1. : The SI unit of electric current is? — from WAPDA / PPSC past MCQs
(A) Volt
(B) Ohm
(C) Ampere
(D) Coulomb
2. : Ohm’s law is given by? — from WAPDA / PPSC past MCQs
(A) V = I × R
(B) I = V × R
(C) R = I × V
(D) V = I / R
3. : Which of the following is the unit of resistance? — from WAPDA / PPSC past MCQs
(A) Ampere
(B) Volt
(C) Ohm
(D) Henry
4. : The surge impedance of a transmission line is: (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
5. : The principle on which a transformer works is? — from WAPDA / PPSC past MCQs
(A) Ohm’s Law
(B) Mutual Induction
(C) Self Induction
(D) Electromagnetic Force
6. : Slip of an induction motor is: — from WAPDA / PPSC past MCQs
(A) Always 0
(B) Always 1
(C) Less than 1
(D) More than 1
7. : A battery can supply 110 joules of energy to move 10 coulombs of charge. What is the voltage of the battery? — from Junior Engineer (Electrical) Sample Paper, PPSC 2022
(A) 10 V
(B) 11 V
(C) 110 V
(D) 1.10 V
8. : A 3-phase, 50 Hz, 6-pole synchronous motor rotates at: — from Junior Engineer (Electrical) Sample Paper, PPSC 2022
(A) 1000 rpm
(B) 1500 rpm
(C) 1800 rpm
(D) 3600 rpm
9. : Which law states that the current through a conductor between two points is proportional to the voltage across the two points? — from WAPDA / PPSC past MCQs
(A) Faraday’s Law
(B) Ohm’s Law
(C) Lenz’s Law
(D) Kirchhoff’s Voltage Law
10. : What is the power factor in an AC circuit defined as? — from WAPDA / PPSC past MCQs
(A) Active power / Apparent power
(B) Apparent power / Active power
(C) Reactive power / Active power
(D) Active × Reactive
11. : Which winding of a transformer has lower cross-sectional area? — from “Electrical Engineering MCQs – list of repeated NTS MCQs”
Scribd
(A) Primary winding
(B) Secondary winding
(C) Both are equal
12. : What is the frequency of AC supply in Pakistan? — from WAPDA / PPSC MCQs collection
(A) 60 Hz
(B) 50 Hz
(C) 100 Hz
(D) 25 Hz
13. : A 3-phase, 50 Hz, 4-pole induction motor’s synchronous speed is: — from Sample Paper Junior Engineer Electrical, PPSC (sample) 2022
Scribd
(A) 1200 rpm
(B) 1500 rpm
(C) 1000 rpm
14. : The test “Junior Engineer (Electrical)” for WAPDA / PTS was held on 22 May, 2022 — in that test, a question asked: Depletion region in a PN semiconductor is due to? — from WAPDA Junior Engineer Test PTS 2022 (Electronics), 22 May 2022
TEC
(A) Mobile donor & acceptor ions
(B) Free electrons only
(C) Holes only
15. : From WAPDA Test Preparation Material, Junior Engineer Power (Electrical), Past Paper 2018 — which of the following is the unit of resistivity? — WAPDA JE Power past 2018
Scribd
(A) Ohm · meter
(B) Siemens per meter
(C) Farad per meter
16. : From SPSC Sub Engineer Electrical (BPS-11) past MCQs — the document contains questions on motors, capacitors, etc. — one such question: which of the following is NOT a part of a synchronous generator? — from SPSC Test MCQs Sub Engineer Electrical, BPS-11
Scribd
(A) Rotor
(B) Stator
(C) Commutator
17. : In a DC machine, the commutator converts? — from PPSC Sub Engineer (Electrical) 2021
(A) AC to DC
(B) DC to AC
(C) Mechanical to Electrical
(D) Electrical to Mechanical
18. : The main function of a starter in a DC motor is? — from WAPDA Junior Engineer (Electrical) 2019
(A) To increase speed
(B) To reduce starting current
(C) To maintain torque
(D) To control voltage
19. : The material used for the filament of an electric bulb is? — from PPSC Electrical Engineer (BS-17) 2020
(A) Carbon
(B) Copper
(C) Tungsten
(D) Aluminium
20. : The main disadvantage of a capacitor start motor is? — from PPSC Sub Engineer (Electrical) 2018
(A) High cost
(B) Low starting torque
(C) High maintenance
(D) Poor efficiency
21. : The efficiency of a transformer is maximum when? — from WAPDA JE (Electrical) 2020
(A) Iron loss = Copper loss
Copper loss” onclick=”checkAnswer(‘q21’, ‘Iron loss = Copper loss’)”> (B) Iron loss > Copper loss
Iron loss” onclick=”checkAnswer(‘q21’, ‘Iron loss = Copper loss’)”> (C) Copper loss > Iron loss
(D) Core loss = 0
22. : Which instrument measures both AC and DC currents? — from PPSC AE (Electrical) 2019
(A) Moving iron instrument
(B) Hot wire instrument
(C) Dynamometer type instrument
(D) Permanent magnet type instrument
23. : The frequency of generated voltage in an alternator depends on? — from PPSC JE Electrical 2022
(A) Speed of rotor and number of poles
(B) Type of core
(C) Size of stator
(D) Voltage applied
24. : In transmission lines, skin effect increases with? — from WAPDA Sub Engineer (Electrical) 2020
(A) Decrease in frequency
(B) Increase in frequency
(C) Decrease in voltage
(D) Decrease in current
25. : The insulation resistance of a cable should be measured by? — from PPSC Electrical Inspector 2021
(A) Ammeter
(B) Voltmeter
(C) Megger
(D) Ohmmeter
26. : The purpose of a surge arrester in a substation is to? — from WAPDA Assistant Engineer (Electrical) 2019
(A) Absorb switching surges
(B) Protect equipment from lightning
(C) Increase voltage level
(D) Reduce harmonics
27. : A three-phase balanced load draws a total power of 9 kW at unity power factor. The power per phase is? — from PPSC JE Electrical 2020
(A) 1.5 kW
(B) 2 kW
(C) 3 kW
(D) 4.5 kW
28. : The function of a choke coil in a fluorescent lamp is to? — from WAPDA Sub Engineer (Electrical) 2018
(A) Increase current
(B) Decrease voltage
(C) Limit current
(D) Rectify current
29. : In a synchronous motor, when load increases, the armature current? — from PPSC AE Electrical 2021
(A) Decreases
(B) Increases
(C) Remains constant
(D) Becomes zero
30. : The core of a transformer is laminated to? — from WAPDA Junior Engineer (Electrical) 2017
(A) Reduce copper loss
(B) Reduce eddy current loss
(C) Reduce hysteresis loss
(D) Increase efficiency only
31. : The power factor of a purely inductive circuit is? — from WAPDA JE (Electrical) 2020
(A) 0
(B) 0.5
(C) 1
(D) 0.707
32. : The device used to convert AC to DC is called? — from PPSC Sub Engineer (Electrical) 2021
(A) Inverter
(B) Transformer
(C) Rectifier
(D) Amplifier
33. : For maximum power transfer, the load resistance must be? — from PPSC AE Electrical 2022
(A) Equal to source resistance
(B) Half of source resistance
(C) Double of source resistance
(D) Negligible
34. : In a 3-phase system, the phase difference between the voltages of any two phases is? — from WAPDA Sub Engineer (Electrical) 2019
(A) 60°
(B) 90°
(C) 120°
(D) 180°
35. : Which type of motor is used in ceiling fans? — from PPSC Sub Engineer Electrical 2020
(A) Shaded pole motor
(B) Universal motor
(C) Capacitor start motor
(D) Induction motor
36. : The insulation used in high voltage cables is usually made of? — from WAPDA JE Power 2019
(A) PVC
(B) Cotton
(C) Paper
(D) Rubber
37. : What does “LVDT” stand for in measurement systems? — from PPSC Electrical Inspector 2022
(A) Linear Variable Differential Transformer
(B) Linear Voltage Distribution Transistor
(C) Load Voltage Detector Transmitter
(D) Level Variable Detection Transformer
38. : The main function of a breather in a transformer is to? — from WAPDA Assistant Engineer (Electrical) 2020
(A) Filter air entering the conservator tank
(B) Cool transformer oil
(C) Prevent oil leakage
(D) Maintain voltage
39. : The device used to measure very high resistance is? — from PPSC AE Electrical 2021
(A) Megger
(B) Wheatstone Bridge
(C) Ohmmeter
(D) Multimeter
40. : In an RLC circuit, at resonance the impedance is? — from WAPDA Sub Engineer (Electrical) 2018
(A) Minimum
(B) Maximum
(C) Infinite
(D) Zero
41. : When two resistors of 4 Ω and 6 Ω are connected in parallel, their equivalent resistance is? — from PPSC Sub Engineer (Electrical) 2021
(A) 2.4 Ω
(B) 10 Ω
(C) 4 Ω
(D) 6 Ω
42. : The color code of a resistor with bands: Red, Violet, Yellow, and Gold represents? — from PPSC JE Electrical 2022
(A) 27 kΩ ±5%
(B) 270 kΩ ±5%
(C) 270 kΩ ±10%
(D) 2.7 MΩ ±5%
43. : Which component stores electrical energy in an electric field? — from WAPDA JE Electrical 2019
(A) Resistor
(B) Inductor
(C) Capacitor
(D) Transformer
44. : The function of a fuse is to? — from PPSC Electrical Engineer (BS-17) 2021
(A) Prevent overcurrent
(B) Increase current
(C) Decrease voltage
(D) Store charge
45. : In transmission systems, corona effect can be reduced by? — from WAPDA Sub Engineer (Electrical) 2020
(A) Decreasing conductor diameter
(B) Increasing spacing between conductors
(C) Increasing voltage
(D) Using bare conductors
46. : The open-circuit test of a transformer gives information about? — from PPSC AE Electrical 2019
(A) Iron losses
(B) Copper losses
(C) Total losses
(D) Leakage reactance
47. : The primary and secondary windings of a transformer should have? — from WAPDA JE Electrical 2021
(A) Magnetic coupling
(B) Electrical connection
(C) Resistive coupling
(D) Inductive reactance
48. : A synchronous motor runs at? — from PPSC Sub Engineer (Electrical) 2018
(A) Below synchronous speed
(B) Above synchronous speed
(C) Exactly synchronous speed
(D) Variable speed
49. : The instrument used for measuring alternating current is? — from WAPDA JE Power 2020
(A) PMMC meter
(B) Hot wire meter
(C) Digital frequency meter
(D) Magnetic compass
50. : Which type of system is used for long-distance high-voltage transmission? — from PPSC Electrical Engineer 2021
(A) DC system
(B) AC system
(C) Hybrid system
(D) Static system
51. : The voltage across a resistor and current through it are in? — from WAPDA Sub Engineer (Electrical) 2019
(A) Phase opposition
(B) Same phase
(C) Quadrature
(D) 90° lag
