
Answer: D

39. Capacitance grading of cable implies
A. use of dielectrics of different permeabilities
B. grading according to capacitance of cables per km length
C. cables using single dielectric in different concentrations
D. capacitance required to be introduced at different lengths to counter the effect of inductance
(e) none of the above
Answer: A

40. Underground cables are laid at sufficient depth
A. to minimise temperature stresses
B. to avoid being unearthed easily due to removal of soil
C. to minimise the effect of shocks and vibrations due to gassing vehicles, etc.
D. for all of the above reasons
Answer: C

41. The advantage of cables over overhead transmission lines is
A. easy maintenance
B. low cost
C. can be used in congested areas
D. can be used in high voltage circuits
Answer: C

42. The thickness of metallic shielding on cables is usually
A. 0.04 mm
B. 0.2 to 0.4 mm
(e) 3 to 5 mm
D. 40 to 60 mm
Answer: A

43. Cables for 220 kV lines are invariably
A. mica insulated
B. paper insulated
C. compressed oil or compressed gas insulated
D. rubber insulated
(e) none of the above
Answer: C

44. Is a cable is to be designed for use on 1000 kV, which insulation would you prefer ?
A. Polyvinyle chloride
B. Vulcanised rubber
C. Impregnated paper
D. Compressed SFe gas
(e) none of the above
Answer: D

45. If a power cable and a communication cable are to run parallel the minimum distance between the two, to avoid interference, should be
A. 2 cm
B. 10 cm
C. 50 cm
D. 400 cm
Answer: C

46. Copper as conductor for cables is used as
A. annealed
B. hardened and tempered
C. hard drawn
D. alloy with chromium
Answer: A

47. The insulating material should have
A. low permittivity
B. high resistivity
C. high dielectric strength
D. all of the above
Answer: D

48. The advantage of oil filled cables is
A. more perfect impregnation
B. smaller overall size
C. no ionisation, oxidation and formation of voids
D. all of the above
Answer: D

49. The disadvantage with paper as insulating material is
A. it is hygroscopic
(6) it has high capacitance
C. it is an organic material
D. none of the above
Answer: A

50. The breakdown voltage of a cable depends on
A. presence of moisture
B. working temperature
C. time of application of the voltage
D. all of the above
Answer: D

51. It is difficult to maintain oil filled cables.
A. Yes
B. No
Answer: A

51. In capacitance grading a homogeneous dielectric is used.
A. Yes
B. No
Answer: B

52. In congested areas where excavation is expensive and inconvenient ‘draw in system’ of laying of underground cables is often adopted.
A. Yes
B. No
Answer: A

53. Natural rubber is obtained from milky sap of tropical trees.
A. Yes
B. No
Answer: A

54. Rubber is most commonly used insulation in cables.
A. Yes
B. No
Answer: A

59. Polyethylene has very poor dielectric and ageing properties.
A. Yes
B. No
Answer: B

60. The metallic sheath may be made of lead or lead alloy or of aluminium.
A. Yes
B. No
Answer: B

Cables MCQ questions with answers pdf download online exam test

Electrical Engineering Materials Objective Type Questions :-

1. The converse of hardness is known as
(a) malleability
(b) toughness
(c) softness
(d) none of the above
Ans: c

2. On which of the following factors does the resistivity of a material depend ?
(a) Resistance of the conductor
(b) Area of the conductor section
(c) Length of the conductor
(d) All of the above
Ans: d

3. is a negatively charged particle present in an atom.
(a) Proton
(b) Neutron
(c) Electron
(d) None of the above
Ans: c

4. The formula ____ determines the number of electrons that can be accommodated in any level.
(a) 2n2
(6) 4n2
(c) 2n3
(d) 4ns
Ans: a

5. The tiny block formed by the arrangement of a small group of atoms is called the
(a) unit cell
(b) space lattice
(c) either (a) or (b)
(d) none of the above
Ans: a

6. The co-ordination number of a simple cubic structure is
(a) 2
(b) 4
(c) 6
(d) 8
Ans: c

7. The covalent bond is formed by
(a) transfer of electrons between atoms
(b) sharing of electrons between atoms
(e) sharing of variable number of electrons by a variable number of atoms
(d) none of the above
Ans: b

8. A perfect conductor has
(a) zero conductivity
(b) unity conductivity
(c) infinite conductivity
(d) none of the above
Ans: c

9. The metal having the lowest temperature coefficient of resistance is
(a) gold
(b) copper
(c) aluminium
(d) kanthal
Ans: a

10. Commonly used conducting materials are
(a) copper
(b) aluminium
(c) both (a) and (b)
(d) copper and silver
(e) platinum and gold
Ans: c

11. Which of the following materials is preferred for transmitting electrical energy over long distance ?
(a) Copper
(b) Aluminium
(c) Steel reinforced copper
(d) Steel reinforced aluminium
Ans: d

