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Top MCQ Basic Electricity For All Gov. Jobs

1. Which of the following materials is not used for transmission and distribution of electrical power?
A. Copper
B. Aluminium
C. Steel
D. Tungsten
Answer – (D)
2. For transmission of power over a distance of 200 km, the transmission voltage should be
A. 132 kV
B. 66 kV
C. 33 kV
D. 11 Kv
Answer – (A)
3. The steel used in steel cored conductors is usually
A. Alloy steel
B. Stainless steel
C. Mild steel
D. High speed steel
Answer – (C)
4. In a D.C. 3-wire distribution system, balancer fields are cross-connected in order to
A. boost the generated voltage
B. balance loads on both sides of the neutral
C. make both machine^ run as unloaded motors
D. equalize voltages on the positive and negative outers
Answer – (D)
5. The angular displacement between two interconnected stations is mainly due to
A. Armature reactance of both alternators
B. Reactance of the interconnector
C. Synchronous reactance of both the alternators
D. All of the above
Answer – (A)
6. Which of the following is not a constituent for making
porcelain insulators?
A. Quartz
B. Kaolin
C. Felspar
D. Silica
Answer – (D)
7. In transmission lines the cross-arms are made of
A. Copper
B. Wood
C. R.C.C.
D. Steel
Answer – (D)
8. The underground system cannot be operated above
A. 440 V
B. 11 V
C. 33 V
D. 66 V
Answer – (D)
9. For transmission of power over a distance of 500 km, the transmission voltage should be in the range
A. 150 to 220 Kv
B. 100 to 120 kV
C. 60 to 100 kV
D. 20 to 50 Kv
Answer – (A)
10. Which of the following D.C. distribution system is the simplest and lowest in first cost?
A. Radial system
B. Ring system
C. Interconnected system
D. None of the above
Answer – (A)
11. Owing to skin effect
A. Current flows through the half cross-section of the conductor
B. Portion of the conductor near the surface carries more current and core of the conductor carries less current
C. Portion of the conductor near the surface carries less current and core of the conductor carries more current
D. Any of the above
Answer – (B)
12. The spacing between phase conductors of a 220 kV line is approximately equal to
A. 2 m
B. 3.5 m
C. 6 m
D. 8.5 m
Answer – (C)
13. The skin effect of a conductor will reduce as the
A. Resistivity of conductor material increases
B. Permeability of conductor material increases
C. Diameter increases
D. Frequency increases
Answer – (A)
14. Which of the following is the demerit of a ‘constant voltage transmission system’?
A. Increase of short-circuit current of the system
B. Availability of steady voltage at all loads at the line terminal
C. Possibility of better protection for the line due to possible use of higher terminal reactants
D. Improvement of power factor at times of moderate and heavy loads
Answer – (A)
15. Electromechanical voltage regulators are generally used in
A. Reactors
B. Generators
C. Transformers
D. All of the above
Answer – (B)
16. The presence of ozone due to corona is harmful because it
A. Reduces power factor
B. Corrodes the material
C. Gives odour
D. Transfer energy to the ground
Answer – (B)
17. The following system is not generally used
A. 1-phase 3-wire
B. 1-phase 4-wire
C. 3-phase 3-wire
D. 3-phase 4-wire
Answer – (A)
18. A conductor, due to sag between two supports, takes the form of
A. Semicircle
B. Triangle
C. Ellipse
D. Catenary
Answer – (D)
19. The cause of damage to the lead sheath of a cable is
A. crystallisation of the lead through vibration
B. chemical action on the lead when buried in the earth
C. mechanical damage
D. all of the above
Answer – (D)
20. The operating voltage of super-tension cables is up to
A. 3.3 kV
B. 6.6 kV
C. 11 kV
D. 33 Kv
Answer – (D)