52. : A 10 Ω resistor carries a current of 2 A. The power dissipated is? — from PPSC JE Electrical 2021
(A) 10 W
(B) 20 W
(C) 40 W
(D) 4 W
53. : The efficiency of a transmission line increases when? — from PPSC AE (Electrical) 2020
(A) Line losses decrease
(B) Load increases
(C) Voltage decreases
(D) Frequency increases
54. : In a parallel RLC circuit at resonance, the current through the resistor is? — from WAPDA JE Power 2019
(A) Minimum
(B) Maximum
(C) Zero
(D) Infinite
55. : For high voltage transmission, the line current is reduced by? — from PPSC Electrical Engineer 2021
(A) Increasing voltage
(B) Decreasing voltage
(C) Increasing frequency
(D) Decreasing power factor
56. : The controlling torque in a moving-coil instrument is provided by? — from WAPDA JE Electrical 2020
(A) Gravity control
(B) Spring control
(C) Air friction
(D) Damping magnets
57. : The main reason for providing a tap changer in a transformer is to? — from PPSC AE Electrical 2021
(A) Adjust output voltage
(B) Change frequency
(C) Control flux
(D) Reduce copper loss
58. : The unit of magnetic flux is? — from PPSC Sub Engineer (Electrical) 2018
(A) Tesla
(B) Weber
(C) Henry
(D) Maxwell
59. : The term “load factor” in power systems is defined as? — from WAPDA Assistant Engineer (Electrical) 2019
(A) Average load / Maximum load
(B) Maximum load / Average load
(C) Average load × Maximum load
(D) Load per unit voltage
60. : The maximum demand of a consumer is 10 kW and energy consumption in a day is 120 kWh. The load factor is? — from PPSC JE Electrical 2022
(A) 0.25
(B) 0.50
(C) 0.75
(D) 0.60
61. : In a synchronous generator, the rotating part is called? — from WAPDA JE Power 2020
(A) Stator
(B) Rotor
(C) Armature
(D) Field winding
62. : The efficiency of a DC generator is maximum when? — from PPSC Sub Engineer Electrical 2019
(A) Variable losses = Constant losses
(B) Copper loss = Iron loss
(C) Constant loss = Zero
(D) Core loss = Armature loss
63. : The insulation level of a 220 kV transmission line is usually designed for? — from WAPDA Assistant Engineer Electrical 2018
(A) 230 kV
(B) 245 kV
(C) 260 kV
(D) 300 kV
64. : In a CRO, the vertical deflection represents? — from PPSC Electrical Engineer 2021
(A) Current
(B) Voltage
(C) Frequency
(D) Time
65. : The dielectric strength of air is approximately? — from WAPDA JE Power 2020
(A) 3 kV/mm
(B) 10 kV/mm
(C) 30 kV/mm
(D) 100 kV/mm
66. : The short-circuit test on a transformer is conducted to find? — from PPSC AE Electrical 2019
(A) Copper losses
(B) Iron losses
(C) Hysteresis losses
(D) Core losses
67. : What is the 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
68. : A capacitor allows AC to pass but blocks DC because? — from PPSC JE Electrical 2020
(A) AC changes polarity continuously
(B) DC has constant polarity
(C) Both (A) and (B)
(D) None of these
69. : The most commonly used material for fuse wire is? — from WAPDA JE Power 2018
(A) Silver
(B) Copper
(C) Tin-lead alloy
(D) Aluminium
70. : A transmission line has a sending-end voltage of 220 kV and receiving-end voltage of 200 kV. The voltage regulation is approximately? — from PPSC AE Electrical 2021
(A) 5%
(B) 8%
(C) 9%
(D) 10%
71. : The semiconductor used in most electronic devices is? — from Sub Engineer (Electrical) PPSC 2020
(A) Germanium
(B) Silicon
(C) Gallium Arsenide
(D) Selenium
72. : The depletion region in a PN junction acts as a: — from WAPDA Junior Engineer Test 2019
(A) Conductor
(B) Insulator
(C) Resistor
(D) Capacitor
73. : The forward bias in a diode causes the current to: — from PPSC Electrical Engineer Test 2021
(A) Increase
(B) Stop
(C) Reverse
(D) Remain zero
74. : A Zener diode is primarily used for: — from WAPDA Electrical Sub Engineer 2018
(A) Rectification
(B) Voltage Regulation
(C) Amplification
(D) Switching
75. : In a transistor, the base region is: — from PPSC Electrical Engineer 2022
(A) Heavily doped and thick
(B) Lightly doped and thin
(C) Heavily doped and thin
(D) Lightly doped and thick
76. : The main function of a rectifier is to: — from WAPDA Technical Cadre Exam 2020
(A) Convert AC to DC
(B) Convert DC to AC
(C) Increase voltage
(D) Decrease voltage
77. : The ripple factor of a pure DC signal is: — from Sub Engineer (Electrical) PPSC 2021
(A) 1
(B) 0
(C) 0.707
(D) 2
78. : In a full-wave rectifier, how many diodes are used? — from WAPDA Electrical Engineer 2019
(A) 1
(B) 2
(C) 3
(D) 4
79. : The function of a capacitor in an electronic circuit is to: — from PPSC Electrical Sub Engineer 2020
(A) Store electric charge
(B) Store magnetic field
(C) Reduce resistance
(D) Amplify signal
80. : The unit of capacitance is: — from WAPDA Electrical Test 2021
(A) Henry
(B) Farad
(C) Ohm
(D) Tesla
81. : In a power system, a circuit breaker is used to: — from PPSC Assistant Engineer (Power) 2022
(A) Regulate voltage
(B) Interrupt fault current
(C) Step up current
(D) Maintain frequency
82. : The Buchholz relay is used for the protection of: — from WAPDA Power Division Test 2018
(A) Transmission Line
(B) Transformer
(C) Generator
(D) Induction Motor
83. : Lightning arresters are installed to protect equipment from: — from Sub Engineer (Electrical) PPSC 2019
(A) Overload
(B) Overvoltage
(C) Undervoltage
(D) Frequency Variation
84. : The relay used for detecting overcurrent in power systems is: — from WAPDA Electrical Engineer Test 2020
(A) Differential Relay
(B) Thermal Relay
(C) Electromagnetic Relay
(D) Overcurrent Relay
85. : The speed of an alternator is inversely proportional to: — from PPSC Electrical Engineer Exam 2018
(A) Frequency
(B) Voltage
(C) Number of poles
(D) Power Factor
86. : The frequency of generated voltage in a 4-pole alternator rotating at 1500 rpm is: — from WAPDA Power Generation Exam 2021
(A) 25 Hz
(B) 50 Hz
(C) 100 Hz
(D) 75 Hz
87. : Synchronous speed formula is given by Ns = ? — from Sub Engineer (Electrical) PPSC 2020
(A) 60f / P
(B) 120f / P
(C) 30f / P
(D) f / 2P
88. : In hydroelectric power plants, the energy of water is converted into: — from WAPDA Hydel Wing Test 2019
(A) Chemical Energy
(B) Thermal Energy
(C) Electrical Energy
(D) Mechanical Energy
89. : The alternator converts: — from PPSC Junior Engineer (Electrical) 2020
(A) Electrical energy into mechanical energy
(B) Mechanical energy into electrical energy
(C) Chemical energy into electrical energy
(D) Thermal energy into electrical energy
90. : In thermal power plants, coal is mainly used as: — from WAPDA Generation Division Test 2020
(A) Catalyst
(B) Fuel
(C) Coolant
(D) Insulator
91. : The main component of a nuclear reactor is: — from PPSC Energy Department Exam 2022
(A) Turbine
(B) Control Rod
(C) Condenser
(D) Alternator
92. : Which of the following is a renewable energy source? — from WAPDA Power Wing Test 2021
(A) Coal
(B) Solar
(C) Diesel
(D) Natural Gas
93. : The efficiency of a thermal power plant is usually between: — from Sub Engineer (Electrical) PPSC 2021
(A) 15–25%
(B) 25–35%
(C) 35–45%
(D) 45–55%
94. : In power transmission, high voltage is preferred to reduce: — from WAPDA Power Transmission Test 2019
(A) Current
(B) Resistance
(C) Voltage
(D) Power
95. : Transmission lines are used to carry electrical energy from? — from PPSC Electrical Sub Engineer 2021
(A) Consumer to Power Station
(B) Power Station to Substation
(C) Substation to Transformer
(D) Generator to Battery
96. : The main advantage of high-voltage transmission is: — from WAPDA Transmission Test 2020
(A) Reduction in current and losses
(B) Increase in power losses
(C) Increase in current
(D) Easier insulation
97. : The corona effect in transmission lines causes: — from PPSC Electrical Engineer Exam 2019
(A) Decrease in transmission efficiency
(B) Increase in current
(C) Increase in frequency
(D) Voltage regulation improvement
98. : The power factor of a purely capacitive circuit is: — from WAPDA Electrical Test 2018
(A) 1 lagging
(B) 1 leading
(C) Zero
(D) 0.5
99. : The skin effect in a conductor increases with: — from PPSC Junior Engineer (Electrical) 2020
(A) Increase in frequency
(B) Decrease in frequency
(C) Increase in current
(D) Decrease in voltage
100. : Ferranti effect is prominent in: — from WAPDA Transmission Line Exam 2019
(A) Short transmission lines
(B) Medium transmission lines
(C) Long transmission lines
(D) None of these
101. : A 3-phase balanced system has how many line conductors? — from PPSC Electrical Sub Engineer 2021
(A) 2
(B) 3
(C) 4
(D) 6
102. : A DC generator converts: — from WAPDA Electrical Engineer Test 2018
(A) Electrical to mechanical energy
(B) Mechanical to electrical energy
(C) Thermal to electrical energy
(D) Chemical to mechanical energy
103. : The part of a DC generator where EMF is induced is called: — from PPSC Electrical Engineer Exam 2020
(A) Field winding
(B) Commutator
(C) Armature
(D) Yoke
104. : The purpose of a commutator in a DC machine is to: — from WAPDA Technical Cadre Test 2019
(A) Reverse current direction
(B) Increase voltage
(C) Reduce resistance
(D) Increase torque
105. : In a DC motor, back EMF is directly proportional to: — from PPSC Sub Engineer Electrical 2022
(A) Supply voltage
(B) Speed of the motor
(C) Torque
(D) Armature resistance
106. : Which type of motor is commonly used in electric trains? — from WAPDA Power Wing Test 2021
(A) DC shunt motor
(B) DC series motor
(C) Induction motor
(D) Stepper motor
107. : In an induction motor, the rotor speed is always: — from PPSC Electrical Engineer Exam 2018
(A) Equal to synchronous speed
(B) Less than synchronous speed