12. The kinetic energy of a bounded electron is
(a) less than that of unbounded electron
(6) greater than that of unbounded electron
(c) equal to that of unbounded electron
(d) infinite
(e) none of the above
Ans: a

13. A highly conductive material must have
(a) highest conductivity
(b) lowest temperature co-efficient
(c) good mechanical strength
(d) good corrosion resistance
(e) easy solderable and drawable quality
(f) all of the above
Ans: f

14. The conductivity of a conductor can be increased by
(a) decreasing its temperature
(b) increasing its temperature
(c) decreasing its vibration
(d) increasing its vibration
Ans: a

15. Superconductivity is observed for
(a) infrared frequencies
(b) d.c. and low frequency
(c) a.c. and high frequency
(d) frequencies having no effect
(e) none of the above
Ans: b

16. The superconductivity is due to
(a) the crystal structure having no atomic vibration at 0°K
(b) all electrons interact in the super-conducting state
(c) the electrons jump into nucleus at 0°K
(d) none of the above
Ans: a

17. The value of critical field below the transition temperature will
(a) increase
(b) decrease
(c) remain unchanged
(d) any of the above
Ans: a

18. In a superconductor the value of critical density depends upon
(a) magnetic field strength
(b) temperature
(c) either (a) or (b)
(d) both (a) and (b)
Ans: d

19. Superconductors are becoming popular for use in
(a) generating very strong magnetic field
(b) manufacture of bubble memories
(c) generating electrostatic field
(d) generating regions free from magnetic field
Ans: a

20. High resistivity materials are used in
(a) precision instruments
(6) heating elements
(c) motor starters
(d) incandescent lamps
(e) all of the above
Ans: e

21. Mercury as an electric contact material is
(a) a liquid
(b) a metal
(c) a metal liquid
(d) a gas
Ans: c

22. An H.R.C. fuse is
(a) a ceramic body having metal and caps
(b) a wire of platinum
(c) a heavy cross-section of copper or aluminium
(d) a ceramic tube having carbon rod inside it
Ans: a

23. Which of the following resistive materials has the lowest temperature co-efficient of resistance ?
(a) Nichrome
(b) Constantan
(c) Kanthal
(d) Molybdenum
Ans: a

24. The coils of D.C. motor starter are wound with wire of
(a) copper
(b) kanthal
(c) manganin
(d) nichrome
Ans: c

25. The conductors have transport phenomena of electrons due to
(a) electric field
(b) magnetic field
(c) electromagnetic field
(d) none of the above
Ans: a

26. The transition temperature of mercury is
(a) 18.0°K
(6) 9.22°K
(c) 4.12°K
(d) 1.14’K
Ans: c

27. By increasing impurity content in the metal alloy the residual resistivity always
(a) decreases
(b) increases
(c) remains constant
(d) becomes temperature independent
Ans: b

28. The structure sensitive property of a super conductor is
(a) critical magnetic field
(b) transition temperature
(c) critical current density
(d) none of the above
Ans: c

29. At transition temperature the value of critical field is
(a) zero
(6) negative real value
(c) positive real value
(d) complex value
Ans: a

30. Which of the following variety of copper has the best conductivity ?
(a) Induction hardened copper
(b) Hard drawn copper
(c) Pure annealed copper
(d) Copper containing traces of silicon
Ans: c

31. Constantan contains
(a) silver and tin
(b) copper and tungsten
(c) tungsten and silver
(d) copper and nickel
Ans: d

32. Which of the following is the poorest conductor of electricity ?
(a) Carbon
(b) Steel
(c) Silver
(d) Aluminium
Ans: a

33 ______ has zero temperature co-efficient of resistance.
(a) Aluminium
(b) Carbon
(c) Porcelain
(d) Manganin
Ans: d

34. Piezoelectric materials serve as a source of _____ .
(a) resonant waves
(b) musical waves
(c) microwaves
(d) ultrasonic waves
Ans: d

35. In thermocouples which of the following pairs is commonly used ?
(a) Copper-constantan
(b) Aluminium-tin
(c) Silver-German silver
(d) Iron-steel
Ans: a

36. is viscoelastic.
(a) Cast-iron
(6) Graphite
(c) Rubber
(d) Glass
Ans: c

37. Carbon electrodes are not used in
(a) GLS lamps
(b) electric arc furnace
(c) dry cells
(d) cinema projectors
Ans: a

38. Solder is an alloy of
(a) copper and aluminium
(b) tin and lead
(c) nickel, copper and zinc
(d) silver, copper and lead
Ans: b

39 ______ is most commonly used for making magnetic recording tape
(a) Silver nitrate
(b) Ferric oxide
(c) Small particles of iron
(d) Silicon-iron
Ans: b

40. Overhead telephone wires are made of
(a) aluminium
(b) steel
(c) ACSR conductors
(d) copper
Ans: b

41. ______ is an example of piezoelectric material.
(a) Glass
(b) Quartz
(c) Corrundum
(d) Neoprene
Ans: b

