All Free Electrical Engineering MCQs with Answers
Every Electrical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
3,143 questions · page 156 of 158
- A. Copper
- B. Aluminium
- C. Steel
- D. Tungsten
Explanation: Copper and aluminium are used as electrical conductors, while steel is used where mechanical strength is important, such as in…
Correct answer: Tungsten- A. from 2 to 5 years
- B. 10 to 15 years
- C. 25 to 30 years
- D. 60 to 70 years
Explanation: Creosote or preservative treatment protects wooden poles against moisture, fungi and insects, extending their service life to roughly 25…
Correct answer: 25 to 30 years- A. Kelvin's law
- B. Ohm's law
- C. Kirchhoffs law
- D. Faraday's law
- E. none of the above
Explanation: Kelvin's law states that the most economical conductor size occurs when annual capital charges due to interest and depreciation equal the…
Correct answer: Kelvin's law- A. 11 kV
- B. 33 kV
- C. 66 kV
- D. 400 kV
Explanation: Overhead lines are suitable for very high voltages because air provides insulation at comparatively low cost and the conductors can be…
Correct answer: 400 kV- A. 440 V
- B. 11 kV
- C. 33 kV
- D. 66 kV
Explanation: In conventional power-system comparisons, underground cables are generally considered uneconomical and difficult to operate above about 66…
Correct answer: 66 kV3106. _______________are the conductors, which connect the consumer's terminals to the distribution?
- A. Distributors
- B. Service mains
- C. Feeders
- D. None of the above
Explanation: Service mains are the conductors running from the distribution line or distributor to the consumer's terminals.
Correct answer: Service mains- A. Overhead system
- B. Underground system
- C. Both A. and (b)
- D. None of the above
Explanation: Electrical power can be transmitted by overhead lines or by underground cables.
Correct answer: Both A. and (b)- A. Current will flow to earth
- B. Supply voltage will drop
- C. Supply voltage will increase
- D. No current will flow in the conductor
- E. None of the above
Explanation: When a live conductor contacts earth, a fault current flows from the conductor into the ground and returns through the earthing path or…
Correct answer: Current will flow to earth- A. resistivity of conductor material increases
- B. permeability of conductor material increases
- C. diameter increases
- D. frequency increases
Explanation: Skin effect becomes weaker when resistivity increases because the skin depth is proportional to the square root of resistivity.
Correct answer: resistivity of conductor material increases3110. When a conductor carries more current on the surface as compared to core, it is due to___________?
- A. permeability variation
- B. corona
- C. skin effect
- D. unsymmetrical fault
- E. none of the above
Explanation: Skin effect causes alternating current to concentrate near the outer surface of a conductor, leaving less current in its core.
Correct answer: skin effect- A. large
- B. small
- C. fluctuating
- D. any of the above
Explanation: Series capacitors are mainly valuable for reducing transmission-line reactance and improving power transfer on heavily loaded lines.
Correct answer: small- A. fall
- B. rise
- C. remain unchanged
- D. none of the above
Explanation: When one alternator is disconnected from a common bus, the remaining generators maintain the bus voltage through their excitation systems…
Correct answer: remain unchanged- A. the transfer of power will take place with voltage fluctuation and noise
- B. the transfer of power will take place with least loss
- C. the stations will fall out of step be¬cause of large angular displacement between the stations
- D. none of the above
Explanation: For a given transferred power, a large interconnector reactance requires a larger power-angle difference.
Correct answer: the stations will fall out of step be¬cause of large angular displacement between the stations- A. Short transmission lines
- B. Medium transmission lines
- C. Long transmission lines
- D. Medium as well as long transmission lines
Explanation: Short transmission lines are usually treated as having negligible shunt capacitance because their length is small and the charging current…
Correct answer: Short transmission lines- A. 150 to 220 kV
- B. 100 to 120 kV
- C. 60 to 100 kV
- D. 20 to 50 kV
Explanation: A 500 km transmission line is a long-distance line and commonly operates at an extra-high voltage around 220 kV, fitting the 150 to 220 kV…
Correct answer: 150 to 220 kV- A. presence of ozone detected by odour
- B. hissing sound
- C. faint luminous glow of bluish colour
- D. all of the above
Explanation: Corona ionizes the surrounding air, producing ozone with a characteristic smell, a hissing noise, and a faint bluish glow.
Correct answer: all of the above- A. Frequency of the current
- B. Size of the conductor
- C. Resistivity of the conductor material
- D. All of the above
Explanation: Skin effect increases with frequency and conductor size, and it also varies with the material resistivity.
Correct answer: All of the above- A. large conductor area is required for same power transmission
- B. short-circuit current of the system is increased
- C. either of the above
- D. none of the above
Explanation: In constant-voltage transmission, a fault can produce a large current because the system voltage remains nearly fixed while the line…
Correct answer: short-circuit current of the system is increased- A. primary winding
- B. secondary winding
- C. high voltage winding
- D. any of the above
Explanation: Tappings are generally placed on the high-voltage winding because it carries lower current, making the tap contacts smaller and safer to…
Correct answer: high voltage winding- A. Static condenser
- B. Synchronous condenser
- C. Tap changing transformer
- D. Booster transformer
Explanation: A booster transformer is a comparatively simple and economical way to add or subtract a voltage component in a distribution feeder.
Correct answer: Booster transformer