(C) More than synchronous speed
(D) Zero
108. : The slip of an induction motor is zero when: — from WAPDA Technical Test 2020
(A) Motor is running at synchronous speed
(B) Motor is running at no load
(C) Motor is stopped
(D) Motor is overloaded
109. : The starting torque of an induction motor is increased by: — from PPSC Electrical Engineer 2020
(A) Adding external resistance in rotor circuit
(B) Increasing supply frequency
(C) Decreasing voltage
(D) Increasing stator resistance
110. : In a transformer, no-load current is: — from WAPDA Power Transformer Exam 2019
(A) Small and lagging the voltage
(B) Large and leading the voltage
(C) Large and lagging the voltage
(D) Small and leading the voltage
111. : The open-circuit test of a transformer is used to measure: — from PPSC Electrical Engineer Test 2021
(A) Copper losses
(B) Iron losses
(C) Efficiency
(D) Voltage regulation
112. : The short-circuit test of a transformer is used to measure: — from WAPDA Transformer Maintenance Exam 2020
(A) Iron losses
(B) Copper losses
(C) Voltage ratio
(D) Efficiency
113. : The main cause of hysteresis loss in a transformer core is: — from PPSC Sub Engineer Electrical 2019
(A) Reversal of magnetization
(B) Leakage flux
(C) Eddy currents
(D) Poor insulation
114. : The efficiency of a transformer is maximum when: — from WAPDA Electrical Engineer Exam 2021
(A) Copper losses = Iron losses
(B) Copper losses < Iron losses
Iron losses” onclick=”checkAnswer(‘q114’, ‘Copper losses = Iron losses’)”> (C) Copper losses > Iron losses
(D) Load is full
115. : The instrument used to measure voltage is called? — from PPSC Sub Engineer (Electrical) 2021
(A) Ammeter
(B) Wattmeter
(C) Voltmeter
(D) Ohmmeter
116. : A galvanometer can be converted into an ammeter by connecting a: — from WAPDA Technical Cadre Exam 2020
(A) High resistance in parallel
(B) Low resistance in parallel
(C) High resistance in series
(D) Low resistance in series
117. : A wattmeter measures: — from PPSC Electrical Engineer Test 2019
(A) Apparent power only
(B) Real power only
(C) Reactive power only
(D) Power factor
118. : The SI unit of electric charge is: — from WAPDA Electrical Engineer Exam 2018
(A) Volt
(B) Coulomb
(C) Ampere
(D) Joule
119. : Megger is used for measuring: — from PPSC Electrical Sub Engineer 2020
(A) Low resistance
(B) Medium resistance
(C) High resistance or insulation resistance
(D) Current
120. : The working principle of a moving coil instrument is based on: — from WAPDA Technical Test 2019
(A) Magnetic effect of current
(B) Chemical effect of current
(C) Thermal effect of current
(D) Inductive effect of current
121. : The bridge used for measuring unknown inductance is: — from PPSC Electrical Engineer Exam 2021
(A) Wheatstone bridge
(B) Maxwell bridge
(C) Schering bridge
(D) Anderson bridge
122. : The controlling torque in a PMMC instrument is provided by: — from WAPDA Electrical Test 2020
(A) Gravity control
(B) Spring control
(C) Air friction
(D) Magnetic field
123. : Which instrument uses hot wire for measurement? — from PPSC Electrical Sub Engineer 2019
(A) Thermocouple ammeter
(B) PMMC voltmeter
(C) Dynamometer wattmeter
(D) Induction wattmeter
124. : In control systems, feedback is used to: — from WAPDA Control System Exam 2021
(A) Increase error
(B) Reduce stability
(C) Reduce error and improve accuracy
(D) Increase system gain only
125. : A system is said to be stable if: — from PPSC Electrical Engineer 2020
(A) Output oscillates continuously
(B) Output remains bounded for bounded input
(C) Output tends to infinity
(D) Gain is infinite
126. : The Laplace transform is commonly used in control systems for: — from WAPDA Automation & Control Test 2018
(A) Frequency domain analysis
(B) Time domain analysis
(C) Nonlinear modeling
(D) Fault location
127. : The transfer function of a control system represents: — from PPSC Electrical Sub Engineer 2022
(A) Input–output relationship
(B) Power consumption
(C) Voltage ratio
(D) Time constant
128. : In Bode plot, the slope of a single-pole system is: — from WAPDA Control Engineering Test 2020
(A) -10 dB/decade
(B) -20 dB/decade
(C) -30 dB/decade
(D) -40 dB/decade
129. : Nyquist stability criterion is used to determine: — from PPSC Electrical Engineer Exam 2021
(A) Transient response
(B) System stability
(C) Steady-state error
(D) Time constant
130. : The bandwidth of an amplifier is defined as: — from WAPDA Electronics Section Test 2019
(A) Range of frequencies over which gain remains constant
(B) Maximum frequency only
(C) Minimum frequency only
(D) Product of voltage and current
131. : AM (Amplitude Modulation) is used in: — from PPSC Communication Systems Exam 2020
(A) Television
(B) FM radio
(C) Long-distance radio transmission
(D) Microwave communication
132. : The main advantage of FM over AM is: — from WAPDA Communication Engineering Test 2021
(A) Simpler circuits
(B) Better noise immunity
(C) Higher power requirement
(D) Lower bandwidth
133. : The range of audible frequency for human ear is: — from PPSC Electrical Engineer 2019
(A) 20 Hz to 2000 Hz
(B) 20 Hz to 20000 Hz
(C) 2 Hz to 200 Hz
(D) 2000 Hz to 20000 Hz
134. : The process of converting digital signal to analog signal is known as: — from WAPDA Communication & Control Test 2022
(A) Sampling
(B) Modulation
(C) Demodulation
(D) Reconstruction
135. : Which logic gate produces a HIGH output only when all its inputs are HIGH? — From PPSC Sub Engineer (Electrical) Exam, 2020
(A) OR Gate
(B) NOR Gate
(C) AND Gate
(D) NAND Gate
136. : The binary equivalent of decimal number 25 is: — From WAPDA Technical Cadre Test, 2018
(A) 11001
(B) 10101
(C) 11010
(D) 11100
137. : Which number system uses base 16? — From Junior Engineer (Electrical) PPSC Test, 2021
(A) Binary
(B) Decimal
(C) Octal
(D) Hexadecimal
138. : In digital logic, a flip-flop is used for: — From WAPDA Power Division Screening Test, 2019
(A) Logic multiplication
(B) Data storage
(C) Signal addition
(D) Amplification
139. : The main function of an ALU (Arithmetic Logic Unit) in a microprocessor is: — From FPSC Assistant Engineer (Electrical) Exam, 2020
(A) To store instructions
(B) To perform arithmetic and logic operations
(C) To control input-output devices
(D) To fetch data from memory
140. : Which of the following memories is non-volatile? — From PPSC Electrical Supervisor Test, 2021
(A) RAM
(B) Cache
(C) ROM
(D) Register
141. : The smallest unit of data in a computer system is: — From WAPDA Engineering Services Test, 2019
(A) Bit
(B) Byte
(C) Word
(D) Nibble
142. : Which logic gate is known as a universal gate? — From PPSC Sub Engineer (Electrical) Paper, 2022
(A) AND Gate
(B) OR Gate
(C) NAND Gate
(D) XOR Gate
143. : The hexadecimal number “A2” is equivalent to decimal: — From WAPDA Electrical Engineer Test, 2020
(A) 152
(B) 162
(C) 172
(D) 142
144. : Which component is used to convert analog signal into digital signal? — From PPSC Junior Engineer Test, 2018
(A) DAC
(B) ADC
(C) Amplifier
(D) Comparator
145. : The microprocessor 8085 has how many address lines? — From FPSC Electrical Engineer Exam, 2019
(A) 8
(B) 12
(C) 16
(D) 20
146. : The instruction cycle of a microprocessor consists of: — From WAPDA Technical Post Exam, 2021
(A) Fetch and Execute
(B) Decode and Store
(C) Read and Write
(D) Input and Output
147. : The Boolean expression A + A’B simplifies to: — From PPSC Electrical Sub Engineer Test, 2020
(A) A
(B) A + B
(C) A’B
(D) B
148. : A half adder has: — From WAPDA Electrical Engineer Exam, 2017
(A) 1 input, 1 output
(B) 2 inputs, 2 outputs
(C) 3 inputs, 1 output
(D) 2 inputs, 1 output
149. : In digital electronics, 1 Kbyte equals: — From PPSC Assistant Engineer Exam, 2022
(A) 1000 bytes
(B) 1024 bytes
(C) 2048 bytes
(D) 512 bytes
150. : The CPU of a computer primarily performs: — From WAPDA Power Systems Test, 2021
(A) Computation and control functions
(B) Memory operations only
(C) Display functions
(D) Input functions
151. : The device that converts electrical energy into light energy is: — From PPSC Electrical Supervisor Exam, 2020
(A) Heater
(B) Lamp
(C) Transformer
(D) Inductor
152. : Electric traction refers to: — From WAPDA Transport & Power Utilization Exam, 2018
(A) Electrical train movement
(B) Lifting heavy loads
(C) Pumping stations
(D) Power factor correction
153. : The main advantage of electric traction over steam traction is: — From PPSC Electrical Engineer Test, 2021
(A) Less maintenance and higher efficiency
(B) High smoke generation
(C) Slower speed
(D) High noise level
154. : The power factor of an electric traction system is usually: — From WAPDA Technical Post Exam, 2019
(A) Unity
(B) Lagging
(C) Leading
(D) Zero
155. : The main fuel used in thermal power plants is: — From WAPDA Junior Engineer (Electrical) Exam, 2019
(A) Coal
(B) Diesel
(C) Gas
(D) All of these
156. : The alternator in a power plant converts: — From PPSC Sub Engineer (Electrical) Exam, 2020
(A) Mechanical energy into electrical energy
(B) Electrical energy into mechanical energy
(C) Chemical energy into electrical energy
(D) Thermal energy into mechanical energy
157. : The frequency of electrical power generated in Pakistan is: — From WAPDA Technical Services Test, 2021
(A) 25 Hz
(B) 50 Hz
(C) 60 Hz
(D) 75 Hz
158. : The part of the thermal power station that converts water into steam is called: — From PPSC Assistant Engineer (Electrical) Exam, 2022
(A) Boiler
(B) Condenser
(C) Turbine
(D) Economizer
159. : The power factor of a purely inductive circuit is: — From FPSC Electrical Engineer Exam, 2020
