Electrical Engineering PPSC Important MCQs from Past Papers

1. : The insulators used in transmission lines are made of: — From PPSC Electrical Engineer Exam, 2020

(A) Copper

(B) Porcelain

(C) Aluminum

(D) Steel

2. : The power loss in a transmission line is proportional to: — From WAPDA Power Division Test, 2018

(A) I

(B) I²

(C) V

(D) V²

3. : Transmission efficiency increases with: — From PPSC Sub Engineer (Electrical) Exam, 2022

(A) Low voltage

(B) High voltage

(C) High current

(D) Low power factor

4. : In hydroelectric power stations, the turbine is driven by: — From WAPDA Hydel Power Wing Exam, 2021

(A) Steam

(B) Gas

(C) Water

(D) Wind

5. : The domestic voltage supply in Pakistan is: — From PPSC Technical Post Test, 2019

(A) 110 V

(B) 220 V

(C) 230 V

(D) 240 V

6. : The function of a lightning arrester is to: — From WAPDA Electrical Transmission Exam, 2019

(A) Prevent short circuits

(B) Protect equipment from lightning surges

(C) Maintain voltage regulation

(D) Interrupt current flow

7. : Ferranti effect occurs in: — From PPSC Power System Engineer Test, 2021

(A) Short transmission lines under full load

(B) Long transmission lines under light load

(C) DC lines only

(D) Low-voltage cables

8. : The advantage of three-phase system over single-phase is: — From WAPDA Electrical Cadre Test, 2020

(A) High voltage drop

(B) Uneven load

(C) Constant power and smaller conductor size

(D) Reduced power factor

9. : The frequency of alternator output depends on: — From PPSC Electrical Sub Engineer Paper, 2019

(A) Number of poles and speed of rotation

(B) Load on alternator

(C) Magnetic field strength

(D) Excitation voltage

10. : Reactive power in AC systems is measured in: — From WAPDA Grid Operation Exam, 2018

(A) Watts

(B) Joules

(C) Volt-Amperes

(D) Volt-Amperes Reactive (VAR)

11. : The main cause of corona discharge is: — From PPSC Junior Engineer (Electrical) Exam, 2021

(A) Low current

(B) High voltage and non-uniform field

(C) Low frequency

(D) High current

12. : Transmission lines are transposed to: — From WAPDA Transmission Wing Test, 2019

(A) Reduce corona

(B) Reduce voltage drop

(C) Minimize interference and unbalance

(D) Increase capacitance

13. : Which component steps up the voltage in a power station? — From PPSC Power Distribution Exam, 2020

(A) Transformer

(B) Inductor

(C) Alternator

(D) Motor

14. : The load factor of a power plant is the ratio of: — From WAPDA Generation Department Exam, 2018

(A) Maximum demand to average load

(B) Average load to maximum demand

(C) Installed capacity to actual load

(D) None of these

15. : The synchronous speed of a 6-pole alternator running at 50 Hz is: — From FPSC Electrical Engineer Test, 2019

(A) 3000 rpm

(B) 1500 rpm

(C) 1000 rpm

(D) 750 rpm

16. : The material commonly used for overhead transmission line conductors is: — From PPSC Sub Engineer (Electrical) Paper, 2021

(A) Copper

(B) Aluminum

(C) Iron

(D) Steel only

17. : The main disadvantage of DC transmission is: — From WAPDA Technical Post Exam, 2019

(A) High line losses

(B) High insulation cost

(C) No transformers

(D) All of these

18. : The main advantage of HVDC transmission is: — From PPSC Electrical Engineer Exam, 2022

(A) Higher line losses

(B) No charging current and lower cost

(C) High corona losses

(D) Complex switching

19. : In transmission systems, skin effect is more pronounced at: — From WAPDA Electrical Division Test, 2020

(A) Low frequencies

(B) High frequencies

(C) DC currents

(D) Constant current circuits

20. : The primary function of a circuit breaker is to: — From PPSC Assistant Engineer (Electrical) Paper, 2021

(A) Measure voltage

(B) Open or close a circuit under fault conditions

(C) Step up the voltage

(D) Control frequency

21. : The main function of a protective relay is to: — From PPSC Electrical Sub Engineer Exam, 2021

