Electrical EngineeringI Smart Series MCQs COMPETITIVE EXAMS SET 10(901-1000)

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Smart series MCQs set 10 for all electrical engineering tests for post of Junior engineer/SDO in WAPDA ,GEPCO jobs NTS, NTDC,MEPCO,IESCO,PESCO and all DESCOS

  1. Which single phase motor has relatively high-power factor?
    A. Universal motor
    B. Split phase motor
    C. Repulsion motor
    D. Synchronous motor Ans. A
  2. Out of following which one is not an unconventional source of energy
    A. Tidal power
    B. Geothermal energy
    C. Nuclear energy
    D. Wind power Ans. C
  3. Overall thermal efficiency of a steam Power station is in the range of A. 18 -24%
    B. 30- 40%
    C. 44-62%
    D. 68 – 79%
    Ans. A
  4. Most of the generators in thermal power plants run at
    A. 3000 rpm
    B. 1500 rpm
    C. 1000 rpm
    D. 750 rpm Ans. A
  5. In power station practice “spinning reserve” is
    A. Reserve generating capacity that is in operation but not in reserve
    B. Reserve generating capacity that is connected to bus and ready to take the load
    C. Reserve generating capacity that is available for service but not in operation
    D. Capacity of part of plant that remains under maintenance Ans. B
  6. The overall efficiency of boiler in a thermal power plant is of the order of A. 10%
    B. 25 to 30%
    C. 40 to 50%
    D. 70 to 80%
    Ans. D
  7. Cost of operation of which plant is least?
    A. Gas turbine plant
    B. Thermal power plant
    C. Nuclear power plant
    D. Hydroelectric plant Ans. D
  8. In a hydro-electric plant a conduit system for taking water from the intake works to the turbine is known as
    A. Dam
    B. Reservoir
    C. Penstock
    D. surge tank Ans. C
  9. In a thermal power plant cooling towers are used to
    A. Condense low pressure steam
    B. Cool condensed steam
    C. Cool water used in condenser for condensing steam
    D. Cool feed water of boiler Ans. C
  10. Advantage(s) of hydroelectric power station is
    A. Low operating cost
    B. Free from pollution problems
    C. No fuel transportation problems
    D. All of above Ans. D
  11. When coal analysis gives fixed carbon, volatile combustible matter,
    and moisture the analysis is termed as
    A. Ultimate analysis
    B. Proximate analysis
    C. Orsat analysis
    D. Gross analysis Ans. B
  12. Generally, the major constituent of exhaust gases from a thermal power plant is
    A. Oxygen
    B. Carbon Monoxide
    C. Nitrogen
    D. Carbon dioxide Ans. C
  13. In hydro plants
    A. Initial cost is high and operating cost is low
    B. Initial cost as well as operating cost is high
    C. Initial cost is low and operating cost is high
    D. Initial cost as well as operating cost is low Ans. A
  14. In which of the following power plants, availability of power Is least reliable?
    A. Solar power plant
    B. Wind power plant
    C. Tidal power plant
    D. Geothermal power plant Ans. B
  15. The major disadvantage with solar cells for power generation is
    A. Lack of availability
    B. Large area requirement
    C. Variable power
    D. High cost Ans. D
  16. The total power of a wind stream is proportional to
    A. Velocity of stream
    B. (Velocity of stream)2
    C. (Velocity of stream)3
    D. None of above Ans. C
  17. Load factor during a period is
    A. Average load/ Installed capacity
    B. Average load/Maximum load
    C. Maximum load/Average load
    D. Maximum load/Installed capacity Ans. B
  18. Which plant can never have 100% load factor?
    A. Nuclear power plant
    B. Hydro- electric plant
    C. Peak load plant
    D. Base load plant Ans. C
  19. Which equipment provides fluctuating load?
    A. Lathe machine
    B. Exhaust fan
    C. Welding transformer
    D. All of above Ans. C
  20. In a power plant a reserve generating capacity which is in operation but not in service is known as
    A. Hot reserve
    B. Cold reserve
    C. Spinning reserve
    D. Firm power Ans. A
  21. A steam power station will run with maximum efficiency when it is run
    A. At low steam pressure
    B. At higher speeds
    C. On pulverized coal
    D. Near full load Ans. D
  22. Which of the following is likely to result in lower efficiency of a power station?
    A. Varying loads
    B. Low voltage generation
    C. Low turbine speeds
    D. Non-automatic controls Ans. A
  23. The life of underground cable is taken as
    A. 1 year
    B. 2 years
    C. 5 years
    D. 40 years Ans. D
  24. A diesel power plant is best suited as
    A. Base load plant
    B. Stand-by plant
    C. Peak load plant
    D. General purpose plant Ans. B
  25. Which power plant cannot have single unit of 100 MW?
    A. Steam power plant