(A) Unity
(B) Zero lagging
(C) Zero leading
(D) 0.5 lagging
160. : The function of the turbine in a power plant is to: — From WAPDA Generation Division Test, 2019
(A) Generate electricity directly
(B) Convert steam energy into mechanical energy
(C) Condense steam
(D) Pump water
161. : The transmission voltage in Pakistan is generally: — From PPSC Electrical Sub Engineer Test, 2021
(A) 230 V
(B) 11 kV
(C) 132 kV
(D) 440 V
162. : Grid frequency is maintained constant by: — From WAPDA Power System Operation Exam, 2020
(A) Automatic voltage regulator
(B) Speed governor on turbines
(C) Circuit breakers
(D) Transformers
163. : The most efficient method of power transmission is: — From PPSC Junior Engineer (Electrical) Paper, 2018
(A) Low-voltage DC
(B) High-voltage AC
(C) Low-voltage AC
(D) High-current DC
164. : Corona effect occurs on: — From WAPDA Technical Cadre Exam, 2019
(A) Underground cables
(B) Transformer windings
(C) Overhead transmission lines at high voltage
(D) DC circuits
165. : The insulators used in transmission lines are made of: — From PPSC Electrical Engineer Exam, 2020
(A) Copper
(B) Porcelain
(C) Aluminum
(D) Steel
166. : The power loss in a transmission line is proportional to: — From WAPDA Power Division Test, 2018
(A) I
(B) I²
(C) V
(D) V²
167. : Transmission efficiency increases with: — From PPSC Sub Engineer (Electrical) Exam, 2022
(A) Low voltage
(B) High voltage
(C) High current
(D) Low power factor
168. : In hydroelectric power stations, the turbine is driven by: — From WAPDA Hydel Power Wing Exam, 2021
(A) Steam
(B) Gas
(C) Water
(D) Wind
169. : 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
170. : 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
171. : 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
172. : 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
173. : 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
174. : 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)
175. : 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
176. : 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
177. : Which component steps up the voltage in a power station? — From PPSC Power Distribution Exam, 2020
(A) Transformer
(B) Inductor
(C) Alternator
(D) Motor
178. : 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
179. : 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
180. : 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
181. : 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
182. : 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
183. : 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
184. : 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
185. : 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
186. : A fuse is used for: — From WAPDA Technical Services Test, 2019
(A) Voltage regulation
(B) Overcurrent protection
(C) Frequency control
(D) Power factor correction
187. : 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
188. : 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
189. : 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
190. : 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
191. : 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
192. : 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
193. : 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
194. : 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
195. : 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
196. : 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
197. : 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
198. : 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
199. : 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
200. : 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
201. : 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
202. : 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
203. : 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
204. : 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
205. : 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
206. : The power factor of an inductive circuit is: — from PPSC Sub Engineer Electrical 2019
(A) Leading
(B) Lagging
(C) Unity
(D) Zero
207. : The unit of magnetic flux density is: — from NTDC Engineer Electrical Test 2020
(A) Henry
(B) Weber
(C) Tesla
(D) Ohm
208. : 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
209. : 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
210. : 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
211. : 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
212. : 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
213. : 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
214. : The insulation resistance of a good conductor is: — from MEPCO Technical Cadre Test 2021
(A) Very high
(B) Very low
(C) Zero
(D) Infinite
215. : 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
216. : 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
217. : 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
218. : 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
219. : The core of a power transformer is made of: — from PPSC Sub Engineer (Electrical) 2017
(A) Copper
(B) Aluminum
(C) Silicon steel
(D) Zinc
220. : 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
221. : 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%
222. : 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
223. : 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
224. : 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
225. : 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
226. : 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
227. : 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
228. : The power factor in a purely inductive circuit is: — from PPSC Electrical Inspector 2018
(A) Zero
(B) Unity
(C) Lagging
(D) Leading
229. : 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
230. : 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°
231. : A Buchholz relay is used for the protection of: — from PPSC Electrical Engineer 2019
(A) Transmission lines
(B) Induction motors
(C) Transformers
(D) Alternators
232. : 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
233. : 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
234. : 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
235. : 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
236. : 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
237. : 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
238. : 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
239. : 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
240. : 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
241. : Which device automatically isolates a circuit during fault conditions? — from PESCO Electrical Supervisor 2021
(A) Fuse
(B) Relay
(C) Circuit breaker
(D) Isolator
242. : 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
243. : 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
244. : 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
245. : The main component of thermal power plant is: — from WAPDA Electrical Engineer Exam 2019
(A) Boiler
(B) Cooling tower
(C) Condenser
(D) Alternator
246. : 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
247. : 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%
248. : 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
249. : 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
250. : 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
251. : 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°
252. : 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
253. : 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
254. : The efficiency of a transformer is maximum when: — from PPSC Electrical Inspector Test 2020
(A) Iron losses = Copper losses
Copper losses” onclick=”checkAnswer(‘q254’, ‘Iron losses = Copper losses’)”> (B) Iron losses > Copper losses
(C) Iron losses < Copper losses
(D) Load is full
255. : 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
256. : 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
257. : 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
258. : 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
259. : 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
260. : The voltage regulation of an ideal transformer is: — from FESCO Junior Engineer Test 2020
(A) 0%
(B) 50%
(C) 100%
(D) 10%
261. : 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
262. : The efficiency of a DC motor is maximum when: — from WAPDA Junior Engineer 2020
(A) Copper losses = Constant losses
Iron losses” onclick=”checkAnswer(‘q262’, ‘Copper losses = Constant losses’)”> (B) Copper losses > Iron losses
(C) Copper losses < Iron losses
(D) None of these
263. : 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
264. : 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
265. : The instrument used for measuring electric potential difference is: — from PPSC Sub Engineer (Electrical) 2021
(A) Voltmeter
(B) Ammeter
(C) Wattmeter
(D) Ohmmeter
266. : 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
267. : Which instrument measures the power in an AC circuit? — from MEPCO Assistant Engineer Electrical 2021
(A) Ammeter
(B) Voltmeter
(C) Wattmeter
(D) Energy meter
268. : 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
269. : 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
270. : 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
