Past Papers Electrical Engineering PPSC

1. : The main component of thermal power plant is: — from WAPDA Electrical Engineer Exam 2019

(A) Boiler

(B) Cooling tower

(C) Condenser

(D) Alternator

2. : The function of the governor in a generator is to: — from PPSC Assistant Engineer (Electrical) 2020

(A) Maintain voltage

(B) Maintain frequency

(C) Increase torque

(D) Reduce load

3. : The efficiency of a thermal power plant is generally around: — from MEPCO Power Engineer Test 2021

(A) 15%–25%

(B) 30%–40%

(C) 50%–60%

(D) 70%–80%

4. : The primary fuel used in gas turbine power stations is: — from NTDC Electrical Engineer Exam 2020

(A) Coal

(B) Diesel

(C) Natural Gas

(D) Uranium

5. : The hydroelectric power plant converts: — from WAPDA Hydel Wing Test 2018

(A) Mechanical energy to electrical energy

(B) Potential energy to electrical energy

(C) Chemical energy to mechanical energy

(D) Kinetic energy to chemical energy

6. : The power generated at a thermal power station is usually at: — from PPSC Sub Engineer (Electrical) 2019

(A) 3.3 kV

(B) 6.6 kV

(C) 11 kV

(D) 33 kV

7. : In a transformer, the no-load current is: — from FESCO Electrical Engineer Test 2020

(A) Purely inductive

(B) Purely capacitive

(C) Purely resistive

(D) Lagging the voltage by an angle slightly less than 90°

8. : Which of the following parts is common to both DC machines and AC generators? — from WAPDA Power Division Test 2018

(A) Commutator

(B) Field winding

(C) Slip rings

(D) Rectifier

9. : The transformer does not work on DC supply because: — from NTDC Engineer Electrical Exam 2021

(A) No mutual induction in DC

(B) DC causes eddy currents

(C) DC reduces voltage

(D) DC increases resistance

10. : The efficiency of a transformer is maximum when: — from PPSC Electrical Inspector Test 2020

(A) Iron losses = Copper losses

Copper losses” onclick=”checkAnswer(‘q10’, ‘Iron losses = Copper losses’)”> (B) Iron losses > Copper losses

(C) Iron losses < Copper losses

(D) Load is full

11. : The open-circuit test on a transformer measures: — from MEPCO Technical Officer Exam 2019

(A) Iron losses

(B) Copper losses

(C) Total losses

(D) Short-circuit losses

12. : The short-circuit test on a transformer measures: — from PESCO Electrical Engineer Test 2021

(A) Copper losses

(B) Iron losses

(C) Voltage regulation

(D) Efficiency

13. : Which type of transformer is used in power transmission systems? — from NTDC Power System Test 2022

(A) Auto-transformer

(B) Step-up transformer

(C) Step-down transformer

(D) Isolation transformer

14. : The main function of an alternator is to: — from WAPDA Generation Wing Exam 2018

(A) Convert electrical energy to mechanical energy

(B) Convert mechanical energy to electrical energy

(C) Store energy

(D) Control frequency

15. : The number of poles in a 3000 rpm alternator working on 50 Hz is: — from PPSC Sub Engineer Electrical 2021

(A) 2

(B) 4

(C) 6

(D) 8

16. : The voltage regulation of an ideal transformer is: — from FESCO Junior Engineer Test 2020

(A) 0%

(B) 50%

(C) 100%

(D) 10%

17. : The armature reaction in a DC generator causes: — from PPSC Electrical Engineer Exam 2019

(A) Distortion of main field flux

(B) Increase in field flux

(C) Decrease in armature resistance

(D) Increase in commutation

18. : The efficiency of a DC motor is maximum when: — from WAPDA Junior Engineer 2020

(A) Copper losses = Constant losses

Iron losses” onclick=”checkAnswer(‘q18’, ‘Copper losses = Constant losses’)”> (B) Copper losses > Iron losses

(C) Copper losses < Iron losses

(D) None of these

19. : The function of carbon brushes in DC machines is to: — from MEPCO Sub Engineer Electrical 2021

(A) Conduct current between stationary and rotating parts

(B) Reduce friction

(C) Increase torque

(D) Improve insulation

20. : The synchronous speed of a 6-pole alternator operating at 50 Hz is: — from NTDC Electrical Engineer Test 2019