21. On which of the following factors skin effect depends?
A. Frequency of the current
B. Size of the conductor
C. Resistivity of the conductor material
D. All of the above
Answer – (D)
22. Which of the following characteristics should the line supports for transmission lines possess?
A. Low cost
B. High mechanical strength
C. Longer life
D. All of the above
Answer – (D)
23. A feeder, in a transmission system, feeds power to
A. Distributors
B. Generating stations
C. Service mains
D. All of the above
Answer – (A)
24. Transmission line insulators are made of
A. Glass
B. Porcelain
C. Iron
D. P.V.C.
Answer – (B)
25. Skin effect is proportional to
A. (conductor diameter)½
B. (conductor diameter)4
C. (conductor diameter)2
D. (conductor diameter)3
E. none of the above
Answer – (C)
26. The operating voltage of high voltage cables is up to
A. l.lkV
B. 3.3kV
C. 6.6kV
D. LlkV
Answer – (D)
27. If variable part of annual cost on account of interest and depreciation on the capital outlay is equal to the annual cost of electrical energy wasted in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be most economical. This statement is known as
A. Kelvin’s law
B. Ohm’s law
C. Kirchhoff’s law
D. Faraday’s law
Answer – (A)
28. Besides a method of trial and error, which of the following methods is employed for solution of network problems in interconnected system?
A. Circulating current method
B. Thevenin’s theorem
C. Superposition of currents
D. All of the above
Answer – (D)
29. Which of the following is the source of heat generation in the cables?
A. Dielectric losses in cable insulation
B. losses in the conductor
C. Losses in the metallic sheathings and armourings
D. All of the above
Answer – (D)
30. Which of the following faults is most likely to occur in cables?
A. Cross or short-circuit fault
B. Open circuit fault
C. Breakdown of cable insulation
D. All of the above
Answer – (D)
31. ________ are the conductors, which connect the consumer’s terminals to the distribution.
A. Distributors
B. Service mains
C. Feeders
D. None of the above
Answer – (B)
32. The square root of the ratio of line impedance and shunt admittance is called the
A. Surge impedance of the line
B. Conductance of the line
C. Regulation of the line
D. None of the above
Answer – (A)
33. The wooden poles well impregnated with creosote oil or any preservative compound has life
A. From 2 to 5 years
B. 10 to 15 years
C. 25 to 30 years
D. 60 to 70 years
Answer – (C)
34. The power transmitted will be maximum when
A. Corona losses are minimum
B. Reactance is high
C. Sending end voltage is more
D. Receiving end voltage is more
Answer – (C)
35. The loads on distributors systems are generally
A. Balanced
B. Unbalanced
C. Either of the above
D. None of the above
Answer – (B)
ALTERNATING CURRENT AND VOLTAGE
1. To produce an 800 Hz sine wave, a four-pole generator must be operated at
A. 200 rps
B. 400 rps
C. 800 rps
D. 1,600 rps
Answer – (B)
2. Sine wave A has a positive-going zero crossing at 45°. Sine wave B has a positive-going zero crossing at 60°. Which of the following statements is true?
A. Wave A leads wave B by 15°
B. Wave A lags wave B by 15°
C. Wave A leads wave B by 105°
D. Wave A lags wave B by 105°
Answer – (A)
3. A ramp is the type of waveform characterized by a non-linear increase or decrease in voltage or current.
A. True
B. False
Answer – (B)