271. : 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
272. : 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
273. : The instrument used to measure insulation resistance is: — from MEPCO Sub Engineer Electrical 2022
(A) Voltmeter
(B) Ammeter
(C) Megger
(D) Multimeter
274. : 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
275. : 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
276. : 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
277. : 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
278. : 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
279. : The unit of capacitance is: — from PPSC Electrical Sub Engineer Exam 2021
(A) Ohm
(B) Farad
(C) Henry
(D) Volt
280. : 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
281. : The principle of operation of LVDT is based on: — from PPSC Instrumentation Engineer 2020
(A) Capacitance
(B) Inductance
(C) Resistance
(D) Magnetic field
282. : 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
283. : Tachometer is used to measure: — from MEPCO Electrical Engineer Exam 2021
(A) Voltage
(B) Speed
(C) Torque
(D) Temperature
284. : 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
285. : 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
286. : 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
287. : 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
288. : 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
289. : 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
290. : 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)
291. : 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
292. : 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
293. : 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
294. : 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
295. : 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
296. : 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
297. : 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
298. : 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
299. : 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
300. : The power factor of an inductive load is usually? (PPSC Electrical Sub Engineer – 2020)
(A) Leading
(B) Lagging
(C) Unity
(D) Zero
301. : 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
302. : Which instrument is used to measure insulation resistance? (PPSC Assistant Engineer Electrical – 2022)
(A) Megger
(B) Voltmeter
(C) Wattmeter
(D) Multimeter
303. : 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
304. : 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
305. : 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
306. : 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
307. : 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
308. : 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
309. : 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
310. : 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
311. : 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
312. : 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
313. : 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
314. : 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
315. : 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
316. : 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
317. : 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
318. : 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
319. : 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
320. : 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
321. : 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
322. : 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
323. : 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
324. : 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
325. : What is the purpose of using a breather in a transformer? (NTDC Electrical Engineer – 2022)
(A) To remove moisture from the air entering the conservator tank
(B) To increase cooling efficiency
(C) To filter transformer oil
(D) To detect internal faults
326. : Which part of the transformer is laminated to reduce eddy current losses? (PPSC Assistant Engineer Electrical – 2021)
(A) Windings
(B) Core
(C) Tank
(D) Bushings
327. : The primary function of a transformer is to? (WAPDA Electrical Engineer – 2020)
(A) Convert AC to DC
(B) Step up or step down voltage
(C) Store electrical energy
(D) Measure current
328. : In a transformer, the no-load current is approximately what percentage of the full-load current? (NTDC Electrical Engineer – 2023)
(A) 1–2%
(B) 5–10%
(C) 20–25%
(D) 30–35%
329. : Which test is conducted on a transformer to determine copper losses? (PPSC Electrical Engineer – 2021)
(A) Open-circuit test
(B) Short-circuit test
(C) Insulation test
(D) Polarity test
330. : Which type of cooling is used in large power transformers? (LESCO Engineer Recruitment Test – 2022)
(A) Air natural
(B) Oil natural air natural (ONAN)
(C) Air blast
(D) Water cooling
331. : What is the function of a tap changer in a transformer? (PESCO Electrical Engineer – 2021)
(A) To change the turns ratio for voltage regulation
(B) To increase efficiency
(C) To change frequency
(D) To control temperature
332. : The instrument used to measure insulation resistance is? (WAPDA Electrical Engineer – 2019)
(A) Wattmeter
(B) Voltmeter
(C) Megger
(D) Multimeter
333. : Which of the following is NOT a type of transformer loss? (NTDC Electrical Engineer – 2023)
(A) Core loss
(B) Copper loss
(C) Friction loss
(D) Eddy current loss
334. : The efficiency of a transformer is maximum when? (PPSC Electrical Engineer – 2020)
(A) Iron losses = Copper losses
(B) Iron losses < Copper losses
Copper losses” onclick=”checkAnswer(‘q334’, ‘Iron losses = Copper losses’)”> (C) Iron losses > Copper losses
(D) Iron losses are zero
335. : The main reason for transformer humming noise is? (NTDC Electrical Engineer – 2023)
(A) Vibration of windings due to magnetostriction in the core
(B) Loose joints in the tank
(C) Oil circulation
(D) Air bubbles in winding insulation
336. : What is the typical value of transformer oil temperature rise over ambient temperature? (PPSC Electrical Engineer – 2021)
(A) 10–20°C
(B) 30–40°C
(C) 45–55°C
(D) 60–70°C
337. : In a power transformer, the leakage flux is minimized by? (WAPDA Electrical Engineer – 2020)
(A) Using laminated core
(B) Using concentric windings
(C) Increasing air gap
(D) Using higher resistance conductors
338. : What is the purpose of a conservator tank in an oil-filled transformer? (LESCO Engineer Recruitment Test – 2021)
(A) To provide space for oil expansion and contraction
(B) To store excess oil permanently
(C) To cool the transformer core
(D) To collect impurities
339. : What is the approximate efficiency of a large power transformer at full load? (PESCO Electrical Engineer – 2020)
(A) 50%
(B) 70%
(C) 90%
(D) 98%
340. : Which device is used to measure the oil level in a transformer conservator? (NTDC Electrical Engineer – 2022)
(A) Thermometer
(B) Hydrometer
(C) Magnetic oil gauge
(D) Pressure gauge
341. : The insulation resistance of a transformer should be tested with? (PPSC Assistant Engineer Electrical – 2021)
(A) Multimeter
(B) Megger
(C) Earth tester
(D) Ohmmeter
342. : The main cause of transformer efficiency reduction is? (WAPDA Electrical Engineer – 2021)
(A) Core losses
(B) Copper losses
(C) Leakage reactance
(D) Both (A) and (B)
343. : What type of transformer is used for electrical isolation without voltage change? (NTDC Electrical Engineer – 2023)
(A) Step-up transformer
(B) Step-down transformer
(C) Isolation transformer
(D) Auto-transformer
344. : The main advantage of an auto-transformer over a two-winding transformer is? (PPSC Electrical Engineer – 2021)
(A) Higher losses
(B) Larger size
(C) Higher efficiency and smaller size
(D) Lower voltage regulation
345. : The frequency of an alternator depends on? (PPSC Electrical Engineer – 2021)
(A) Speed of rotor only
(B) Number of poles only
(C) Both speed and number of poles
(D) Type of stator winding
346. : In an alternator, the generated EMF is directly proportional to? (WAPDA Electrical Engineer – 2020)
(A) Speed
(B) Flux per pole
(C) Number of turns
(D) All of the above
347. : The rotating part of an alternator is known as? (NTDC Electrical Engineer – 2022)
(A) Stator
(B) Rotor
(C) Armature
(D) Commutator
348. : What happens if the field current of a synchronous motor is increased beyond the normal value? (PESCO Electrical Engineer – 2021)
(A) Power factor decreases
(B) Power factor becomes lagging
(C) Power factor becomes leading
(D) Motor speed increases
349. : The armature winding of an alternator is usually placed on? (LESCO Assistant Engineer – 2022)
(A) Rotor
(B) Stator
(C) Shaft
(D) Slip rings
350. : The main purpose of damper windings in a synchronous motor is to? (NTDC Electrical Engineer – 2023)
(A) Reduce noise
(B) Prevent hunting
(C) Increase efficiency
(D) Reduce armature reaction
351. : The emf generated per phase in an alternator is given by? (PPSC Sub Engineer Electrical – 2020)
(A) 2.22 f N Φ
(B) 4.44 f N Φ
(C) 2 f N Φ
(D) 1.11 f N Φ
352. : When a synchronous motor runs at no load and unity power factor, its armature current is? (WAPDA Electrical Engineer – 2021)
(A) Minimum
(B) Maximum
(C) Zero
(D) Constant
353. : The voltage regulation of an alternator is negative when the load power factor is? (LESCO Electrical Engineer – 2020)
(A) Lagging
(B) Unity