(A) 500 rpm

(B) 1000 rpm

(C) 1500 rpm

(D) 3000 rpm

21. : The instrument used for measuring electric potential difference is: — from PPSC Sub Engineer (Electrical) 2021

(A) Voltmeter

(B) Ammeter

(C) Wattmeter

(D) Ohmmeter

22. : A moving iron instrument can measure: — from WAPDA Electrical Engineer Test 2020

(A) DC only

(B) AC only

(C) Both AC and DC

(D) None of these

23. : Which instrument measures the power in an AC circuit? — from MEPCO Assistant Engineer Electrical 2021

(A) Ammeter

(B) Voltmeter

(C) Wattmeter

(D) Energy meter

24. : The power factor of a load can be measured by: — from NTDC Power Measurement Exam 2019

(A) Wattmeter method

(B) Dynamometer method

(C) Power factor meter

(D) Energy meter

25. : The device used to measure energy consumption in homes is: — from LESCO Metering Wing Test 2018

(A) Wattmeter

(B) Energy meter

(C) Power factor meter

(D) Potentiometer

26. : Which instrument works on the principle of electromagnetic induction? — from PPSC Sub Engineer (Electrical) 2020

(A) Electrodynamometer

(B) Energy meter

(C) Galvanometer

(D) Thermocouple ammeter

27. : A galvanometer can be converted into an ammeter by connecting: — from WAPDA Technical Cadre Test 2019

(A) High resistance in series

(B) Low resistance in parallel

(C) Low resistance in series

(D) High resistance in parallel

28. : A galvanometer can be converted into a voltmeter by connecting: — from PPSC Electrical Inspector Exam 2018

(A) High resistance in series

(B) Low resistance in parallel

(C) Inductor in parallel

(D) Capacitor in series

29. : The instrument used to measure insulation resistance is: — from MEPCO Sub Engineer Electrical 2022

(A) Voltmeter

(B) Ammeter

(C) Megger

(D) Multimeter

30. : The controlling torque in a moving coil instrument is provided by: — from WAPDA Electrical Engineer Test 2018

(A) Gravity

(B) Spring

(C) Eddy current

(D) Magnetic field

31. : The damping torque in a moving coil instrument is produced by: — from PESCO Electrical Test 2020

(A) Air friction

(B) Spring control

(C) Eddy currents

(D) Magnetic repulsion

32. : The function of a shunt in an ammeter is to: — from FESCO Junior Engineer Electrical 2019

(A) Carry most of the current

(B) Increase resistance

(C) Reduce current

(D) Provide insulation

33. : In a PMMC instrument, the deflection is proportional to: — from NTDC Electrical Engineer Test 2020

(A) Current

(B) Square of current

(C) Voltage

(D) Power

34. : Which type of instrument can measure instantaneous values? — from WAPDA Measurement & Control Exam 2021

(A) Indicating instrument

(B) Recording instrument

(C) Integrating instrument

(D) Null-type instrument

35. : The unit of capacitance is: — from PPSC Electrical Sub Engineer Exam 2021

(A) Ohm

(B) Farad

(C) Henry

(D) Volt

36. : The torque in an electrodynamometer type wattmeter is proportional to: — from NTDC Power Measurement Test 2019

(A) Product of voltage and current

(B) Square of voltage

(C) Square of current

(D) Resistance

37. : The principle of operation of LVDT is based on: — from PPSC Instrumentation Engineer 2020

(A) Capacitance

(B) Inductance

(C) Resistance

(D) Magnetic field

38. : In control systems, a feedback element is used to: — from WAPDA Control Systems Exam 2018

(A) Increase gain

(B) Reduce error

(C) Increase frequency

(D) Stabilize output voltage only

39. : Tachometer is used to measure: — from MEPCO Electrical Engineer Exam 2021

(A) Voltage

(B) Speed

(C) Torque

(D) Temperature

40. : The instrument used to measure phase difference between two waveforms is: — from PESCO Electrical Supervisor 2020

(A) Oscilloscope

(B) Multimeter

(C) Galvanometer

(D) Bridge circuit

41. : What is the main function of a transmission line? (PPSC Sub Engineer Electrical – 2022)