B. Nuclear power plant
C. Hydroelectric power plant
D. Diesel power plant Ans. D

  1. Hydrogen is used for cooling of large sized generators because
    A. It has high thermal conductivity
    B. It is light
    C. It offers reduced fire risk
    D. All of above Ans. D
  2. A nuclear power plant is invariably used as a
    A. Base load plant
    B. Peak load plant
    C. Stand by plant
    D. Spinning reserve plant Ans. A
  3. For the same plant size, initial cost of which plant is the highest?
    A. Steam power plant
    B. Diesel engine plant
    C. Nuclear power plant
    D. Gas turbine plant Ans. C
  4. Base load plants have
    A. High capital cost, high operating cost and high load factor
    B. High capital cost, low operating cost and high load factor
    C. Low capital cost low operating cost and low load factor
    D. Low capital cost, high operating cost and high load factor Ans. B
  5. Which of the following is protective device against lightening over voltages?
    A. Rod gaps
    B. Surge absorbers
    C. Horn gaps
    D. All of above Ans. D
  6. In power plants insurance cover is provided for
    A. Equipment only
    B. Skilled workers only
    C. Unskilled workers only
    D. All of above Ans. D
  7. Skin effect results in
    A. Reduced effective resistance but increased effective internal reactance of the conductor

B. Increased effective resistance but reduced effective internal reactance of conductor
C. Reduced effective resistance as well as effective internal reactance
D. Increased effective resistance as well as effective reactance Ans. B

  1. Strain type insulators are used where the conductors are
    A. Dead ended
    B. At intermediate anchor towers
    C. Any of the above
    D. None of above Ans. C
  2. The current drawn by line due to corona losses is
    A. Sinusoidal
    B. Square
    C. Non-sinusoidal
    D. None of above Ans. C
  3. The effect of wind pressure is more predominant on
    A. Transmission lines
    B. Neutral lines
    C. Insulator
    D. Supporting towers Ans. D
  4. In transmission system a feeder feeds power to
    A. Service mains
    B. Generating stations
    C. Distributors
    D. All of above Ans. C
  5. In a transmission line following are the distributed constants
    A. Resistance and inductance only
    B. Resistance, inductance and capacitance
    C. Resistance, inductance, capacitance and short conductance
    D. None of above Ans. C
  6. A relay used on long transmission lines is
    A. Mho’s relay
    B. Reactance relay
    C. Impedance relay
    D. No relay is used Ans. A
  7. Total load transmitted through a 3 phase transmission line is 10,000 kW at 0.8 power factor lagging. The 12 R losses are 900kW. The efficiency of transmission line is
    A. 60%
    B. 90%
    C. 95%
    D. 99%
    Ans. B
  8. The power transmitted will be maximum when
    A. Sending end voltage is more
    B. Receiving end voltage is more
    C. Reactance is high
    D. Corona losses are least Ans. A
  9. Stranded conductors are used for transmitting power at high voltages because of
    A. Increased tensile strength
    B. Better in wind resistance
    C. Ease in handling
    D. Low cost Ans. C
  10. In case the height of transmission tower is increased
    A. The line capacitance and inductance will not change
    B. line capacitance will decrease but line inductance will remain unaltered Ans B
  11. Under no load conditions the current in a transmission line is due to
    A. Corona effects
    B. Capacitance of line
    C. Back flow from earth
    D. Spinning reserve
    Ans. B
  12. Which distribution system is more reliable?
    A. Ring main system
    B. Tree system
    C. Radial system
    D. All are equally reliable Ans. A
  13. In a substation the equipment used to limit short circuit current level is
    A. Series reactor
    B. Coupling capacitor
    C. Lightening switch
    D. Isolator Ans. A
  14. In order to increase the limit of distance of transmission line
    A. Series resistances are used
    B. Synchronous condensers are used
    C. Shunt capacitors and series reactors are used
    D. Series capacitors and shunt reactors are used

Ans. D

  1. All of the following are leading power factor systems except
    A. Under excited synchronous generator
    B. Series and shunt capacitors
    C. Induction motors
    D. Overexcited synchronous motors Ans. C
  2. The fault clearing time of a circuit breaker is usually
    A. One sec
    B. Few seconds
    C. Few mints
    D. Few cycles of supply voltage Ans. D
  3. In modern EHV system circuit breakers, the operating time between instant of receiving trip signal and final contact separation is
    A. 0.001 sec
    B. 0.015 sec
    C. 0.003 sec
    D. 0.03 sec Ans. D
  4. For motor circuit breakers, the time of closing the cycle is
    A. 0.001 sec
    B. 0.01 sec
    C. 0.10 sec
    D. 0.003 sec Ans. D
  5. The fuse current in amperes is related with fuse wire diameter as
    A. I  1/D
    B. I  D
    C. I  D3/2
    D. I  D2 Ans. C
  6. Fuse wire protection system is usually not used beyond
    A. 10 A
    B. 25 A
    C. 50 A
    D. 100 A Ans. D
  7. The number of cycles in which a high-speed circuit breaker can complete its operation is
    A. 3 to 8
    B. 10 to 18
    C. 20 to 30
    D. 40 to 50