42. _____ is the main constituent of glass
(a) Fe203
(b) Si02
(c) AI2O3
(d) B2O3
Ans: b

43. A good electric contact material should have all of the following properties except
(a) high resistivity
(b) high resistance to corrosion
(c) good thermal conductivity
(d) high melting point
Ans: a

44. Most of the common metals have _____ structure.
(a) linear
(b) hexagonal
(c) orthorhombic
(d) cubic
Ans: d

45. Which of the following affect greatly the resistivity of electrical conductors ?
(a) Composition
(b) Pressure
(c) Size
(d) Temperature
Ans: a

46. Thermonic emission occurs in
(a) vacuum tubes
(b) copper conductors
(c) ferrite cores
(d) transistors
Ans: a

47. _____ is a hard solder.
(a) Tin-lead
(6) Tin-silver-lead
(c) Copper-zinc
(d) None of the above
Ans: c

48. Addition of 0.3 to 4.5% silicon to iron _____ the electrical resistivity of iron.
(a) increases
(b) decreases
(c) does not change
Ans: a

49. Super conductivity can be destroyed by
(a) adding impurities
(b) reducing temperatures
(c) application of magnetic field
(d) any of the above
Ans: c

50. Non-linear resistors
(a) produce harmonic distortion
(b) follows Ohm’s law at low temperatures only
(c) result in non-uniform heating
(d) none of the above
Ans: a

51. A carbon resistor contains
(a) carbon crystals
(b) solid carbon granules
(c) pulverized coal
(d) finely divided carbon black.
Ans: d

52. Which of the following materials does not have covalent bonds ?
(a) Organic polymers
(b) Silicon
(c) Metals
Ans: c

53. In graphite, bonding is
(a) covalent
(b) metallic
(c) Vander Waals
(d) Vander Waals and covalent
Ans: d

54. Total number of crystal systems is
(a) 2
(b) 4
(c) 7
(d) 12
Ans: c

55. The number of atoms per unit cell in B.C.C. structure is
(a) 1
(b) 2
(c) 4
(d) 8
Ans: b

56. The conductivity of a metal is determined by
(a) the electronic concentration and the mobility of the free electrons
(6) the number of valence electrons per atom
(c) either (a) or (b)
(d) none of the above
Ans: a

57. The resistivity of a metal is a function of temperature because
(a) the amplitude of vibration of the atoms varies with temperature
(b) the electron density varies with temperature
(c) the electron gas density varies with temperature
Ans: a

58. In a crystal, an atom vibrates at a frequency determined by
(a) the heat content of the crystal
(b) the temperature of the crystal
(c) the stiffness of the bonds it makes with neighbors
Ans: c

59. Due to which of the following reasons aluminium does not corrode in atmosphere ?
(a) Aluminium is a noble metal
(b) Atmospheric oxygen can only diffuse very slowly through the oxide layer which is formed on the surface of aluminium
(c) No reaction with oxygen occurs ft Any of the above
Ans: b

60. The impurity atoms is semiconductors
(a) inject more charge carriers
(6) reduce the energy gap
(c) increase the kinetic energy of valence electrons
(d) all of the above
Ans: b

61. Which of the following material is not a semiconductor ?
(a) Silica
(b) Germanium
(c) Selenium
(d) Gallium-arsenide
Ans: a

62. Carbon resistors are used extensively because they are
(a) easy to make
(b) compact
(c) inexpensive
(d) all of the above reasons
Ans: d

63. Carbon rods are used in wet and dry cells because
(a) carbon rod serves as conductor
(b) carbon can resist the attack of battery acid
(c) both (a) and (b)
(d) either (a) or (b)
Ans: c

64. Due to which of the following factors the brush wear rate is altered ?
(a) Speed of the machine
(b) Contact pressure
(c) Surface conditions of brush and commutator
(d) Excessive sparking
(e) All of the above
Ans: e

65. Which of the following are non-conductors of electricity?
(a) Non-metal solids except carbon
(b) Air and most other gases
(c) Pure water and liquids in general except mercury
(d) All of the above
Ans: d

66. Carbon bearings are used under which of the following conditions ?
(a) Where lubrication is difficult or im-possible
(b) Where corrosive chemical action exists
(c) Where high temperature exists
(d) All of the above
Ans: d

67. Which of the following high resistance materials has the highest operating temperature ?
(a) Kanthal
(b) Manganin
(c) Nichrome
(d) Eureka
Ans: a

68. Steel wire is used as
(a) overhead telephone wire
(b) earth wire
(c) core wire of ACSR
(d) all of the above
Ans: d

69. Low resistivity materials are used in
(a) transformer, motor and generator windings
(b) transmission and distribution lines
(c) house wiring
(d) all above applications
Ans: d