(A) Detect faults and send trip signal to circuit breaker

(B) Regulate voltage

(C) Control power factor

(D) Indicate load condition

22. : A fuse is used for: — From WAPDA Technical Services Test, 2019

(A) Voltage regulation

(B) Overcurrent protection

(C) Frequency control

(D) Power factor correction

23. : The operating time of a fuse depends on: — From FPSC Assistant Engineer (Electrical) Exam, 2020

(A) Circuit voltage

(B) Type of load

(C) Magnitude of current

(D) Length of wire

24. : The main function of a circuit breaker is to: — From WAPDA Electrical Cadre Test, 2018

(A) Indicate current

(B) Make or break circuit under fault condition

(C) Supply backup power

(D) Step up voltage

25. : Which type of relay operates when both magnitude and direction of current are to be considered? — From PPSC Power Protection Exam, 2021

(A) Overcurrent relay

(B) Differential relay

(C) Directional relay

(D) Distance relay

26. : The Buchholz relay is used for protection of: — From WAPDA Generation Division Exam, 2019

(A) Synchronous motors

(B) Transmission lines

(C) Power transformers

(D) Alternators

27. : The minimum operating voltage of a relay is known as: — From PPSC Electrical Engineer Paper, 2020

(A) Pick-up voltage

(B) Drop-out voltage

(C) Holding voltage

(D) Reset voltage

28. : The function of an isolator is to: — From WAPDA Grid Station Test, 2020

(A) Interrupt short-circuit current

(B) Disconnect circuit under no load

(C) Protect against lightning

(D) Control frequency

29. : The breaking capacity of a circuit breaker is expressed in: — From PPSC Sub Engineer (Electrical) Exam, 2022

(A) Amperes

(B) Kiloamperes (symmetrical)

(C) Volts

(D) Watts

30. : An inverse time relay means: — From WAPDA Protection and Control Test, 2021

(A) Operating time decreases as current increases

(B) Operating time increases as current increases

(C) Constant operating time

(D) None of these

31. : The differential protection scheme is based on: — From FPSC Electrical Engineer Exam, 2020

(A) Kirchhoff’s voltage law

(B) Kirchhoff’s current law

(C) Faraday’s law

(D) Coulomb’s law

32. : In a transformer protection system, sudden pressure relays are used to detect: — From WAPDA Transformer Testing Exam, 2018

(A) Winding temperature rise

(B) Internal faults

(C) External short-circuit

(D) Overload condition

33. : Earth fault relays are operated by: — From PPSC Electrical Sub Engineer Test, 2021

(A) Phase current only

(B) Residual current

(C) Line-to-line voltage

(D) Power factor

34. : The circuit breakers used for 132 kV lines are generally: — From WAPDA Transmission Wing Exam, 2019

(A) Air-break type

(B) Oil circuit breakers

(C) Vacuum circuit breakers

(D) SF₆ circuit breakers

35. : A relay used for long transmission line protection is: — From PPSC Power System Engineer Paper, 2022

(A) Overcurrent relay

(B) Distance relay

(C) Differential relay

(D) Directional relay

36. : A lightning arrester is connected between: — From WAPDA Grid Station Operation Test, 2018

(A) Earth and load

(B) Line and earth

(C) Line and neutral

(D) Earth and neutral

37. : The operating principle of an induction relay is similar to that of: — From FPSC Electrical Engineer Exam, 2019

(A) Induction motor

(B) Synchronous motor

(C) Transformer

(D) Alternator

38. : An oil circuit breaker extinguishes the arc by: — From WAPDA Technical Services Test, 2020

(A) Cooling the arc and isolating the contacts

(B) Increasing the voltage

(C) Reducing pressure

(D) None of these

39. : The “Reset Ratio” of a relay is the ratio of: — From PPSC Protection Engineer Exam, 2020

(A) Pick-up current to reset current

(B) Reset current to pick-up current

(C) Operating time to reset time

(D) Fault current to normal current

40. : The function of a current transformer (CT) in protection system is to: — From WAPDA Grid Maintenance Exam, 2021