(A) To generate power

(B) To transfer electric power from generating stations to substations

(C) To measure current

(D) To control voltage fluctuations

42. : What is the surge impedance of a transmission line? (WAPDA Electrical Engineer – 2020)

(A) Ratio of voltage to resistance

(B) Ratio of voltage to current under surge conditions

(C) Product of current and voltage

(D) None of these

43. : Which among the following materials is commonly used for overhead transmission lines? (PPSC Assistant Engineer Electrical – 2021)

(A) Copper

(B) Aluminium

(C) Silver

(D) Iron

44. : What is Ferranti effect? (WAPDA Electrical Engineer – 2019)

(A) Voltage drop along the line

(B) Voltage rise at the receiving end during light load

(C) Power loss due to corona

(D) Power factor improvement

45. : What is the skin effect in transmission lines? (PPSC Electrical Engineer – 2020)

(A) Increase in current density at the center of the conductor

(B) Decrease in current density near the surface of the conductor

(C) Increase in current density near the surface of the conductor

(D) Uniform current distribution

46. : The corona loss in transmission lines increases with? (LESCO Engineer Recruitment Test – 2021)

(A) Decrease in line voltage

(B) Increase in frequency

(C) Decrease in conductor spacing

(D) Both (B) and (C)

47. : Which type of insulator is used for very high voltage transmission lines? (PPSC Sub Engineer Electrical – 2022)

(A) Pin type

(B) Suspension type

(C) Shackle type

(D) Strain type

48. : What is the main function of a Buchholz relay? (WAPDA Electrical Engineer – 2020)

(A) Detect overheating in alternator

(B) Detect internal faults in transformers

(C) Measure power factor

(D) Protect induction motor

49. : The efficiency of a transmission line is maximum when? (PPSC Assistant Electrical Engineer – 2021)

(A) Sending end voltage = Receiving end voltage

(B) Line losses are zero

(C) Total losses = Reactive power loss

(D) Variable loss = Constant loss

50. : The dielectric strength of transformer oil should be at least? (NTDC Electrical Engineer – 2023)

(A) 5 kV

(B) 15 kV

(C) 30 kV

(D) 50 kV

51. : The synchronous speed of a 4-pole alternator operating at 50 Hz is? (PPSC Electrical Engineer – 2021)

(A) 1500 rpm

(B) 3000 rpm

(C) 1000 rpm

(D) 750 rpm

52. : In thermal power plants, the prime mover is usually? (WAPDA Assistant Engineer Electrical – 2020)

(A) Diesel engine

(B) Gas turbine

(C) Steam turbine

(D) Hydraulic turbine

53. : In a hydroelectric power station, the energy of water is converted into? (PPSC Sub Engineer Electrical – 2022)

(A) Heat energy

(B) Kinetic energy

(C) Electrical energy

(D) Mechanical energy

54. : The function of a surge tank in a hydroelectric plant is to? (WAPDA Electrical Engineer – 2019)

(A) Store excess water

(B) Control water hammer pressure

(C) Increase turbine speed

(D) Reduce head losses

55. : Which generating station has the minimum running cost? (LESCO Junior Engineer Test – 2021)

(A) Thermal power plant

(B) Nuclear power plant

(C) Hydro power plant

(D) Gas turbine plant

56. : The power factor of an inductive load is usually? (PPSC Electrical Sub Engineer – 2020)

(A) Leading

(B) Lagging

(C) Unity

(D) Zero

57. : The major disadvantage of a nuclear power plant is? (WAPDA Electrical Engineer – 2021)

(A) High fuel cost

(B) Air pollution

(C) Disposal of radioactive waste

(D) Large land requirement

58. : Which instrument is used to measure insulation resistance? (PPSC Assistant Engineer Electrical – 2022)

(A) Megger

(B) Voltmeter

(C) Wattmeter

(D) Multimeter

59. : The earth resistance of a good earthing system should be less than? (NTDC Electrical Engineer – 2023)

(A) 1 ohm

(B) 5 ohms

(C) 10 ohms

(D) 20 ohms

60. : A fuse in an electrical circuit is used to? (WAPDA Sub Engineer Electrical – 2022)

(A) Prevent short circuit

(B) Prevent overcurrent damage

(C) Prevent voltage drop

(D) Increase current flow

61. : A 3-phase alternator generates a line voltage of 11 kV. The phase voltage will be approximately? (PPSC Electrical Engineer – 2022)