4. Amplitude is the maximum value of a voltage or current.
A. True
B. False
Answer – (A)
5. The average half-cycle value of a sine wave with a 40 V peak is
A. 25.48 V
B. 6.37 V
C. 14.14 V
D. 50.96 V
Answer – (A)
6. A sine wave of 15 kHz is changing at a faster rate than a sine wave with a frequency of
A. 25 kHz
B. 12 kHz
C. 18 kHz
D. 1.3 MHz
Answer – (B)
7. When a sine wave has a frequency of 100 Hz in 12 s it goes through
A. 1/100 cycle
B. 12 cycles
C. 120 cycles
D. 1,200 cycles
Answer – (D)
8. If a sine wave goes through 10 cycles in 20 μs, the period is
A. 20 μs
B. 4 μs
C. 2 μs
D. 100 μs
Answer – (C)
9. A phasor represents
A. The magnitude and a quantity direction
B. The width of a quantity
C. The phase angle
D. The magnitude of a quantity
Answer – (A)
10. A waveform has a baseline of 3 V, a duty cycle of 20%,
and an amplitude of 8 V. The average voltage value is
A. 4 V
B. 4.6 V
C. 1.6 V
D. 11 V
Answer – (A)
11. Two series resistors are connected to an ac source. If there are 7.5 V rms across one resistor and 4.2 V rms across the other, the peak source voltage is
A. 16.54 V
B. 1.65 V
C. 10.60 V
D. 5.93 V
Answer – (A)
12. A 1 kHz signal has a period of 1 ms.
A. True
B. False
Answer – (A)
13. A sine wave with a period of 4 ms is changing at a faster rate than a sine wave with a period of
A. 0.0045 s
B. 2 ms
C. 1.5 ms
D. 3,000 μs
Answer – (A)
14. The instantaneous value is the voltage or current value of a waveform at its peak.
A. True
B. False
Answer – (B)
15. A signal with a 400 μs period has a frequency of
A. 250 Hz
B. 2,500 Hz
C. 25,000 Hz
D. 400 Hz
Answer – (B)
16. A sinusoidal current has an rms value of 14 mA. The peak-to-peak value is
A. 45.12 mA
B. 16 mA
C. 39.6 mA
D. 22.6 mA
Answer – (C)
17. If the peak of a sine wave is 13 V, the peak-to-peak value is
A. 6.5 V
B. 13 V
C. 26 V
D. None of the above
Answer – (C)
18. The conductive loop on the rotor of a simple two-pole, single-phase generator rotates at a rate of 400 rps. The frequency of the induced output voltage is
A. 40 Hz
B. 100 Hz
C. 400 Hz
D. Indeterminable
Answer – (C)
19. A sine wave with an rms value of 12 V is riding on a dc level of 18 V. The maximum value of the resulting waveform is
A. 6 V
B. 30 V
C. 35 V
D. 0 V
Answer – (C)
20. Average value of a sine wave is 0.707 times the peak value.
A. True
B. False
Answer – (B)
21. A square wave has a period of 60 μs. The first odd harmonic is
A. 5 kHz
B. 50 kHz
C. 500 kHz
D. 33.33 kHz
Answer – (B)
22. Periodic is characterized by a repetition at fixed time intervals.
A. True
B. False
Answer – (A)
23. The designation rms means repetitions measured per second.
A. True
B. False
Answer – (B)
24. A saw-tooth wave has a period of 10 ms. Its frequency is
A. 10 Hz
B. 50 Hz
C. 100 Hz
D. 1,000 Hz
Answer – (C)
25. The average value of a 12 V peak sine wave over one complete cycle is
A. 0 V
B. 1.27 V
C. 7.64 V
D. 6.37 V
Answer – (A)
26. The duty cycle of a pulse waveform with a pulse width of 10 μs and a period of 100 μs is 25%.
A. True
B. False
Answer – (B)
27. If the rms voltage drop across a 15 kΩ resistor is 16 V, the peak current through the resistor is
A. 15 Ma
B. 1.5 mA
C. 10 mA
D. 1 mA
Answer – (B)
28. The angular position of a phasor represents the angle of the sine wave with respect to a reference.
A. True
B. False
Answer – (A)
29. The unit of frequency is the hertz.
A. True
B. False
Answer – (A)
