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 27 of 158
- A. Single phase motors
- B. Squirrel cage induction motors
- C. Slip ring induction motors
- D. D.C. motors
Explanation: DC motors are traditionally preferred for rolling mills because they provide high starting torque, smooth wide-range speed control, and…
Correct answer: D.C. motors- A. High efficiency operation
- B. Reversibility
- C. Variable speed drive
- D. High starting torque
Explanation: DC motors remain especially useful where a wide and precise range of speed control is required, because their speed can be controlled…
Correct answer: Variable speed drive- A. Inner race
- B. Outer race
- C. Cage
- D. Bush
Explanation: A ball bearing contains inner and outer races, rolling balls, and a cage that keeps the balls separated.
Correct answer: Bush- A. less than running torque
- B. same as running torque
- C. slightly more than running torque
- D. double the running torque
Explanation: A centrifugal pump develops torque approximately proportional to the square of speed, so its torque demand is very small at starting and…
Correct answer: less than running torque- A. Frame
- B. Rearing
- C. Stator winding
- D. Rotor winding
Explanation: The bearing, apparently misspelled as “Rearing,” needs maximum maintenance attention because it is subject to friction, lubrication…
Correct answer: Rearing- A. Starting characteristics
- B. Operating speed
- C. Horse power
- D. Speed control
Explanation: A centrifugal pump normally operates near a fixed speed, so speed control is usually not important in motor selection.
Correct answer: Speed control- A. Light duty
- B. Medium duty
- C. Heavy duty
- D. All of the above
Explanation: Ward-Leonard DC drives provide high starting torque, smooth speed control and easy reversal, making them suitable for heavy-duty…
Correct answer: Heavy duty- A. Starting torque
- B. Conditions of environment
- C. Limitation on starting current
- D. Speed control range and its nature
- E. All of the above
Explanation: Motor and control-gear selection must consider the required starting torque, environmental conditions, allowable starting current and the…
Correct answer: All of the above- A. variable load
- B. continuous
- C. continuous but periodical
- D. intermittent and variable load
Explanation: A power press draws load only during the pressing stroke and the load also changes during that stroke, with idle or lighter periods…
Correct answer: intermittent and variable load- A. Running characteristics
- B. Starting characteristics
- C. Efficiency
- D. Braking
Explanation: A floor mill needs suitable starting and running characteristics and good efficiency for economical operation.
Correct answer: Braking531. The selection of an electric motor for any application depends on which of the following factors ?
- A. Electrical characteristics
- B. Mechanical characteristics
- C. Size and rating of motors
- D. Cost
- E. All of the above
Explanation: Motor selection involves electrical performance, mechanical requirements, physical size and rating, and economic cost.
Correct answer: All of the above- A. Squirrel cage induction motor
- B. Synchronous motors
- C. Ward-Leonard controlled D.C. motors
- D. Any of the above
Explanation: Ward-Leonard drives provide smooth, wide-range speed control, rapid reversal and good automatic control, making them suitable for…
Correct answer: Ward-Leonard controlled D.C. motors- A. 2 kW
- B. 20 kW
- C. 50 kW
- D. 100 kW
Explanation: Synchronous motors become economically attractive for large loads, commonly above about 100 kW, because their higher cost is offset by…
Correct answer: 100 kW- A. Power houses
- B. Pumping stations
- C. Automobile workshops
- D. All of the above
Explanation: Light-duty cranes are used for handling lighter loads in power houses, pumping stations and automobile workshops.
Correct answer: All of the above- A. Slow speed motors
- B. Continuous duty motors
- C. Short time rated motors
- D. None of the above
Explanation: Overhead travelling cranes operate intermittently with frequent starting, stopping and reversing, so their motors are designed for…
Correct answer: Short time rated motors- A. 15-20
- B. 50-75
- C. 120-150
- D. 160-200
Explanation: Suburban trains make frequent stops and starts, so their specific energy consumption is higher than that of long-distance services; a…
Correct answer: 50-75- A. 0.2 to 0.5 km phps
- B. 1.6 to 4.0 km phps
- C. 5 to 10 km phps
- D. 15 to 25 km phps
Explanation: Suburban and urban trains require relatively high acceleration to maintain schedules despite frequent stops, typically about 1.6 to 4.0…
Correct answer: 1.6 to 4.0 km phps538. Which of the following methods is used to control speed of 25 kV, 50 Hz single phase traction ?
- A. Reduced current method
- B. Tap changing control of transformer
- C. Series parallel operation of motors
- D. All of the above
Explanation: A 25 kV, 50 Hz single-phase traction system controls locomotive speed mainly by changing the transformer tap, which varies the voltage…
Correct answer: Tap changing control of transformer- A. 0.16 km phps
- B. 1.6 km phps
- C. 16 km phps
- D. 40 km phps
Explanation: During coasting, train resistance produces only a small deceleration, typically around 0.16 km/h/s.
Correct answer: 0.16 km phps- A. 0.3
- B. 0.26
- C. 0.225
- D. 0.16
Explanation: Wet rails reduce adhesion below the dry-rail value, so the coefficient must be less than 0.26; a commonly used wet-rail value is about…
Correct answer: 0.16