(A) 11 kV

(B) 6.35 kV

(C) 19 kV

(D) 3.81 kV

62. : In a DC generator, the armature reaction causes? (WAPDA Electrical Engineer – 2021)

(A) Increase in main flux

(B) Decrease in main flux

(C) No effect on main flux

(D) Distortion of main flux only

63. : In power systems, diversity factor is always? (PPSC Electrical Sub Engineer – 2020)

(A) Less than 1

(B) Equal to 1

(C) Greater than 1

(D) Zero

64. : In a distribution system, feeders are designed mainly for? (LESCO Sub Engineer Electrical – 2022)

(A) Voltage drop

(B) Current carrying capacity

(C) Power factor

(D) Frequency

65. : The frequency of the generated voltage in an alternator depends on? (WAPDA Assistant Engineer – 2020)

(A) Armature current

(B) Number of poles and speed

(C) Field resistance

(D) Load power factor

66. : In electrical safety, the purpose of earthing is to? (NTDC Electrical Engineer – 2023)

(A) Increase resistance

(B) Protect equipment and personnel from shock

(C) Improve insulation

(D) Store charge

67. : A circuit breaker is used to? (PPSC Assistant Engineer Electrical – 2021)

(A) Protect electrical circuits from overload and short circuit faults

(B) Convert AC to DC

(C) Measure voltage

(D) Increase power factor

68. : The medium used for arc extinction in an oil circuit breaker is? (WAPDA Electrical Engineer – 2020)

(A) Air

(B) SF₆ gas

(C) Transformer oil

(D) Water

69. : In SF₆ circuit breakers, the gas SF₆ acts as? (NTDC Electrical Engineer – 2023)

(A) Cooling and insulating medium

(B) Fuel

(C) Magnetic medium

(D) Conductor

70. : Which protective device is used to protect a transformer from internal faults? (WAPDA Assistant Engineer Electrical – 2019)

(A) Lightning arrester

(B) Buchholz relay

(C) Fuse

(D) Earth relay

71. : The rating of a circuit breaker is generally expressed in? (PPSC Sub Engineer Electrical – 2022)

(A) kW and power factor

(B) Amperes, kV, and MVA

(C) Volts only

(D) Current only

72. : The main purpose of a lightning arrester is to? (LESCO Electrical Engineer – 2021)

(A) Protect equipment from lightning overvoltages

(B) Prevent earth fault currents

(C) Improve load factor

(D) Maintain constant frequency

73. : Relay used for detecting earth faults is generally a? (WAPDA Electrical Engineer – 2020)

(A) Differential relay

(B) Overcurrent relay

(C) Earth leakage relay

(D) Reverse power relay

74. : A thermal overload relay works on the principle of? (PPSC Electrical Engineer – 2022)

(A) Electromagnetic induction

(B) Heating effect of current

(C) Chemical reaction

(D) Magnetic flux density

75. : Which type of relay is used for the protection of transmission lines? (NTDC Assistant Engineer – 2023)

(A) Differential relay

(B) Distance relay

(C) Buchholz relay

(D) Thermal relay

76. : The term “pick-up current” of a relay means? (PPSC Sub Engineer Electrical – 2021)

(A) Maximum current the relay can carry

(B) Minimum current required to operate the relay

(C) Current required to reset the relay

(D) Rated current of the relay

77. : The main function of a current transformer (CT) is to? (WAPDA Electrical Engineer – 2019)

(A) Step up voltage

(B) Step down current for measurement and protection

(C) Increase power

(D) Improve efficiency

78. : The primary winding of a current transformer is connected in? (PPSC Electrical Engineer – 2022)

(A) Series with the line

(B) Parallel with the line

(C) Across the load

(D) Between two phases

79. : A potential transformer (PT) is used for? (LESCO Junior Engineer – 2021)

(A) Measuring high voltages

(B) Measuring high currents

(C) Power factor correction

(D) Frequency control

80. : SF₆ circuit breakers are preferred because they have? (NTDC Electrical Engineer – 2023)

(A) High dielectric strength and arc-quenching ability

(B) Low cost and high losses

(C) Large size and heavy weight

(D) Low reliability