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 157 of 158
- A. specific volume
- B. electrical conductivity
- C. co-efficient of linear expansion
- D. resistance per unit length for same cross-section
Explanation: Aluminium has lower electrical conductivity than copper, so conductivity is the exception.
Correct answer: electrical conductivity3122. For transmission of power over a distance of 200 km, the transmission voltage should be_________kv?
- A. 132 kV
- B. 66 kV
- C. 33 kV
- D. 11 kV
Explanation: For a transmission distance of about 200 km, 132 kV is a typical suitable voltage level.
Correct answer: 132 kV- A. 1.5
- B. 2.7
- C. 4.2
- D. 7.8
Explanation: Aluminium has a specific gravity of approximately 2.7, much lower than copper at about 8.9.
Correct answer: 2.7- A. 1 kV
- B. 11 kV
- C. 22 kV
- D. 33 kV
Explanation: Pin insulators are commonly used up to about 33 kV; for higher transmission voltages, suspension insulators are preferred because they…
Correct answer: 33 kV- A. non-sinusoidal
- B. sinusoidal
- C. triangular
- D. square
Explanation: Corona produces sharp current pulses as the surrounding air repeatedly ionises, so the resulting line current is non-sinusoidal rather…
Correct answer: non-sinusoidal- A. dead ended
- B. at intermediate anchor towers
- C. any of the above
- D. none of the above
Explanation: Strain insulators are used where conductor tension is highest, such as dead ends and intermediate anchor or angle towers.
Correct answer: any of the above- A. inductors
- B. capacitors
- C. synchronous motors
- D. all of above
- E. none of the above
Explanation: Voltage drop caused by reactive power can be reduced by an overexcited synchronous motor, which supplies leading reactive power and…
Correct answer: synchronous motors- A. 6.6 kV (r.m.s. value)/cm
- B. 11 kV (r.m.s. value)/cm
- C. 22 kV (maximum value)/cm
- D. 30 kV (maximum value)/cm
Explanation: Corona begins when the electric stress at the conductor surface reaches roughly 30 kV/cm maximum value in air.
Correct answer: 30 kV (maximum value)/cm- A. exciters
- B. series capacitors
- C. shunt reactors
- D. voltatre transformers
Explanation: Exciters belong primarily to generating stations, where they supply field current to alternators.
Correct answer: exciters- A. line is energized
- B. there is no current in the line
- C. line is on full load
- D. circuit breaker is not open
Explanation: An isolator is an off-load switching device and has no arc-quenching facility for interrupting current.
Correct answer: there is no current in the line- A. Current only
- B. Current and voltage
- C. Current, voltage and frequency
- D. Current, voltage, frequency and short time current
Explanation: A bus-bar is specified by its continuous current, rated voltage and frequency, along with its short-time withstand current for fault…
Correct answer: Current, voltage, frequency and short time current- A. compensate for skin effect
- B. neutralise proximity effect
- C. reduce line inductance
- D. increase the tensile strength
Explanation: Aluminium has good conductivity but relatively low mechanical strength, so a steel core is added in ACSR conductors to carry tensile loads…
Correct answer: increase the tensile strength- A. Using a guard ring
- B. Grading the insulator
- C. Using long cross arm
- D. Any of the above
- E. None of the above
Explanation: A guard ring, insulator grading, and a suitably long cross-arm all make the voltage distribution across a suspension-insulator string more…
Correct answer: Any of the above3134. 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 cur¬rent
- D. any of the above
- E. none of the above
Explanation: Alternating current produces greater inductive opposition toward the conductor’s centre, so current crowds toward the outer surface.
Correct answer: portion of the conductor near the surface carries more current and core of the conductor carries less current- A. Ring bus-bar scheme
- B. Single bus-bar scheme
- C. Breaker and a half scheme
- D. Main and transfer scheme
Explanation: The single bus-bar scheme has the simplest arrangement with the fewest circuit breakers and isolators, so it has the lowest installation…
Correct answer: Single bus-bar scheme- A. insulin
- B. bitumen
- C. varnish
- D. no insulation is required
Explanation: In an ACSR conductor, aluminium strands are laid around a galvanised steel core without an insulating layer between them.
Correct answer: no insulation is required- A. semi-circle
- B. triangle
- C. ellipse
- D. catenary
Explanation: A flexible conductor carrying its own weight between supports assumes a catenary shape.
Correct answer: catenary- A. 20-25 km
- B. 40-50 km
- C. 60-70 km
- D. 80-100 km
Explanation: An 11 kV line is generally used for relatively short transmission or primary-distribution distances, commonly up to about 20 to 25 km.
Correct answer: 20-25 km3139. 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
Explanation: Transmission-line supports should be economical, mechanically strong enough for conductor and weather loads, and durable over a long…
Correct answer: All of the above- A. Radial system
- B. Tree system
- C. Ring main system
- D. All are equally reliable
Explanation: A ring-main distribution system can feed a load from either direction, so supply can often continue when one section develops a fault.
Correct answer: Ring main system