Ans. A

  1. In a circuit breaker the current which exists at the instant of contact separation is known as
    A. Restriking current
    B. Surge current
    C. Breaking current
    D. Recovery current Ans. C
  2. A Merz-price protection is suitable for
    A. Transformers
    B. Alternators
    C. Feeders
    D. Transmission lines Ans. B
  3. Breaking capacity of a circuit breaker is usually expressed in terms of
    A. Amperes
    A. Volts
    B. MW
    C. MVA Ans. D
  4. The arc voltage produced in the circuit breaker is always
    A. In phase with the arc current
    B. Leading the arc current by 90°
    C. Lagging the arc current by 90°
    D. In between the lead and lag angles Ans. A
  5. In a circuit breaker the time duration from the instant of fault to the instant of energizing of trip coil is known as
    A. Lag time
    B. Lead time
    C. Protection time
    D. Operation time Ans. C
  6. In a circuit breaker, time duration from the instant of fault to the instant of closing of contact is known as
    A. Recycle time
    B. Total time
    C. Gross time
    D. Reclosing time Ans. D
  7. For a high-speed circuit breaker, the total clearing time is nearly
    A. 1 to 2 cycles
    B. 5 to 10 cycles
    C. 10 to 15 cycles

D. Less than 50 cycles Ans. A

  1. Which relay is used for feeders?
    A. MHO relay
    B. Translay relay
    C. Merz price protection
    D. Buchholz relay Ans. B
  2. A fuse wire should have
    A. Low specific resistance and high melting point
    B. Low specific resistance and low melting point
    C. High specific resistance and high melting point
    D. High specific resistance and low melting point Ans. D
  3. Cables can be generally used up to
    A. 400V
    B. 1000V
    C. 11kV
    D. 33kV Ans. D
  4. The size of conductor of power cables depends on
    A. Type of insulation
    B. Current
    C. Voltage
    D. Power factor Ans. B
  5. A zero-watt lamp consumes.
    A. No power
    B. About 5 to 7 watts of power
    C. About 15 to 20 watts of power
    D. About 25 to 30 watts of power Ans. B
  6. A DC generator used for AC welding should have
    A. Rising characteristics
    B. Drooping characteristics
    C. Straight characteristics
    D. None of above Ans. B
  7. The power factor of load using welding transformer least depends on
    A. Arc length
    B. Type of electrode
    C. No. of operating stations
    D. Material to be welded

Ans. D

  1. Which type of wattmeter cannot be used for both A.C and D.C?
    A. Dynamometer type
    B. Electrostatic type
    C. Induction type
    D. None of above Ans. C
  2. When the damping of an instrument is adjusted to enable the pointer rise quickly to its deflected position without overshooting, in that case the instrument is said to be
    A. Dead beat
    B. Off beat
    C. Over damped
    D. Under damped Ans. A
  3. When damping force is more than optimum, instrument will become
    A. Oscillating
    B. Fast and sensitive
    C. Slow and lethargic Ans. C
  4. When shunt resistance of a galvanometer circuit is increased, its
    A. Current sensitivity increases
    B. Current sensitivity decreases
    C. Damping increases
    D. Controlling torque decreases Ans. B
  5. Bridge used to measure dielectric loss of an insulator is
    A. Anderson bridge
    B. Wein’s bridge
    C. Schearing bridge
    D. Any of above Ans. A
  6. Synchro is a transducer
    A. Variable reluctance
    B. Angular position
    C. Parabolic
    D. Synchronizing Ans. B
  7. A Ryan Crest voltmeter is used to measure
    A. Peak voltage
    B. RMS voltage
    C. DC voltage
    D. All of above Ans. A
  8. In a three-phase half wave rectifier, each diode conducts for a duration of A. 180°
    B. 120°
    C. 90°
    D. 60°
    Ans. B
  9. Which of the following finds application in speed control of DC motor?
    A. FET
    B. NPN transistor
    C. SCR
    D. None of above Ans. C
  10. A device that does not exhibit negative resistance characteristics is
    A. FET
    B. WI
    C. Tunnel diode
    D. SCR Ans. A
  11. Thyristor is turned off when anode current falls below
    A. Forward current
    B. Latching current
    C. Holding current
    D. Break over current Ans. C
  12. In thyristor, dv/dt protection is achieved through the use of
    A. L across thyristor
    B. R across thyristor
    C. RC across thyristor
    D. RL across thyristor Ans. C
  13. For a three phase, 6 pulse diode rectifier, average output voltage is