(C) Leading
(D) Zero
354. : Which method is commonly used to determine voltage regulation of an alternator? (PPSC Electrical Engineer – 2022)
(A) Short-circuit test
(B) Open-circuit test
(C) Synchronous impedance method
(D) Slip test
355. : In a three-phase induction motor, the rotating magnetic field rotates at? (PPSC Electrical Engineer – 2021)
(A) Synchronous speed
(B) Rotor speed
(C) Slip speed
(D) Half synchronous speed
356. : The starting torque of a squirrel cage induction motor is generally? (WAPDA Electrical Engineer – 2020)
(A) Low
(B) High
(C) Infinite
(D) Same as full-load torque
357. : The slip at full load in an induction motor is typically about? (LESCO Sub Engineer Electrical – 2021)
(A) 0.1%
(B) 1%–3%
(C) 5%–8%
(D) 10%–15%
358. : Which method is used to control the speed of an induction motor above its synchronous speed? (PESCO Electrical Engineer – 2022)
(A) Rotor resistance control
(B) Stator voltage control
(C) Cascade connection
(D) None, it cannot be operated above synchronous speed
359. : In a 3-phase induction motor, the torque is maximum when? (PPSC Electrical Engineer – 2021)
(A) Rotor resistance equals rotor reactance
(B) Rotor reactance is zero
(C) Slip is zero
(D) Supply frequency is maximum
360. : The starting torque of a DC series motor is? (WAPDA Electrical Engineer – 2020)
(A) Low
(B) Medium
(C) High
(D) Zero
361. : The direction of rotation of a DC motor can be reversed by? (NTDC Electrical Engineer – 2023)
(A) Reversing field connections only
(B) Reversing armature connections only
(C) Reversing either field or armature connections
(D) Reversing both field and armature connections simultaneously
362. : In a DC generator, the function of the commutator is to? (PPSC Sub Engineer Electrical – 2020)
(A) Convert AC to DC
(B) Convert DC to AC
(C) Reduce losses
(D) Increase efficiency
363. : The speed of a DC shunt motor is almost constant because? (LESCO Electrical Engineer – 2021)
(A) Flux is proportional to armature current
(B) Flux remains practically constant
(C) Armature resistance is very high
(D) Field current varies with load
364. : The back EMF in a DC motor is proportional to? (WAPDA Electrical Engineer – 2022)
(A) Armature current
(B) Field current
(C) Speed and flux
(D) Load torque
365. : The primary source of energy in a thermal power plant is? (PPSC Electrical Engineer – 2021)
(A) Coal
(B) Diesel
(C) Natural Gas
(D) All of these
366. : The efficiency of a thermal power plant is usually in the range of? (WAPDA Electrical Engineer – 2020)
(A) 15–25%
(B) 25–35%
(C) 35–45%
(D) 45–60%
367. : In a hydroelectric power plant, the energy of water is converted into? (PPSC Assistant Engineer Electrical – 2022)
(A) Mechanical energy by turbine
(B) Heat energy
(C) Chemical energy
(D) Electrical energy directly
368. : The capacity of a generator in a power station is usually expressed in? (NTDC Electrical Engineer – 2023)
(A) kW
(B) MW
(C) MVA
(D) kVA
369. : The ideal power factor for maximum efficiency in power transmission is? (LESCO Electrical Engineer – 2021)
(A) 0.5
(B) 0.707
(C) 1.0
(D) 0.9
370. : The load factor of a power plant is defined as? (WAPDA Electrical Engineer – 2022)
(A) Ratio of average load to maximum demand
(B) Ratio of maximum demand to average load
(C) Ratio of plant capacity to load factor
(D) Ratio of connected load to maximum demand
371. : Which generator is used in a hydroelectric power station? (PPSC Electrical Engineer – 2020)
(A) DC generator
(B) Synchronous generator
(C) Induction generator
(D) Variable frequency generator
372. : The transmission efficiency increases when? (NTDC Electrical Engineer – 2023)
(A) Line voltage is increased
(B) Line current is increased
(C) Power factor is reduced
(D) Line losses are increased
373. : In power systems, corona loss increases with? (LESCO Electrical Engineer – 2022)
(A) Decrease in voltage
(B) Increase in frequency
(C) Decrease in conductor size
(D) Increase in conductor spacing
374. : The sag in an overhead transmission line increases when? (PESCO Electrical Engineer – 2021)
(A) Tension is increased
(B) Temperature increases
(C) Weight of conductor decreases
(D) Span is reduced
375. : The main function of protective relays in a power system is to? (PPSC Electrical Engineer – 2021)
(A) Protect equipment from overloading
(B) Detect faults and isolate faulty sections
(C) Control system voltage
(D) Maintain frequency
376. : A Buchholz relay is used for the protection of? (WAPDA Electrical Engineer – 2020)
(A) Transmission line
(B) Transformer
(C) Alternator
(D) Induction motor
377. : An overcurrent relay operates when? (NTDC Electrical Engineer – 2022)
(A) The current exceeds a preset value
(B) Voltage falls below rated value
(C) Frequency increases
(D) Power factor decreases
378. : Differential protection is based on the principle of? (LESCO Electrical Engineer – 2021)
(A) Comparing currents at two ends of equipment
(B) Comparing voltages across a line
(C) Measuring reactive power
(D) Detecting frequency change
379. : A lightning arrester is connected between? (PESCO Electrical Engineer – 2022)
(A) Phase and neutral
(B) Phase and ground
(C) Phase and phase
(D) Neutral and earth
380. : The primary purpose of a circuit breaker is to? (PPSC Assistant Engineer Electrical – 2020)
(A) Control reactive power
(B) Interrupt short-circuit currents
(C) Step down voltage
(D) Measure current
381. : Which of the following circuit breakers uses compressed air for arc extinction? (NTDC Electrical Engineer – 2023)
(A) Air-blast circuit breaker
(B) Vacuum circuit breaker
(C) Oil circuit breaker
(D) SF₆ circuit breaker
382. : The arc in a circuit breaker is extinguished by? (WAPDA Electrical Engineer – 2021)
(A) Cooling and lengthening of arc
(B) Increasing resistance of arc path
(C) Separation of contacts
(D) All of these
383. : SF₆ circuit breakers are preferred for high voltage applications because SF₆ gas has? (LESCO Electrical Engineer – 2022)
(A) High thermal conductivity
(B) Excellent dielectric strength
(C) Arc-quenching properties
(D) All of these
384. : In a power system, the relay operates but circuit breaker fails to trip — this condition is known as? (PPSC Electrical Engineer – 2021)
(A) Back feeding
(B) Breaker failure
(C) Overreach
(D) Underreach
385. : In a DC shunt motor, if the field winding is opened while the motor is running, the motor will: (NTDC Electrical Engineer – 2023)
(A) Stop immediately
(B) Run at dangerously high speed
(C) Run at reduced speed
(D) Burn due to short circuit
386. : The open-circuit test on a transformer primarily measures: (PESCO Electrical Engineer – 2022)
(A) Copper losses
(B) Iron losses
(C) Efficiency
(D) Regulation
387. : The short-circuit test on a transformer is conducted to determine: (WAPDA Electrical Engineer – 2021)
(A) Iron losses
(B) Efficiency
(C) Copper losses
(D) Voltage regulation
388. : The core of a transformer is laminated to reduce: (NTDC Electrical Engineer – 2023)
(A) Hysteresis losses
(B) Eddy current losses
(C) Copper losses
(D) Magnetic flux
389. : The voltage regulation of a transformer is maximum at: (FESCO Electrical Engineer – 2022)
(A) Unity power factor
(B) Lagging power factor
(C) Leading power factor
(D) Zero power factor
390. : The primary and secondary windings of a transformer are: (NTDC Electrical Engineer – 2021)
(A) Conductively coupled
(B) Magnetically coupled
(C) Inductively isolated
(D) Electrically connected
391. : The efficiency of a transformer is maximum when: (PESCO Electrical Engineer – 2023)
(A) Copper losses are minimum
(B) Iron losses are minimum
(C) Copper losses = Iron losses
(D) Load is full
392. : Which of the following motors is best suited for constant speed applications? (LESCO Electrical Engineer – 2022)
(A) DC shunt motor
(B) DC series motor
(C) Universal motor
(D) Stepper motor
393. : The speed of a DC shunt motor can be controlled by varying: (NTDC Electrical Engineer – 2023)
(A) Supply voltage
(B) Armature resistance
(C) Field current
(D) Any of the above
394. : The back emf in a DC motor is directly proportional to: (PESCO Electrical Engineer – 2022)
(A) Armature current
(B) Speed of the motor
(C) Supply voltage
(D) Torque
395. : In a DC generator, the purpose of the commutator is to: (PPSC Electrical Engineer – 2021)
(A) Convert AC to DC
(B) Convert DC to AC
(C) Reduce armature reaction
(D) Provide mechanical support
396. : In a DC motor, torque is directly proportional to: (WAPDA Electrical Engineer – 2020)
(A) Armature voltage only
(B) Flux and armature current
(C) Speed and flux
(D) Resistance and current
397. : What is the function of a starter in a DC motor? (LESCO Electrical Engineer – 2021)
(A) To increase speed
(B) To limit starting current
(C) To reduce torque
(D) To control temperature
398. : The main cause of sparking at brushes in a DC machine is: (PESCO Electrical Engineer – 2022)
(A) High armature current
(B) Poor commutation
(C) High speed
(D) Field weakening
399. : The armature reaction in a DC generator causes: (PPSC Sub Engineer Electrical – 2022)
(A) Increase in terminal voltage
(B) Distortion of main flux
(C) Increase in armature resistance
(D) Decrease in speed
400. : The efficiency of a DC generator is maximum when: (WAPDA Electrical Engineer – 2019)
(A) Iron losses = Copper losses
(B) Load current is maximum
(C) Copper losses = Stray losses
(D) Mechanical losses = Electrical losses
401. : In a DC motor, back EMF is produced because of: (NTDC Electrical Engineer – 2023)
(A) Lenz’s Law