30. How many degrees are there in p/3 rad?
A. 6°
B. 60°
C. 180°
D. 27°
Answer – (B)
31. If the rms current through a 6.8 kΩ resistor is 8 mA, the rms voltage drop across the resistor is
A. 5.44 V
B. 54.4 V
C. 7.07 V
D. 8 V
Answer – (B)
32. If the rms current through a 4.7 kΩ resistor is 4 mA, the peak voltage drop across the resistor is
A. 4 V
B. 18.8 V
C. 26.6 V
D. 2.66 V
Answer – (C)
33. A pulse waveform has a high time of 8 ms and a pulse width of 32 ms. The duty cycle is
A. 25%
B. 50%
C. 1%
D. 100%
Answer – (A)
34. The length of a phasor represents the amplitude.
A. True
B. False
Answer – (A)
35. One sine wave has a positive-going zero crossing at 15° and another sine wave has a positive-going zero crossing at 55°. The phase angle between the two waveforms is
A. 0°
B. 45°
C. 40°
D. None of the above
Answer – (C)
36. Duty cycle is the characteristic of a pulse waveform that indicates the high time versus the low time.
A. True
B. False
Answer – (B)
37. A 20 kHz pulse waveform consists of pulses that are 15 μs wide. The duty cycle
A. Is 1%
B. Is 30%
C. Is 100%
D. Cannot be determined
Answer – (B)
VOLTAGE, CURRENT RESISTANCE
1. The conductance of an 8 ohm resistance is
A. 12.5 mS
B. 8 mS
C. 12 S
D. 125 mS
Answer – (D)
2. If there is 6 A of current through the filament of a lamp, how many coulombs of charge move through the filament in 1.75 s?
A. 10.5 C
B. 105 C
C. 3.4 C
D. 34 C
Answer – (A)
3. A neutral atom with an atomic number of five has how many electrons?
A. 1
B. 5
C. None
D. Depends on the type of atom
Answer – (B)
4. Resistance limits the current.
A. True
B. False
Answer – (A)
5. A multimeter measures
A. Current
B. Voltage
C. Resistance
D. Current, voltage, and resistance
Answer – (D)
6. The minimum resistance value for a blue, gray, red, silver resistor is
Answer – (B)
7. When placed close together, two positively charged materials will
A. Attract
B. Become neutral
C. Become negative
D. Repel
Answer – (D)
8. A circuit breaker is a
A. Fuse
B. Switch
C. Resettable protective device
D. Resistor
Answer – (C)
9. Materials with lots of free electrons are called
A. Conductors
B. Insulators
C. Semiconductors
D. Filters
Answer – (A)
10. The colored bands for a 4,700 ohm resistor with a ten percent tolerance are
A. Yellow, violet, red, gold
B. Yellow, violet, orange, gold
C. Yellow, violet, red, silver
D. Orange, violet, red, silver
Answer – (C)
11. Free electrons make current possible.
A. True
B. False
Answer – (A)
12. A material that does not allow current under normal conditions is a/an
A. Insulator
B. Conductor
C. Semiconductor
D. Valence
Answer – (A)
13. A potentiometer is a two terminal variable resistor.
A. True
B. False
Answer – (B)
14. The current in a given circuit is not to exceed 24 A. Which value of fuse is best?
A. A fuse is not necessary
B. 10 A
C. 24 A
D. 20 A
Answer – (C)
15. An ammeter is an electrical instrument used to measure
A. Current
B. Voltage
C. Resistance
D. None of the above
Answer – (A)
16. An open circuit is one that has a complete current path.
A. True
B. False
Answer – (B)
17. A neutral atom is one with an equal number of protons and electrons.
A. True
B. False
Answer – (A)
18. The maximum resistance value for a brown, red, yellow,
gold resistor is
A. 126,000 Ω
B. 126,600 Ω
C. 114,000 Ω
D. 132,000 Ω
Answer – (B)
19. Which of the following is not a type of energy source?
A. Generator
B. Rheostat
C. Solar cell
D. Battery
Answer – (B)
20. A thermistor is a type of
A. Switch
B. Resistor
C. Battery
D. Power supply
Answer – (B)
