Free Electrical Machines MCQs with Answers
1,061 Electrical Machines MCQs from Electrical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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- A. 40 Hz
- B. 25 Hz
- C. 16 Hz
- D. non of these
Explanation: Low-frequency railway traction commonly uses 16⅔ Hz or 25 Hz, while 40 Hz is not a standard common frequency for such systems.
Correct answer: 40 Hz- A. has better coefficient of adhesion
- B. are suited both for passanger as well as freight service
- C. has better riding qualities due to the reduction of lateral forces
- D. has all above qualities
Explanation: Monomotor bogies can provide good adhesion, serve both passenger and freight duties, and improve riding by reducing lateral forces.
Correct answer: has all above qualities- A. Retardation and acceleration values
- B. Gradient
- C. Distance between stops
- D. All of the above
Explanation: Specific energy consumption depends on acceleration and retardation, gradients, and the distance between stops.
Correct answer: All of the above- A. main line
- B. urban
- C. suburban
Explanation: Main-line trains travel longer distances with fewer stops, so less energy is spent on repeated acceleration and braking per…
Correct answer: main line- A. Work against the resistance to motion
- B. Work against gravity while moving up the gradient
- C. Acceleration
- D. All of the above
Explanation: Propelling energy must overcome rolling and air resistance, raise the train against gravity on gradients, and accelerate its mass.
Correct answer: All of the above- A. easy speed control
- B. high starting tractive effort
- C. equipment capable of with standing large temporary loads
- D. all of the above
Explanation: A good traction system needs controllable speed, high starting tractive effort for overcoming train inertia, and equipment that tolerates…
Correct answer: all of the above- A. wheel base of axles is more
- B. degree of curvature is more
- C. both A. and B.
- D. none of the above
Explanation: A longer rigid wheelbase causes greater geometric difficulty on a curve, while a sharper curve increases the difference in wheel travel…
Correct answer: both A. and B.- A. Diesel shunters
- B. Steam locomotives
- C. Electric locomotives
- D. Diesel locomotives
Explanation: Steam locomotives contain large reciprocating masses whose inertia produces substantial unbalanced forces, especially at changing speeds.
Correct answer: Steam locomotives- A. main-line service
- B. urban service
- C. sub-urban service
- D. all of the above
Explanation: Main-line trains run between widely spaced stations, so they spend relatively long periods running freely or coasting after acceleration.
Correct answer: main-line service- A. neutral wire
- B. rails
- C. cables
- D. common earthing
Explanation: In the usual tramway single-wire system, the overhead conductor supplies current and the running rails carry the return current to the…
Correct answer: rails- A. Less current drain on the heavy load torque
- B. Current surges after temporary switching off supply
- C. Self relieving property
- D. Commutating property at heavy load
Explanation: After a temporary supply interruption, the series-field flux collapses while the train is still moving; restoration can then produce a…
Correct answer: Current surges after temporary switching off supply- A. resistance offered by air
- B. friction at the track
- C. friction at various parts of the rolling stock
- D. all of the above
Explanation: Train resistance includes air resistance, friction and rolling resistance at the wheel-track interface, and friction in bearings and other…
Correct answer: all of the above- A. steel mills
- B. power stations
- C. narrow gauge traction
- D. factories for material transportation
Explanation: Battery-operated trucks are mainly used inside factories and warehouses to transport materials over short distances.
Correct answer: factories for material transportation- A. Vacuum pump
- B. Ejector
- C. Any of the above
- D. None of the above
Explanation: Both a vacuum pump and an ejector can produce a region of low pressure called a vacuum.
Correct answer: Any of the above- A. Plugging braking
- B. Rheostatic braking
- C. Regenerative braking
- D. None of the above
Explanation: Plugging applies a reverse torque by reversing the motor connections, producing rapid braking and bringing the locomotive to a dead stop.
Correct answer: Plugging braking- A. 12 V
- B. 24 V
- C. 220 V
- D. 600 to 750 V
Explanation: D.C. suburban railway systems commonly use a third-rail or overhead supply in the range of 600 to 750 V.
Correct answer: 600 to 750 V- A. more on steeper gradient
- B. more with high train resistance
- C. less if distance between stops is more
- D. all of the above
Explanation: Energy consumption rises with steeper gradients and greater train resistance, while longer distances between stops reduce repeated…
Correct answer: all of the above- A. greased
- B. wet
- C. sprayed with oil
- D. cleaned with sand
Explanation: Sand removes moisture and increases friction between the wheel and rail, raising the coefficient of adhesion.
Correct answer: cleaned with sand- A. Cascade control
- B. Pole changing
- C. Rheostat control
- D. Combination of cascade and pole changing
Explanation: Rheostat or rotor-resistance control wastes substantial power as heat in the external resistance, so its efficiency is low.
Correct answer: Rheostat control- A. distance between the stops is more
- B. maximum speed reached is high
- C. acceleration and retardation rates are low
- D. all of the above
Explanation: Main-line trains have widely spaced stops, allowing higher speeds, while their acceleration and retardation rates are lower than those…
Correct answer: all of the above