(B) Faraday’s Law of Electromagnetic Induction
(C) Fleming’s Left-Hand Rule
(D) Joule’s Law
402. : The speed of a DC shunt motor can be controlled by varying: (PPSC Assistant Engineer Electrical – 2021)
(A) Supply voltage
(B) Field current
(C) Load torque
(D) Armature resistance only
403. : In a DC series motor, the speed is inversely proportional to: (WAPDA Sub Engineer Electrical – 2020)
(A) Armature voltage
(B) Armature current
(C) Field flux
(D) Supply voltage
404. : The function of interpoles in a DC machine is to: (PESCO Electrical Engineer – 2022)
(A) Reduce armature reaction
(B) Improve commutation
(C) Increase speed
(D) Reduce losses
405. : The main purpose of using a transformer is to: (PPSC Electrical Engineer – 2021)
(A) Convert AC to DC
(B) Step up or step down AC voltage
(C) Increase frequency
(D) Decrease current losses only
406. : The core of a transformer is laminated to: (WAPDA Electrical Engineer – 2020)
(A) Reduce copper losses
(B) Reduce eddy current losses
(C) Increase efficiency
(D) Reduce hysteresis losses
407. : In a transformer, the voltage per turn is: (LESCO Electrical Engineer – 2021)
(A) Same for both primary and secondary windings
(B) Different for primary and secondary windings
(C) Greater in primary winding
(D) Greater in secondary winding
408. : Which type of transformer is used for measuring high voltages? (NTDC Electrical Engineer – 2023)
(A) Potential transformer
(B) Power transformer
(C) Distribution transformer
(D) Isolation transformer
409. : The efficiency of a transformer is maximum when: (PESCO Sub Engineer Electrical – 2022)
(A) Iron losses = Copper losses
(B) Copper losses are minimum
(C) Load is full
(D) Iron losses are zero
410. : What is the purpose of oil in a transformer? (WAPDA Electrical Engineer – 2019)
(A) Cooling and insulation
(B) Power factor correction
(C) Voltage regulation
(D) Current control
411. : The open-circuit test on a transformer gives: (PPSC Electrical Engineer – 2021)
(A) Copper losses
(B) Iron losses
(C) Efficiency
(D) Voltage regulation
412. : The short-circuit test on a transformer gives: (NTDC Electrical Engineer – 2022)
(A) Iron losses
(B) Hysteresis losses
(C) Copper losses
(D) Dielectric losses
413. : The auto-transformer is more efficient because: (LESCO Engineer Recruitment Test – 2021)
(A) It has one winding partly common to both primary and secondary
(B) It has more copper loss
(C) It has more leakage reactance
(D) It uses less magnetic material
414. : Which of the following is not a type of transformer loss? (PESCO Electrical Engineer – 2023)
(A) Copper loss
(B) Iron loss
(C) Stray loss
(D) Corona loss
415. : In an induction motor, the speed of the rotor is always: (PPSC Electrical Engineer – 2021)
(A) Equal to synchronous speed
(B) Less than synchronous speed
(C) Greater than synchronous speed
(D) Zero
416. : The rotating magnetic field in a 3-phase induction motor rotates at: (NTDC Electrical Engineer – 2023)
(A) Rotor speed
(B) Synchronous speed
(C) Slip speed
(D) Zero speed
417. : The slip in an induction motor is given by: (WAPDA Electrical Engineer – 2020)
(A) (Ns – Nr) / Ns
(B) (Nr – Ns) / Nr
(C) Ns / Nr
(D) Nr / Ns
418. : The torque developed by an induction motor is maximum when: (LESCO Engineer Recruitment Test – 2022)
(A) Rotor resistance = Rotor reactance
(B) Rotor resistance < Rotor reactance
Rotor reactance” onclick=”checkAnswer(‘q418’, ‘Rotor resistance = Rotor reactance’)”> (C) Rotor resistance > Rotor reactance
(D) Slip = 0
419. : The starting torque of a squirrel cage induction motor is: (PESCO Electrical Engineer – 2021)
(A) Very high
(B) Moderate
(C) Very low
(D) Infinite
420. : Which method is commonly used to start a three-phase induction motor? (PPSC Sub Engineer Electrical – 2022)
(A) Direct-on-line starter
(B) Resistance starter
(C) Inductive starter
(D) Rotor start method
421. : In a synchronous motor, the rotor speed is: (NTDC Electrical Engineer – 2023)
(A) Equal to synchronous speed
(B) Less than synchronous speed
(C) Greater than synchronous speed
(D) Independent of frequency
422. : The excitation of a synchronous motor is provided by: (WAPDA Electrical Engineer – 2020)
(A) Induction effect
(B) DC source
(C) Alternating current
(D) Capacitor
423. : The main advantage of a synchronous motor over an induction motor is: (LESCO Sub Engineer Electrical – 2022)
(A) It is cheaper
(B) It can operate at unity power factor
(C) It requires no excitation
(D) It has higher slip
424. : If the load on a synchronous motor increases, the motor’s: (PPSC Electrical Engineer – 2021)
(A) Speed increases
(B) Speed decreases
(C) Power factor changes
(D) Frequency increases
425. : Power factor of an AC circuit is defined as: (PPSC Electrical Engineer – 2021)
(A) Ratio of active power to apparent power
(B) Ratio of reactive power to active power
(C) Ratio of voltage to current
(D) Ratio of apparent power to active power
426. : A lagging power factor is caused by: (WAPDA Electrical Engineer – 2020)
(A) Capacitive load
(B) Inductive load
(C) Resistive load
(D) Short circuit
427. : The main purpose of power factor correction is to: (NTDC Electrical Engineer – 2023)
(A) Reduce voltage
(B) Reduce current and losses
(C) Increase frequency
(D) Reduce power
428. : Synchronous capacitors are used in power systems to: (LESCO Electrical Engineer – 2022)
(A) Supply reactive power and improve power factor
(B) Reduce voltage
(C) Increase frequency
(D) Reduce harmonics
429. : An alternator converts: (PESCO Electrical Engineer – 2021)
(A) Mechanical energy into DC electrical energy
(B) Mechanical energy into AC electrical energy
(C) Electrical energy into mechanical energy
(D) Heat energy into electrical energy
430. : The synchronous speed of a 6-pole alternator operating at 50 Hz is: (PPSC Sub Engineer Electrical – 2022)
(A) 1000 rpm
(B) 500 rpm
(C) 1500 rpm
(D) 3000 rpm
431. : The voltage induced in an alternator is proportional to: (NTDC Electrical Engineer – 2023)
(A) Speed and flux per pole
(B) Load current only
(C) Frequency only
(D) Armature resistance
432. : In an alternator, the efficiency is maximum when: (WAPDA Electrical Engineer – 2020)
(A) Load is zero
(B) Copper losses = Iron losses
Iron losses” onclick=”checkAnswer(‘q432’, ‘Copper losses = Iron losses’)”> (C) Copper losses > Iron losses
(D) Iron losses = 0
433. : The voltage regulation of an alternator is: (LESCO Sub Engineer Electrical – 2022)
(A) Ratio of no-load voltage to full-load voltage
(B) Ratio of full-load voltage to no-load voltage
(C) Change in voltage from no-load to full-load at constant speed
(D) Ratio of reactive power to active power
434. : Which of the following affects the voltage regulation of an alternator? (PESCO Electrical Engineer – 2021)
(A) Load power factor
(B) Excitation
(C) Internal impedance
(D) All of these
435. : The efficiency of a transformer depends mainly on: (NTDC Electrical Engineer – 2023)
(A) Load and copper losses
(B) Core material only
(C) Frequency only
(D) Voltage regulation
436. : In a 3-phase induction motor, the direction of rotation can be reversed by: (PESCO Electrical Engineer – 2022)
(A) Swapping any two phases of supply
(B) Changing the rotor resistance
(C) Increasing the supply voltage
(D) Changing the frequency
437. : The rotor of a squirrel cage induction motor has: (LESCO Electrical Engineer – 2021)
(A) Wound rotor with slip rings
(B) Laminated rotor with bars short-circuited at ends
(C) Solid copper rotor
(D) Ferrite core rotor
438. : The synchronous speed of a 4-pole, 50 Hz induction motor is: (PPSC Electrical Engineer – 2021)
(A) 1000 rpm
(B) 1500 rpm
(C) 1200 rpm
(D) 1800 rpm
439. : The primary purpose of a protective relay in a power system is to: (WAPDA Electrical Engineer – 2020)
(A) Measure current
(B) Detect faults and initiate circuit breaker operation
(C) Regulate voltage
(D) Control frequency
440. : A Buchholz relay is primarily used in: (NTDC Electrical Engineer – 2023)
(A) Transmission lines
(B) Transformers
(C) Generators
(D) Synchronous motors
441. : The slip of an induction motor is zero when: (PESCO Electrical Engineer – 2022)
(A) Motor is running at synchronous speed
(B) Motor is at start
(C) Motor is at half load
(D) Rotor is stationary
442. : In a DC shunt motor, the speed decreases with: (LESCO Electrical Engineer – 2021)
(A) Increase in load
(B) Decrease in load
(C) Increase in supply voltage
(D) Decrease in armature resistance
443. : The main advantage of a synchronous motor is: (PPSC Electrical Engineer – 2021)
(A) Constant speed operation
(B) High starting torque
(C) Simple starting method
(D) Self-excitation
444. : In power factor correction, capacitors are used to: (WAPDA Electrical Engineer – 2020)
(A) Improve power factor
(B) Reduce active power
(C) Reduce frequency
(D) Increase line losses
445. : The main cause of low power factor in an industrial AC circuit is: (PESCO Electrical Engineer – 2022)
(A) Resistive load
(B) Inductive load
(C) Capacitive load
(D) High voltage
446. : Synchronous capacitors are primarily used to: (NTDC Electrical Engineer – 2023)
(A) Supply reactive power and improve power factor
(B) Reduce active power
(C) Increase frequency
(D) Reduce harmonics
447. : The voltage regulation of a transformer depends mainly on: (WAPDA Electrical Engineer – 2020)
(A) Load current and power factor
(B) Frequency only
(C) Core material
(D) Cooling method
448. : The efficiency of a transformer is maximum when: (LESCO Electrical Engineer – 2021)
(A) Copper losses = Iron losses