70. Platinum is used in
(a) electrical contacts
(b) thermocouple
(c) heating element in high temperature furnace
(d) grids of special purpose vacuum tubes
(e) all of the above
Ans: e

71. Which of the following is an advantage of stranded conductor over equivalent single conductor ?
(a) Less liability to kink
(b) Greater flexibility
(c) Less liability to break
(d) All of the above
Ans: d

72. Due to which of the following reasons copper and aluminium are not used for heating elements ?
(a) Both have great tendency for oxidation
(b) Both have low melting point
(c) Very large length of wires will be required
(d) All of the above
Ans: d

73. Copper, even though costly, finds use in the windings of electrical machines because
(a) copper points offer low contact resistance
(b) copper can be easily soldered and welded
(e) copper windings are less bulky and the machines become compact
(d) all of the above
Ans: d

74. Which of the following materials is used for making coils of standard resistances ?
(a) Copper
(b) Nichrome
(c) Platinum
(d) Manganin
Ans: d

75. Substances whose specific resistance abruptly decreases at very low temperature are called
(a) insulators
(b) conductors
(c) semiconductors
(d) superconductors
Ans: d

76. Which of the following materials is the best conductor of electricity ?
(a) Tungsten
(b) Aluminium
(c) Copper
(d) Carbon
Ans: c

77. is the property of absorbing moisture from atmosphere.
(a) Solubility
(b) Viscosity
(c) Porosity
(d) Hygroscopicity
Ans: d

78. Thermocouples are mainly used for the measurement of
(a) temperature
(b) resistance
(c) eddy currents
(d) coupling co-efficient
Ans: a

79. Due to which of the following fact, in India, aluminium is replacing copper ?
(a) Aluminium is more ductile and malleable than copper
(6) Aluminium is available in plenty, cheaper and lighter than copper
(c) Aluminium has lower resistivity than that of copper
(d) Aluminium has less temperature co-efficient than copper
Ans: b

80. The conduction of electricity, in semiconductors, takes place due to movement of
(a) positive ions only
(b) negative ions only
(c) positive and negative ions
(d) electrons and holes
Ans: d

81. Which of the following is a semiconductor material ?
(a) Phosphorous
(b) Rubber
(c) Silicon
(d) Aluminium
Ans: c

82. Selenium is _____ semiconductor.
(a) extrnisic
(b) intmisic
(c) N-type
(d) P-type
Ans: b

83. ________ has the best damping properties.
(a) Diamond
(b) High speed steel
(c) Mild steel
(d) Cast iron
Ans: d

84. The photo-electric effect occurs only when the incident light has more than a certain critical
(a) intensity
(b) speed
(c) frequency
(d) wave length
Ans: c

85. If the resistance of a conductor does not vary in accordance with Ohm’s law it is known as
(a) non-linear conductor
(b) reverse conductor
(c) bad-conductor
(d) non-conductor
Ans: a

86. Spark plug makes use of which of the following materials for insulation ?
(a) Porcelain
(b) Slate
(c) Asbestos
(d) Glass
Ans: a

87. The forbidden gap in an insulator is
(a) large
(b) small
(c) nil
(d) any of the above
Ans: a

88. Which of the following factors affect resistivity of metals ?
(a) Age hardening
(b) Alloying
(c) Temperature
(d) Cold work
(e) All of the above
Ans: e

89. Effect of moisture on the insulating materials is to
(a) decrease dielectric constant
(b) decrease dielectric strength
(c) decrease insulation resistance
(d) increase dielectric loss
(e) all of the above
Ans: e

90. Surface resistance of an insulating material is reduced due to the
(a) smoky and dirty atmosphere
(b) humidity in the atmosphere
(c) both (a) and (b)
(d) neither (a) nor (b)
Ans: c

91. Superconducting metal in super conducting state has relative permeability of
(a) zero
(b) one
(c) negative
(d) more than one
Ans: a

92. In conductors conduction of electricity takes place due to movement of
(a) electrons only
(b) positive ions only
(c) negative ions only
(d) positive and negative ions
(e) none of the above
Ans: a

93. The carbon percentage is least in
(a) low carbon steel
(b) wrought iron
(c) cast iron
(d) malleable iron
Ans: b

94. For a particular material the Hall coefficient was found to be zero. The material is
(a) insulator
(6) metal
(c) intrinsic semiconductor
(d) none of the above
Ans: b

95. The conductivity of an extrinsic semiconductor with temperature
(a) decreases
(b) increases
(c) remains constant
Ans: c

96. The current due to electron flow in conduction band is the hole current in valence band.
(a) equal to
(b) less than
(c) greater than
(d) any of the above
Ans: c

97. For a hole which of the following statements is incorrect ?
(a) Holes can exist in certain semiconductors only
(b) Holes can exist in any material including conductors
(c) Holes may constitute an electric current
(d) Holes can be considered as a net positive charge
Ans: b

