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 25 of 158
- A. A 100 H.P. AC. three phase motor
- B. Four motors of 25 H.P. each
- C. Five motors of 20 H.P. each
- D. Ten motors of 10 H.P. each
Explanation: A single 100 HP three-phase motor is usually cheaper than several motors with the same total rating because it needs fewer frames…
Correct answer: A 100 H.P. AC. three phase motor- A. Shaded pole motor
- B. Repulsion motor
- C. Capacitor start motor
- D. None of the above
Explanation: A repulsion motor has a torque-speed characteristic resembling that of a series motor, including high starting torque and a speed that…
Correct answer: Repulsion motor- A. Totally enclosed
- B. Totally enclosed fan cooled
- C. Open type
- D. Semi closed
Explanation: A totally enclosed fan-cooled enclosure prevents contact with live or rotating parts and protects against dust and moisture while the…
Correct answer: Totally enclosed fan cooled- A. r.p.m. only
- B. Horse power only
- C. Horse power and r.p.m.
- D. Horse power, r.p.m. and power factor
Explanation: Shaft size is governed mainly by the torque that must be transmitted, and torque is proportional to horsepower divided by speed.
Correct answer: Horse power and r.p.m.- A. Tapped field control
- B. Diverter field control
- C. Series-parallel control
- D. Any of the above
Explanation: A series motor's flux can be controlled by tapping the field winding, diverting part of the current around it, or using series-parallel…
Correct answer: Any of the above- A. Oil expeller
- B. Floor mill
- C. Lifts and hoists
- D. Centrifugal pump
Explanation: Lifts and hoists must accelerate suspended loads quickly and safely, so they require high starting torque and high acceleration.
Correct answer: Lifts and hoists- A. Starting voltage is reduced
- B. Starting current is reduced
- C. Both A. and B.
- D. None of the above
Explanation: A star-delta starter initially connects the motor in star, reducing each winding's voltage to 1/√3 of the delta value.
Correct answer: Both A. and B.- A. D.C. motor
- B. Squirrel cage induction motor
- C. Wound rotor induction motor
- D. Synchronous motor
Explanation: A DC motor permits smooth and wide-range speed control through armature voltage, field flux, or both.
Correct answer: D.C. motor- A. Single phase motor
- B. Synchronous motor
- C. A.C. slip ring motor
- D. Ward-Leonard controlled D.C. shunt motor
Explanation: A slip-ring induction motor provides high starting torque and allows useful speed control by adding resistance to the rotor circuit…
Correct answer: A.C. slip ring motor- A. type of drive
- B. span
- C. tonnes
- D. any of the above
Explanation: Crane capacity means the maximum load the crane can safely lift, so it is specified in tonnes.
Correct answer: tonnes491. Which of the following motors is preferred when quick speed reversal is the main consideration ?
- A. Squirrel cage induction motor
- B. Wound rotor induction motor
- C. Synchronous motor
- D. D.C. motor
Explanation: A DC motor can reverse quickly by reversing armature connections or control voltage while retaining strong torque.
Correct answer: D.C. motor- A. Squirel cage induction motor
- B. Schrage motor
- C. Synchronous motor
- D. None of the above
Explanation: A synchronous motor cannot develop starting torque at standstill, so a pony motor first brings its rotor close to synchronous speed.
Correct answer: Synchronous motor- A. Lower cost
- B. Better efficiency
- C. High power factor
- D. All of the above
Explanation: A synchronous motor can operate at a leading power factor by overexciting its field, which improves the power factor of the supply system.
Correct answer: High power factor- A. Synchronous motor
- B. D.C. differentially compound motor
- C. Ward-Leonard controlled D.C. shunt motor
- D. AC. slip ring motor
Explanation: Crane travel requires high starting torque and controlled acceleration, which are provided well by an AC slip-ring induction motor through…
Correct answer: AC. slip ring motor- A. Precise control
- B. Smooth movement
- C. Fast speed control
- D. All of the above
Explanation: Crane hoisting and lowering require precise positioning, smooth movement to avoid load swing, and rapid speed control.
Correct answer: All of the above- A. slop speed operation
- B. high starting torque
- C. low windage losses
- D. all of the above
Explanation: A wound-rotor induction motor allows external resistance to be added to the rotor circuit, producing high starting torque and controlled…
Correct answer: high starting torque- A. ore handling plants
- B. steel plants
- C. heavy engineering workshops
- D. all of the above
Explanation: Heavy-duty cranes are needed wherever very large loads must be lifted and transported, including ore-handling plants, steel plants, and…
Correct answer: all of the above- A. Synchronous motor
- B. Slip ring induction motor
- C. Pole changing induction motor
- D. Squirrel cage induction motor
Explanation: A synchronous motor is preferred for a motor-generator set because it maintains nearly constant speed and can operate at a desired power…
Correct answer: Synchronous motor- A. auto-transformer
- B. star-delta
- C. slip ring
- D. any of the above
Explanation: Star-delta and autotransformer starting reduce the voltage applied to the stator, whereas a slip-ring motor normally receives full stator…
Correct answer: slip ring- A. Exhaust fan
- B. Ceiling fan
- C. Refrigerator
- D. Water pump
Explanation: A ceiling fan commonly uses variable speed so its airflow can be adjusted according to comfort.
Correct answer: Ceiling fan