Iron losses” onclick=”checkAnswer(‘q448’, ‘Copper losses = Iron losses’)”> (B) Copper losses > Iron losses
(C) Iron losses = 0
(D) Load is zero
449. : The primary and secondary windings of a transformer are: (PPSC Electrical Engineer – 2021)
(A) Electrically connected
(B) Magnetically coupled
(C) Short-circuited
(D) Isolated with no magnetic coupling
450. : A step-up transformer increases: (NTDC Electrical Engineer – 2023)
(A) Current
(B) Voltage
(C) Frequency
(D) Resistance
451. : The main purpose of using a starter in a DC motor is to: (PESCO Electrical Engineer – 2022)
(A) Limit starting current
(B) Increase speed
(C) Reduce torque
(D) Control temperature
452. : In a DC series motor, the speed is inversely proportional to: (LESCO Electrical Engineer – 2021)
(A) Armature current
(B) Field flux
(C) Supply voltage
(D) Load torque
453. : The back EMF in a DC motor is proportional to: (PPSC Electrical Engineer – 2021)
(A) Armature current
(B) Speed of the motor
(C) Supply voltage
(D) Torque
454. : The main function of a Buchholz relay is to: (WAPDA Electrical Engineer – 2020)
(A) Detect overheating in alternator
(B) Detect internal faults in transformers
(C) Measure power factor
(D) Protect induction motor
455. : The primary winding of a transformer is connected to: (NTDC Electrical Engineer – 2023)
(A) AC supply
(B) DC supply
(C) Load
(D) Ground
456. : The secondary winding of a transformer delivers: (PESCO Electrical Engineer – 2022)
(A) AC voltage
(B) DC voltage
(C) Constant current
(D) Variable frequency
457. : The main losses in a transformer are: (WAPDA Electrical Engineer – 2020)
(A) Copper and iron losses
(B) Dielectric and leakage losses
(C) Friction and windage losses
(D) Corona and hysteresis losses
458. : The efficiency of a transformer increases when: (LESCO Electrical Engineer – 2021)
(A) Load increases to full load
(B) Load decreases
(C) Core material is removed
(D) Voltage is decreased
459. : In a DC shunt motor, the field winding is connected: (PPSC Electrical Engineer – 2021)
(A) In parallel with the armature
(B) In series with the armature
(C) Across the supply with resistor only
(D) Between supply and ground
460. : In a DC series motor, the field winding is connected: (NTDC Electrical Engineer – 2023)
(A) In parallel with the armature
(B) In series with the armature
(C) Across the supply with resistor
(D) Between supply and ground
461. : The speed of a DC shunt motor is: (PESCO Electrical Engineer – 2022)
(A) Almost constant
(B) Highly variable with load
(C) Zero at full load
(D) Infinite at no load
462. : The speed of a DC series motor is: (LESCO Electrical Engineer – 2021)
(A) Constant
(B) Varies with load
(C) Always zero at start
(D) Independent of load
463. : The back EMF of a DC motor opposes: (PPSC Electrical Engineer – 2021)
(A) Supply voltage
(B) Armature current
(C) Torque
(D) Rotor speed
464. : The main purpose of a starter in a DC motor is: (WAPDA Electrical Engineer – 2020)
(A) Limit high starting current
(B) Increase speed
(C) Reduce torque
(D) Control power factor
465. : The slip of a 3-phase induction motor is defined as: (NTDC Electrical Engineer – 2023)
(A) (Ns – Nr) / Ns
(B) (Nr – Ns) / Nr
(C) Ns / Nr
(D) Nr / Ns
466. : The starting torque of a squirrel cage induction motor is: (PESCO Electrical Engineer – 2022)
(A) Very high
(B) Moderate
(C) Very low
(D) Infinite
467. : The direction of rotation of a 3-phase induction motor can be reversed by: (WAPDA Electrical Engineer – 2020)
(A) Swapping any two supply phases
(B) Changing rotor resistance
(C) Increasing supply voltage
(D) Changing frequency
468. : The rotor of a squirrel cage induction motor consists of: (LESCO Electrical Engineer – 2021)
(A) Laminated core with bars short-circuited at ends
(B) Solid copper rotor
(C) Ferrite core rotor
(D) Wound rotor with slip rings
469. : The synchronous speed of a 6-pole induction motor at 50 Hz is: (PPSC Electrical Engineer – 2021)
(A) 500 rpm
(B) 1000 rpm
(C) 1500 rpm
(D) 3000 rpm
470. : In a synchronous motor, the rotor rotates at: (NTDC Electrical Engineer – 2023)
(A) Synchronous speed
(B) Less than synchronous speed
(C) Greater than synchronous speed
(D) Independent of supply frequency
471. : The excitation of a synchronous motor is provided by: (PESCO Electrical Engineer – 2022)
(A) DC supply
(B) AC supply
(C) Capacitor bank
(D) Induction effect
472. : The main advantage of a synchronous motor over an induction motor is: (LESCO Electrical Engineer – 2021)
(A) Ability to operate at unity power factor
(B) Simpler construction
(C) Lower cost
(D) No excitation required
473. : In a DC shunt motor, if the field winding is opened while running, the motor will: (PPSC Electrical Engineer – 2021)
(A) Run at dangerously high speed
(B) Stop immediately
(C) Reverse direction
(D) Continue at same speed
474. : The purpose of power factor correction is to: (WAPDA Electrical Engineer – 2020)
(A) Reduce current and losses
(B) Reduce voltage
(C) Increase frequency
(D) Control torque
475. : The main function of a relay in a power system is to: (NTDC Electrical Engineer – 2023)
(A) Measure voltage
(B) Detect faults and operate circuit breakers
(C) Regulate frequency
(D) Increase efficiency
476. : A Buchholz relay is used in: (PESCO Electrical Engineer – 2022)
(A) Generators
(B) Transformers
(C) Transmission lines
(D) Synchronous motors
477. : The surge impedance of a transmission line is: (LESCO Electrical Engineer – 2021)
(A) Ratio of voltage to current under surge conditions
(B) Product of voltage and current
(C) Ratio of current to resistance
(D) None of these
478. : The Ferranti effect in a transmission line causes: (WAPDA Electrical Engineer – 2020)
(A) Voltage drop at receiving end
(B) Voltage rise at receiving end during light load
(C) Increase in current
(D) Decrease in power factor
479. : The skin effect in transmission lines causes: (PPSC Electrical Engineer – 2021)
(A) Uniform current distribution
(B) Decrease in current density near conductor surface
(C) Increase in current density near conductor surface
(D) Current flow in the center only
480. : Corona loss in transmission lines increases with: (NTDC Electrical Engineer – 2023)
(A) Decrease in conductor spacing
(B) Increase in frequency
(C) Both (A) and (B)
(D) Decrease in voltage
481. : Which type of insulator is used for very high voltage transmission lines? (PESCO Electrical Engineer – 2022)
(A) Pin type
(B) Suspension type
(C) Shackle type
(D) Strain type
482. : The efficiency of a transmission line is maximum when: (LESCO Electrical Engineer – 2021)
(A) Sending end voltage = Receiving end voltage
(B) Line losses are zero
(C) Variable loss = Constant loss
(D) Reactive power = Zero
483. : 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
484. : 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
485. : The main function of a transmission line is to: (PPSC Lecturer Electrical Engineer – 2022)
(A) To generate power
(B) To transfer electric power from generating stations to substations
(C) To measure current
(D) To control voltage fluctuations
486. : The surge impedance of a transmission line is: (PPSC Instructor Electrical Engineer – 2021)
(A) Ratio of voltage to resistance
(B) Ratio of voltage to current under surge conditions
(C) Product of voltage and current
(D) None of these
487. : Which material is commonly used for overhead transmission lines? (PPSC Lecturer Electrical Engineer – 2020)
(A) Copper
(B) Aluminium
(C) Silver
(D) Iron
488. : The Ferranti effect occurs due to: (PPSC Instructor 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) Improvement of power factor
489. : Skin effect in transmission lines causes: (PPSC Lecturer Electrical Engineer – 2021)
(A) Uniform current distribution
(B) Increase in current at the conductor center
(C) Increase in current density near the surface of the conductor
(D) Decrease in current near surface
490. : Corona loss in transmission lines increases with: (PPSC Instructor Electrical Engineer – 2022)
(A) Decrease in line voltage
(B) Increase in frequency
(C) Decrease in conductor spacing
(D) Both (B) and (C)
491. : For very high voltage transmission lines, which type of insulator is commonly used? (PPSC Lecturer Electrical Engineer – 2021)
(A) Pin type
(B) Suspension type
(C) Shackle type
(D) Strain type
492. : The main purpose of a Buchholz relay in a transformer is to: (PPSC Instructor Electrical Engineer – 2020)
(A) Detect overheating in alternators
(B) Detect internal faults in transformers
(C) Measure power factor
(D) Protect induction motors
493. : The efficiency of a transmission line is maximum when: (PPSC Lecturer 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
494. : The dielectric strength of transformer oil should be at least: (PPSC Instructor Electrical Engineer – 2023)
(A) 5 kV
(B) 15 kV
(C) 30 kV
(D) 50 kV
495. : The synchronous speed of a 4-pole alternator operating at 50 Hz is: (PPSC Instructor Electrical Engineer – 2021)
(A) 1500 rpm
(B) 3000 rpm
(C) 1000 rpm
(D) 750 rpm
496. : The main function of a transmission line is to: (PPSC Lecturer Electrical Engineer – 2022)
(A) To generate power
(B) To transfer electric power from generating stations to substations
(C) To measure current
(D) To control voltage fluctuations
497. : Which material is commonly used for overhead transmission lines? (PPSC Instructor Electrical Engineer – 2020)
(A) Copper
(B) Aluminium
(C) Silver
(D) Iron
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