(A) Measure voltage

(B) Step down current for metering and relays

(C) Step up current

(D) Supply power to the load

41. : In a DC motor, the function of the commutator is to: — from WAPDA Junior Engineer Electrical Test 2018

(A) Reverse current direction in armature coil

(B) Reduce armature reaction

(C) Increase torque

(D) Cool the winding

42. : The power factor of an inductive circuit is: — from PPSC Sub Engineer Electrical 2019

(A) Leading

(B) Lagging

(C) Unity

(D) Zero

43. : The unit of magnetic flux density is: — from NTDC Engineer Electrical Test 2020

(A) Henry

(B) Weber

(C) Tesla

(D) Ohm

44. : Which law gives the relationship between voltage, current, and resistance? — from PPSC Electrical Inspector Exam 2017

(A) Coulomb’s Law

(B) Faraday’s Law

(C) Ohm’s Law

(D) Lenz’s Law

45. : The power output of a 3-phase motor is given by: — from FESCO Assistant Engineer Test 2021

(A) √3 × V × I × cosφ

(B) V × I × cosφ

(C) 3 × V × I × sinφ

(D) V² / R

46. : In transmission lines, corona loss increases with: — from WAPDA Electrical Engineer 2020

(A) Decrease in voltage

(B) Increase in voltage

(C) Decrease in frequency

(D) Decrease in temperature

47. : The transformer core is laminated to: — from PPSC Sub Engineer Electrical 2022

(A) Reduce hysteresis loss

(B) Reduce eddy current loss

(C) Reduce copper loss

(D) Reduce magnetic flux

48. : The speed of an induction motor can be controlled by: — from LESCO Junior Engineer Test 2019

(A) Varying stator frequency

(B) Varying rotor resistance

(C) Varying supply voltage

(D) All of the above

49. : The frequency of the supply in Pakistan is: — from PPSC Electrical Sub Engineer Exam 2018

(A) 50 Hz

(B) 60 Hz

(C) 25 Hz

(D) 100 Hz

50. : The insulation resistance of a good conductor is: — from MEPCO Technical Cadre Test 2021

(A) Very high

(B) Very low

(C) Zero

(D) Infinite

51. : The purpose of a step-up transformer is to: — from WAPDA Power Wing Exam 2019

(A) Decrease voltage

(B) Increase voltage

(C) Increase current

(D) Decrease frequency

52. : In a synchronous motor, the rotor speed is: — from PESCO Engineer Test 2020

(A) Greater than synchronous speed

(B) Less than synchronous speed

(C) Equal to synchronous speed

(D) Independent of frequency

53. : Which type of motor is used in ceiling fans? — from PPSC Electrical Supervisor 2021

(A) Induction motor

(B) DC shunt motor

(C) Synchronous motor

(D) Stepper motor

54. : The main function of a surge arrester is to: — from NTDC Electrical Engineer Test 2020

(A) Protect against lightning and switching surges

(B) Increase line voltage

(C) Reduce transmission losses

(D) Measure fault current

55. : The core of a power transformer is made of: — from PPSC Sub Engineer (Electrical) 2017

(A) Copper

(B) Aluminum

(C) Silicon steel

(D) Zinc

56. : The primary winding of a current transformer is connected in: — from FESCO Electrical Engineer Test 2021

(A) Series with the circuit

(B) Parallel with the circuit

(C) Across the load

(D) None of these

57. : The slip of an induction motor at no load is approximately: — from WAPDA Junior Engineer 2020

(A) 0%

(B) 2–5%

(C) 10%

(D) 100%

58. : The transmission voltage in Pakistan’s national grid is: — from NTDC Electrical Engineer Test 2021

(A) 132 kV, 220 kV, 500 kV

(B) 110 kV, 220 kV, 330 kV

(C) 66 kV, 132 kV, 400 kV

(D) 33 kV, 132 kV, 275 kV

59. : A capacitor stores energy in the form of: — from PPSC Electrical Test 2018

(A) Magnetic field

(B) Electric field

(C) Heat energy

(D) Chemical energy

60. : The open-circuit test on a transformer is used to measure: — from WAPDA Electrical Engineer 2019