98. is an element used in semiconductors whose atoms have three valence electrons.
(a) An acceptor
(b) A donor
(c) Germanium
(d) Silicon
Ans: a

99. The minority carrier concentration is largely a function of
(a) forward biasing voltage
(b) reverse biasing voltage
(c) temperature
(d) the amount of doping
Ans: c

100. For germanium the forbidden energy gap is
(a) 0.15 eV
(b) 0.25 eV
(C) 0.5eV
(d) 0.7eV
Ans: d

Measurement & Instrumentation Objective Questions :-

1. The use of _____ instruments is merely confined within laboratories as standardizing instruments.
A. absolute
B. indicating
C. recording
D. integrating
E. none of the above
Answer: A

2. Which of the following instruments indicate the instantaneous value of the electrical quantity being measured at the time at which it is being measured ?
A. Absolute instruments
B. Indicating instruments
C. Recording instruments
D. Integrating instruments
Answer: B

3. _____ instruments are those which measure the total quantity of electricity delivered in a particular time.
A. Absolute
B. Indicating
C. Recording
D. Integrating
Answer: D

4. Which of the following are integrating instruments ?
A. Ammeters
B. Voltmeters
C. Wattmeters
D. Ampere-hour and watt-hour meters
Answer: D

5. Resistances can be measured with the help of
A. wattmeters
B. voltmeters
C. ammeters
D. ohmmeters and resistance bridges
E. all of the above
Answer: D

6 According to application, instruments are classified as
A. switch board
B. portable
C. both A. and B.
D. moving coil
E. moving iron
F. both D and E
Answer: C

7. Which of the following essential features is possessed by an indicating instrument ?
A. Deflecting device
B. Controlling device
C. Damping device
D. All of the above
Answer: D

8. A _____ device prevents the oscillation of the moving system and enables the latter to reach its final position quickly
A. deflecting
B. controlling
C. damping
D. any of the above
Answer: C

9. The spring material used in a spring control device should have the following property.
A. Should be non-magnetic
B. Most be of low temperature co-efficient
C. Should have low specific resistance
D. Should not be subjected to fatigue
E. All of the above
Answer: E

10. Which of the following properties a damping oil must possess ?
A. Must be a good insulator
B. Should be non-evaporating
C. Should not have corrosive action upon the metal of the vane
D. The viscosity of the oil should not change with the temperature
E. All of the above
Answer: E

11. A moving-coil permanent-magnet instrument can be used as _____ by using a low resistance shunt.
A. ammeter
B. voltmeter
C. flux-meter
D. ballistic galvanometer
Answer: A

12. A moving-coil permanent-magnet instrument can be used as flux-meter
A. by using a low resistance shunt
B. by using a high series resistance
C. by eliminating the control springs
D. by making control springs of large moment of inertia
Answer: C

13. Which of the following devices may be used for extending the range of instruments ?
A. Shunts
B. Multipliers
C. Current transformers
D. Potential transformers
E. All of the above
Answer: E

14. An induction meter can handle current up to
A. 10 A
B. 30 A
C. 60 A
D. 100 A
Answer: D

15. For handling greater currents induction wattmeters are used in conjunction with
A. potential transformers
B. current transformers
C. power transformers
D. either of the above
(e) none of the above
Answer: B

16. Induction type single phase energy meters measure electric energy in
A. kW
B. Wh
C. kWh
D. VAR
E. None of the above
Answer: C

17. Most common form of A.C. meters met with in every day domestic and industrial installations are
A. mercury motor meters
B. commutator motor meters
C. induction type single phase energy meters
D. all of the above
Answer: C

18. Which of the following meters are not used on D.C. circuits
A. Mercury motor meters
B. Commutator motor meters
C. Induction meters
D. None of the above
Answer: C

19. Which of the following is an essential part of a motor meter ?
A. An operating torque system
B. A braking device
C. Revolution registering device
D. All of the above
Answer: D

20. A potentiometer may be used for
A. measurement of resistance
B. measurement of current
C. calibration of ammeter
D. calibration of voltmeter
E. all of the above
Answer: E

21 is an instrument which measures the insulation resistance of an electric circuit relative to earth and one another,
A. Tangent galvanometer
B. Meggar
C. Current transformer
D. None of the above
Answer: B

22. The household energy meter is
A. an indicating instrument
B. a recording instrument
C. an integrating instrument
D. none of the above
Answer: C

23. The pointer of an indicating instrument should be
A. very light
B. very heavy
C. either A or B
D. neither A nor B
Answer: A

24. The chemical effect of current is used in
A. D.C. ammeter hour meter
B. D.C. ammeter
C. D.C. energy meter
D. none of the above
Answer: A

25. In majority of instruments damping is provided by
A. fluid friction
B. spring
C. eddy currents
D. all of the above
Answer: C

26. An ammeter is a
A. secondary instrument
B. absolute instrument
C. recording instrument
D. integrating instrument
Answer: A