Ans. B

  1. In 1 phase full converter, for load current I ripple free, average thyristor current is A. (1/4) I
    B. (1/2) I
    C. (3/4) I
    D. I Ans. B
  2. In 1 phase full converter, number of SCRs conducting during overlap
    A. 2
    B. 4
    C. 6
    D. 8 Ans. B
  3. When one of three series resistors is removed from a circuit and the circuit is reconnected, the current
    A. Increases
    B. Increase by one third
    C. Decreases by one third
    D. Decreases by the amount of current through the removed resistor Ans. A
  4. The total power in a certain circuit is 12 W. Each of the four equal value series resistors making up the circuit dissipates
    A. 12 W
    B. 48 W
    C. 3 W
    D. 8 W Ans. C
  5. All the voltage drops and the source voltage added together in a series circuit is equal to
    A. The total of the voltage drops
    B. The source voltage
    C. Zero
    D. The total of source voltage and voltage drops Ans. C
  6. If a 24 V and a 6 V battery are series opposing, the total voltage is
    A. 30 V
    B. 24 V
    C. 18 V
    D. 0 Ans. C
  7. The output of a certain voltage divider is 12 V with no load. When a load is connected, the output voltage
    A. Decreases
    B. Increases
    C. Remains same
    D. Becomes zero Ans. A
  8. The parallel combination of a 470 ohms resistor and a 1.5 k ohms resistor is in series with parallel combination of five 1 k resistors. The source voltage is 50 V. The percentage of the load current through any single 1 k resistor is
    A. 25%
    B. 20%

C. 100%
D. 50%
Ans. B

  1. In a certain series resonant circuit, VC = 125 V, VL = 125 V, and VR = 40 V. The value of source voltage is
    A. 125 V
    B. 250 V
    C. 290 V
    D. 40 V Ans. D
  2. In a series RC circuit 12 Vrms is measured across the resistor and 15 V(rms) is measured across the capacitor. The rms source voltage is
    A. 3v
    B. 27V
    C. 19.2V
    D. 1.9V Abs. C
  3. When the frequency of the source voltage decreases, the impedance of a parallel RC circuit
    A. Increases
    B. Decreases
    C. Does not change
    D. Decreases to zero Ans. A
  4. An AC circuit consists of a resistor and a capacitor. To increase the phase angle above 45°, the following condition must exist:
    A. R = XC
    B. R > XC
    C. R < XC
    D. R = 5XC Ans. C
  5. A 5mH, a 4.3mH and a 0.6mH inductors are connected in parallel. The total inductance is
    A. 9.9mH
    B. Greater than 5mH
    C. 9.9mH or greater than 5mH
    D. Less than 0.6mH Ans. D
  6. A 2mH, a 3.3mH and a 2.2mH inductors are connected in series. The total inductance is
    A. 55mH
    B. Less than 0.2mH
    C. Less than 5.5mH
    D. 7.5mH Ans. D
  7. The winding resistance of a coil can be increased by
    A. Increasing the number of turns
    B. Using a thinner wire
    C. Changing the core material
    D. Increasing the number of turns or using thinner wire Ans. D
  8. When the current through an inductor decreases, the amount of energy stored in the electromagnetic field
    A. Increases
    B. Decreases
    C. Remains the same
    D. Doubles Ans. B
  9. The inductance of an iron-core coil decreases if
    A. The number of turns is decreased
    B. The iron core is removed
    C. The length of the coil decreases
    D. None of the above Ans. A
  10. When the current through an inductor is cut in half, the amount of energy stored in the electromagnetic field
    A. Is quartered
    B. Quadruples
    C. Doubles
    D. Does not change Ans. A
  11. In applying the superposition theorem
    A. The sources are considered one at a time with all other’s replaced by their internal impedance
    B. All sources are considered independently
    C. All sources are considered simultaneously
    D. The sources are considered one at a time with all others replaced by their internal resistance
    Ans. A
  12. In order to get maximum power transfer from a capacitive source, the load must
    A. Have a capacitive reactance equal to circuit resistance
    B. Have an impedance that is the complex conjugate of the source impedance
    C. Be as capacitive as it is inductive
    D. None of the above Ans. B

Electrical EngineeringI Smart Series MCQs COMPETITIVE EXAMS SET 11(1000-1100)

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