(A) Iron losses

(B) Copper losses

(C) Total losses

(D) Efficiency

61. : Which protection device is used against overload in an electric circuit? — from PPSC Sub Engineer (Electrical) 2021

(A) Relay

(B) Circuit breaker

(C) Fuse

(D) Contactor

62. : The corona effect in transmission lines increases with: — from WAPDA Power Wing Test 2019

(A) Decrease in voltage

(B) Increase in conductor size

(C) Increase in operating voltage

(D) Decrease in line length

63. : A lightning arrester is connected: — from MEPCO Electrical Engineer Exam 2020

(A) In series with the line

(B) Between line and earth

(C) Across the circuit breaker

(D) Across transformer winding

64. : The power factor in a purely inductive circuit is: — from PPSC Electrical Inspector 2018

(A) Zero

(B) Unity

(C) Lagging

(D) Leading

65. : The efficiency of transmission increases by: — from NTDC Engineer Electrical Test 2021

(A) Increasing transmission voltage

(B) Decreasing power factor

(C) Using more resistive conductors

(D) Reducing voltage level

66. : In a 3-phase balanced system, the phase difference between two lines is: — from WAPDA Junior Engineer 2020

(A) 60°

(B) 90°

(C) 120°

(D) 180°

67. : A Buchholz relay is used for the protection of: — from PPSC Electrical Engineer 2019

(A) Transmission lines

(B) Induction motors

(C) Transformers

(D) Alternators

68. : The highest transmission voltage used in Pakistan is: — from NTDC Power System Test 2022

(A) 220 kV

(B) 400 kV

(C) 500 kV

(D) 765 kV

69. : Which of the following is not a transmission system component? — from LESCO Engineer Electrical 2021

(A) Transmission lines

(B) Transformer

(C) Circuit breaker

(D) Energy meter

70. : The term “Sag” in transmission lines refers to: — from MEPCO Sub Engineer Electrical 2020

(A) Vertical distance between conductor and ground

(B) Vertical distance between conductor and line joining supports

(C) Clearance between conductor and pole

(D) Length of conductor

71. : The current transformer (CT) ratio is expressed as: — from FESCO Electrical Engineer Test 2019

(A) Primary current / Secondary current

(B) Secondary current / Primary current

(C) Voltage ratio

(D) Power ratio

72. : The main function of an isolator is: — from PPSC Electrical Inspector Exam 2021

(A) Interrupt high fault currents

(B) Open a circuit under load

(C) Isolate a part of the circuit for maintenance

(D) Protect from lightning

73. : A synchronous condenser is used to: — from NTDC Transmission Engineer Exam 2018

(A) Improve power factor

(B) Reduce transmission losses

(C) Generate power

(D) Convert DC to AC

74. : In a 132 kV transmission system, the line-to-line voltage is 132 kV, then the line-to-neutral voltage is approximately: — from WAPDA Power Wing Test 2019

(A) 66 kV

(B) 76.2 kV

(C) 57.1 kV

(D) 132 kV

75. : The function of an earthing system is to: — from PPSC Sub Engineer (Electrical) 2020

(A) Provide an easy path for fault current

(B) Reduce circuit voltage

(C) Increase insulation resistance

(D) Increase load current

76. : The reactive power in AC circuits is measured in: — from MEPCO Electrical Engineer Exam 2022

(A) Watt

(B) Volt-Ampere

(C) Volt-Ampere Reactive (VAR)

(D) Joule

77. : Which device automatically isolates a circuit during fault conditions? — from PESCO Electrical Supervisor 2021

(A) Fuse

(B) Relay

(C) Circuit breaker

(D) Isolator

78. : The transmission efficiency is maximum when: — from WAPDA Technical Cadre Test 2020

(A) Line losses = Zero

(B) Transmission losses = Receiving end power

(C) Transmission losses = Receiving end power / 2

(D) Constant current flow

79. : A relay operates when: — from NTDC Protection Engineer Exam 2019

(A) Current exceeds preset value

(B) Frequency is stable

(C) Voltage is constant

(D) None of these

80. : The type of insulator used for 11 kV transmission lines is: — from PPSC Sub Engineer Electrical 2021

(A) Pin type

(B) Suspension type

(C) Strain type

(D) Shackle type