27. In a portable instrument, the controlling torque is provided by
A. spring
B. gravity
C. eddy currents
D. all of the above
Answer: A

28. The disc of an instrument using eddy current damping should be of
A. conducting and magnetic material
B. non-conducting and magnetic material
C. conducting and non-magnetic material
D. none of the above
Answer: C

29. The switch board instruments
A. should be mounted in vertical position
B. should be mounted in horizontal position
C. either A or B
D. neither A nor B
Answer: A

30. The function of shunt in an ammeter is to
A. by pass the current
B. increase the sensitivity of the ammeter
C. increase the resistance of ammeter
D. none of the above
Answer: A

31. The multiplier and the meter coil in a voltmeter are in
A. series
B. parallel
C. series-parallel
D. none of the above
Answer: A

32. A moving iron instrument can be used for
A. D.C. only
B. A.C. only
C. both D.C. and A.C.
Answer: C

33. The scale of a rectifier instrument is
A. linear
B. non-linear
C. either A or B
D. neither A nor B
Answer: A

34. For measuring current at high frequency we should use
A. moving iron instrument
B. electrostatic instrument
C. thermocouple instrument
D. none of the above
Answer: C

35. The resistance in the circuit of the moving coil of a dynamometer wattmeter should be
A. almost zero
B. low
C. high
D. none of the above
Answer: C

36. A dynamometer wattmeter can be used for
A. both D.C. and A.C.
B. D.C. only
C. A.C. only
D. any of the above
Answer: A

37. An induction wattmeter can be used for
A. both D.C. and A.C.
B. D.C. only
C. A.C. only
D. any of the above
Answer: B

38. The pressure coil of a wattmeter should be connected on the supply side of the current coil when
A. load impedance is high
B. load impedance is low
C. supply voltage is low
D. none of the above
Answer: A

39. In a low power factor wattmeter the pressure coil is connected
A. to the supply side of the current coil
B. to the load side of the current coil
C. in any of the two meters at connection
D. none of the above
Answer: B

40. In a low power factor wattmeter the compensating coil is connected
A. in series with current coil
B. in parallel with current coil
C. in series with pressure coil
D. in parallel with pressure coil
Answer: C

41. In a 3-phase power measurement by two wattmeter method, both the watt meters had identical readings. The power factor of the load was
A. unity
B. 0.8 lagging
C. 0.8 leading
D. zero
Answer: A

42. In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The power factor of the load must be
A. unity
B. 0.5
C. 0.3
D. zero
Answer: B

43. The adjustment of position of shading bands, in an energy meter is done to provide
A. friction compensation
B. creep compensation
C. braking torque
D. none of the above
Answer: A

44. An ohmmeter is a
A. moving iron instrument
B. moving coil instrument
C. dynamometer instrument
D. none of the above
Answer: B

45. When a capacitor was connected to the terminal of ohmmeter, the pointer indicated a low resistance initially and then slowly came to infinity position. This shows that capacitor is
A. short-circuited
B. all right
C. faulty
Answer: B

46. For measuring a very high resistance we should use
A. Kelvin’s double bridge
B. Wheat stone bridge
C. Meggar
D. None of the above
Answer: C

47. The electrical power to a meggar is provided by
A. battery
B. permanent magnet D.C. generator
C. AC. generator
D. any of the above
Answer: B

48. In a meggar controlling torque is provided by
A. spring
B. gravity
C. coil
D. eddy current
Answer: C

49. The operating voltage of a meggar is about
A. 6 V
B. 12 V
C. 40 V
D. 100 V
Answer: D

50. Murray loop test can be used for location of
A. ground fault on a cable
B. short circuit fault on a cable
C. both the ground fault and the short-circuit fault
D. none of the above
Answer: C

51. Which of the following devices should be used for accurate measurement of low D.C. voltage ?
A. Small range moving coil voltmeter
B. D.C. potentiometer
C. Small range thermocouple voltmeter
D. None of the above
Answer: B

52. It is required to measure the true open circuit e.m.f. of a battery. The best device is
A. D.C. voltmeter
B. Ammeter and a known resistance
C. D.C. potentiometer
D. None of the above
Answer: C

53. A voltage of about 200 V can be measured
A. directly by a D.C. potentiometer
B. a D.C. potentiometer in conjunction with a volt ratio box
C. a D.C. potentiometer in conjunction with a known resistance
D. none of the above
Answer: B

54. A direct current can be measured by
A. a D.C. potentiometer directly
B. a D.C. potentiometer in conjunction with a standard resistance
C. a D.C. potentiometer in conjunction with a volt ratio box
D. none of the above
Answer: B

55. To measure a resistance with the help of a potentiometer it is
A. necessary to standardise the potentiometer
B. not necessary to standardise the potentiometer
C. necessary to use a volt ratio box in conjunction with the potentiometer
D. none of the above
Answer: B