21. A free electron is a valence electron that has broken away from its parent atom.
A. True
B. False
Answer – (B)
22. The atomic number is the number of neutrons in the nucleus.
A. True
B. False
Answer – (A)
23. An ohmmeter is an instrument for measuring
A. Current
B. Voltage
C. Resistance
D. Wattage
Answer – (B)
24. A red, red, orange, gold resistor has a nominal value of
A. 22,000 Ω
B. 2,200 Ω
C. 22 Ω
D. 2.2 Ω
Answer – (C)
25. A two terminal variable resistor is known as a
A. Potentiometer
B. Thermistor
C. Rheostat
D. Wiper
Answer – (A)
26. A wiper is the sliding contact in a
A. Switch
B. Photoconductive cell
C. Thermistor
D. Potentiometer
Answer – (D)
27. When the current is 2.5 A, how many coulombs pass a point in 0.2 s?
A. 12.5 C
B. 1.25 C
C. 0.5 C
D. 5 C
Answer – (C)
28. An ammeter is connected across the current path.
A. True
B. False
Answer – (B)
29. A voltmeter is connected across the current path.
A. True
B. False
Answer – (A)
30. Electrons in the outer orbit are called
A. Nuclei
B. Valences
C. Waves
D. Shells
Answer – (B)
31. The nominal value of a brown, black, yellow, and gold resistor is 100,000 ohms.
A. True
C. False
Answer – (A)
32. The unit of electrical charge is the
A. Coulomb
B. Joule
C. Volt
D. Watt
Answer – (A)
33. Eighttenths coulomb passes a point in 4 s. The current in amperes is
A. 1.6 A
B. 16 A
C. 2 A
D. 0.2 A
Answer – (D)
34. Current flows in a circuit when
A. A switch is opened
B. A switch is closed
C. The switch is either open or closed
D. There is no voltage
Answer – (B)
Ohms Law
1. How much current is produced by a voltage of 18 kV across a 15 kΩ resistance?
A. 1.2 A
B. 12 A
C. 120 Ma
D. 12 mA
Answer – (A)
2. What is the approximate filament resistance of a light bulb if it operates from a 110 V source and 0.6 A of current is flowing?
A. 183 Ω
B. 18.3 Ω
C. 66 Ω
D. 6.6 Ω
Answer – (A)
3. Four amperes of current are measured through a 24 Ω resistor connected across a voltage source. How much voltage does the source produce?
A. 960 V
B. 9.6 V
C. 96 V
D. 8 V
Answer – (C)
4. The ampere is the unit of resistance.
A. True
B. False
Answer – (B)
5. If you wish to increase the amount of current in a resistor from 120 mA to 160 mA by changing the 24 V source, what should the new voltage setting be?
A. 8 V
B. 320 V
C. 3.2 V
D. 32 V
Answer – (D)
6. A resistor is connected across a 50 V source. What is the current in the resistor if the color code is red, orange and silver?
A. 2 Ma
B. 2.2 mA
C. 214 mA
D. 21.4 mA
Answer – (B)
7. Approximately how many milli-amperes of current flow through a circuit with a 40 V source and 6.8 kΩ of resistance?
A. 27.2 mA
B. 59 mA
C. 5.9 mA
D. 590 mA
Answer – (C)
8. If 750 μA is flowing through 11 kΩ of resistance, what is the voltage drop across the resistor?
A. 8.25 V
B. 82.5 V
C. 14.6 V
D. 146 V
Answer – (A)
9. According to Ohm’s Law
A. V is directly proportional to I
B. V is inversely proportional to I
C. V is directly proportional to Vi
D. All of the above
Answer – (A)
10. Approximately how much current flows through a 3.3 MO resistor across a 30 V source?
A. 9 μA
B. 90 μA
C. 900 μA
D. 9000 μA
Answer – (A)