56. A phase shifting transformer is used in conjunction with
A. D.C. potentiometer
B. Drysdale potentiometer
C. A.C. co-ordinate potentiometer
D. Crompton potentiometer
Answer: B

57. Basically a potentiometer is a device for
A. comparing two voltages
B. measuring a current
C. comparing two currents
D. measuring a voltage
E. none of the above
Answer: A

58. In order to achieve high accuracy, the slide wire of a potentiometer should be
A. as long as possible
B. as short as possible
C. neither too small not too large
D. very thick
Answer: A

59. To measure an A. C. voltage by using an A.C. potentiometer, it is desirable that the supply for the potentiometer in taken
A. from a source which is not the same as the unknown voltage
B. from a battery
C. from the same source as the unknown voltage
D. any of the above
Answer: C

60. The stator of phase shifting transformer for use in conjunction with an A.C. potentiometer usually has a
A. single-phase winding
B. two-phase winding
C. three-phase winding
D. any of the above
Answer: B

61. In an AC. co-ordinate potentiometer, the currents in the phase and quadrature potentiometer are adjusted to be
A. out of phase by 90°
(6) out of phase by 60°
C. out of phase by 30°
D. out of phase by 0°
E. out of phase by 180°
Answer: A

62. A universal RLC bridge uses
A. Maxwell bridge configuration for measurement of inductance and De Santas bridge for measurement of capacitance
B. Maxwell Wein bridge for measurement of inductance and modified De Santy’s bridge for measurement of capacitance
C. Maxwell Wein bridge for measurement of inductance and Wein bridge for measurement of capacitance
D. Any of the above.
Answer: B

63. For measurements on high voltage capacitors, the suitable bridge is
A. Wein bridge
B. Modified De Santy’s bridge
C. Schering bridge
D. Any of the above
E. None of the above
Answer: C

64. In an Anderson bridge, the unknown inductance is measured in terms of
A. known inductance and resistance
B. known capacitance and resistance
C. known resistance
D. known inductance
Answer: B

65. Wagner earthing device is used to eliminate errors due to
A. electrostatic coupling
B. electromagnetic coupling
C. both A. and B.
D. none of the above
Answer: A

66. For measurement of mutual inductance we can use
A. Anderson bridge
B. Maxwell’s bridge
C. Heaviside bridge
D. Any of the above
Answer: C

67. For measurement of inductance having high value, we should use
A. Maxwell’s bridge
B. Maxwell Wein bridge
C. Hay’s bridge
D. Any of the above
Answer: C

68. If the current in a capacitor leads the voltage by 80°, the loss angle of the capacitor is
A. 10°
B. 80°
C. 120°
D. 170°
Answer: A

69. In a Schering bridge the potential of the detector above earth potential is
A. a few volts only
B. 1 kV
C. 5 kV
D. 10 kV
Answer: A

70. To avoid the effect of stray magnetic field in A.C. bridges we can use
A. magnetic screening
B. Wagner earthing device
C. wave filters
D. any of the above
Answer: A

71. If an inductance is connected in one arm of bridge and resistances in the remaining three arms
A. the bridge can always be balanced
B. the bridge cannot be balanced
C. the bridge can be balanced if the resistances have some specific values
Answer: B

72. A power factor meter has
A. one current circuit and two pressure circuits
B. one current circuit and one pressure circuit
C. two current circuits and one pres¬sure circuit
D. none of the above
Answer: A

73. The two pressure coils of a single phase power factor meter have
A. the same dimensions and the same number of turns
B. the same dimension but different number of turns
C. the same number of turns but different dimensions
D. none of the above
Answer: A

74. In a single phase power factor meter the phase difference between the currents in the two pressure coils is
A. exactly 0°
B. approximately 0°
C. exactly 90°
D. approximately 90°
Answer: C

75. In a dynamo meter 3-phase power factor meter, the planes of the two moving coils are at
A. 0°
B. 60°
C. 90°
D. 120°
Answer: D

76. In a vibrating reed frequency meter the natural frequencies of two adjacent reeds have a difference of
A. 0.1 Hz
B. 0.25 Hz
C. 0.5 Hz
D. 1.5 Hz
Answer: C

77. In a Weston frequency meter, the magnetic axes of the two fixed coils are
A. parallel
B. perpendicular
C. inclined at 60°
D. inclined at 120°
Answer: B

78. A Weston frequency meter is
A. moving coil instrument
B. moving iron instrument
C. dynamo meter instrument
D. none of the above
Answer: B

79. A Weston synchronoscope is a
A. moving coil instrument
B. moving iron instrument
C. dynamometer instrument
D. none of the above
Answer: C

80. In a Weston synchronoscope, the fixed coils are connected across
A. bus-bars
B. incoming alternator
C. a lamp
D. none of the above
Answer: B

81. In Weston synchronoscope the moving coil is connected across
A. bus-bars
B. incoming alternator
C. fixed coils
D. any of the above
Answer: A

82. The power factor of a single phase load can be calculated if the instruments available are
A. one voltmeter and one ammeter
B. one voltmeter, one ammeter and one wattmeter
C. one voltmeter, one ammeter and one energy meter
D. any of the above
Answer: B

83. The desirable static characteristics of a measuring system are
A. accuracy and reproducibility
B. accuracy, sensitivity and reproducibility
C. drift and dead zone
D. static error
Answer: B

84. The ratio of maximum displacement deviation to full scale deviation of the instrument is called
A. static sensitivity
B. dynamic deviation
C. linearity
D. precision or accuracy
Answer: C

85. Systematic errors are
A. instrumental errors
B. environmental errors
C. observational errors
D. all of the above
Answer: D

86. Standard resistor is made from
A. platinum
B. maganin
C. silver
D. nichrome
Answer: B

87. Commonly used standard capacitor is
A. spherical type
B. concentric cylindrical type
C. electrostatic type
D. multilayer parallel plate type
Answer: B

88. Operating torques in analogue instruments are
A. deflecting and control
B. deflecting and damping
C. deflecting, control and damping
D. vibration and balancing
Answer: C

89. Commonly used instruments in power system measurement are
A. induction
B. moving coil or iron
C. rectifier
D. electrostatic
Answer: A

90. Damping of the Ballistic galvanometer is made small to
A. get first deflection large
B. make the system oscillatory
C. make the system critically damped
D. get minimum overshoot
Answer: A

91. If an instrument has cramped scale for larger values, then it follows
A. square law
B. logarithmic law
C. uniform law
D. none of the above
Answer: B

92. Volt box is a component to
A. extend voltage range
(6) measure voltage
C. compare voltage in a box
D. none of the above
Answer: A

93. E.m.f. of a Weston cell is accurately measured by
A. electrostatic voltmeter
B. hot wire voltmeter
C. isothermal voltmeter
D. electrodynamic voltmeter
Answer: A

94. The gravity controlled instrument has crowded scale because current is proportional to
A. balancing weight
B. deflection angle
C. sine of deflection angle
Answer: C

95. A sensitive galvanometer produces large deflection for a
A. small value of current
B. large value of current
C. large value of power
D. large value of voltage
(e) none of the above
Answer: A

96. A multirangq instrument has
A. multiple shunt or series resistances inside the meter
B. multicoii arrangement
C. variable turns of coil
D. multi range meters inside the measurement system
E. any of the above
Answer: A

97. The rectifier instrument is not free from
A. temperature error
B. wave shape error
C. frequency error
D. all of the above
Answer: C

98. Alternating current is measured by
A. induction ammeter
B. permanent magnet type ammeter
C. electrostatic ammeter
D. moving iron repulsion type voltmeter
Answer: A

99. Most sensitive galvanometer is
A. elastic galvanometer
B. vibration galvanometer
C. Duddlb galvanometer
D. spot ballistic galvanometer
Answer: D

100. Instrument transformers are
A. potential transformers
B. current transformers
C. both A. and B.
D. power transformers
Answer: C

101. An instrument transformer is used to extend the range of
A. induction instrument
B. electrostatic instrument
C. moving coil instrument
D. any of the above
Answer: A

102. Wattmeter cannot be designed on the principle of
A. electrostatic instrument
B. thermocouple instrument
C. moving iron instrument
D. electrodynamic instrument
Answer: C

103. In an energy meter braking torque is produced to
A. safe guard it against creep
B. brake the instrument
C. bring energy meter to stand still
D. maintain steady speed and equal to driving torque
Answer: D

104. Various adjustments in an energy meter include
A. light load or friction
B. lag and creep
C. overload and voltage compensation
D. temperature compensation
(e) all of the above
Answer: E

105. The power of a n-phase circuit can be measured by using a minimum of
A. (n – 1) wattmeter elements
B. n wattmeter elements
C. (n + 1) wattmeter elements
D. 2n wattmeter elements
Answer: A

106. Two holes in the disc of energy meter are drilled at the opposite sides of the spindle to
A. improve its ventilation
B. eliminate creeping at no load
C. increase its deflecting torque
D. increase its braking torque
Answer: B

107. Which of the following is measured by using a vector voltmeter ?
A. Amplifier gain and phase shift
B. Filler transfer functions
C. Complex insersion loss
D. All of the above
Answer: D

108. The principle on which vector voltmeter is based is
A. that it works on the principle of complex variation
B. that it measures the response of linear ramp voltage
C. same as digital meter
D. that it measures the amplitude of a single at two points and at the same time measures their phase difference
Answer: D

110. To measure radio frequency, the suitable frequency meter is
A. Weston frequency meter
B. reed vibrator frequency meter
C. heterodoxy frequency meter
D. electrical resonance frequency meter
Answer: C

Measurement & Instrumentation Multiple Choice Questions with Answers pdf Download Online test Quiz