11. What is the approximate resistance of a rheostat if the voltage source is 18 V and the current is 220 mA?
A. 8.2 Kω
B. 820 Ω
C. 8.2 Ω
D. 82 Ω
Answer – (D)
12. A resistance of 3.3 MO is connected across a 500 V source. The resulting current is approximately
A. 15.1 μA
B. 151 μA
C. 66 Ma
D. 660 mA
Answer – (B)
13. An electric heater draws 3.5 A from a 110 V source. The resistance of the heating element is approximately
A. 385 Ω
B. 38.5 Ω
C. 3.1 Ω
D. 31 Ω
Answer – (D)
14. A current of 200 μA through a 6.8 kΩ resistor produces a voltage drop of
A. 34.4 V
B. 340 V
C. 13.6 V
D. 1.36 V
Answer – (D)
15. How much voltage is needed to produce 2.5 A of current through a 200 Ω resistor?
A. 50 V
B. 500 V
C. 80 V
D. 8 V
Answer – (B)
16. Twelve volts are applied across a resistor. A current of 3 mA is measured. What is the value of the resistor?
A. 4 Ω
B. 400 Ω
C. 4 Kω
D. 4.4 Ω
Answer – (C)
17. How much resistance is needed to draw 17.6 mA from a 12 volt source?
A. 212 Ω
B. 6.8 Kω
C. 68 Ω
D. 680 Ω
Answer – (D)
18. The formula for finding resistance when current and voltage are known is R = I/V.
A. True
B. False
Answer – (B)
19. The formula for finding voltage when resistance and current are known is V = I/R.
A. True
B. False
Answer – (B)
20. When there is 12 mA of current through a 1.2 kΩ resistor, the voltage across the resistor is
A. 14.4 V
B. 1.4 V
C. 100 V
D. 10 V
Answer – (A)
21. A 120 V lamp-dimming circuit is controlled by a rheostat and protected from excessive current by a 3 A fuse. To what minimum resistance value can the rheostat be set without blowing the fuse? Assume a lamp resistance of 20
ohms.
A. 40 Ω
B. 4 Ω
C. 2 Ω
D. 20 Ω
Answer – (D)
22. When 12 V are applied across a 68 Ω resistor, the current is
A. 816 Ma
B. 17.6 mA
C. 176 mA
D. 8.16 mA
Answer – (C)
23. If 24 V are applied across a resistor and there are 10.9 mA of current, the resistance is
A. 220 Kω
B. 22 kΩ
C. 2.2 kΩ
D. 220 Ω
Answer – (C)
24. Ohm’s law describes how current is related to voltage and resistance.
A. True
B. False
Answer – (A)
25. You are measuring the current in a circuit that is operated on an 18 V battery. The ammeter reads 40 mA. Later you notice the current has dropped to 20 mA. How much has the voltage changed?
A. 9 V
B. 900 Mv
C. 0 V
D. 18 V
Answer – (A)
26. What is the voltage source for a circuit carrying 2 A of current through a 36 Ω resistor?
A. 1.8 V
B. 18 V
C. 7.2 V
D. 72 V
Answer – (D)
27. The current through a flashlight bulb is 40 mA and the total battery voltage is 4.5 V. The resistance of the bulb is approximately
A. 112 Ω
B. 11.2 Ω
C. 1.2 Ω
D. 18 Ω
Answer – (A)
28. The formula to find I when the values of V and R are known is
A. I = VR
B. I = R/V
C. V = IR
D. I = V/R
Answer – (D)
29. How much resistance is required to limit the current from a 12 V battery to 3.6 mA?
A. 3.3 Kω
B. 33 kΩ
C. 2.2 kΩ
D. 22 kΩ
Answer – (A)
30. What is the approximate resistance setting of a rheostat in which 650 mA of current flows with a 150 V source?
A. 9.7 Ω
B. 97 Ω
C. 23 Ω
D. 230 Ω
Answer – (A)


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