All Free Electrical Engineering MCQs with Answers

• A. the control action depends on the size of the system
• B. the control action depends on system variables
• C. the control action depends on the input signal
• D. the control action is independent of the output

Explanation: In an open-loop system, the controller does not measure or use the output, so its control action is independent of output feedback.

• A. Closed loop system
• B. Semiclosed loop system
• C. Open system
• D. None of the above

Explanation: A closed-loop system feeds the output back for comparison with the reference input, so the control action depends on the output.

• A. Field controlled D.C. motor
• B. Ward leonard control
• C. Metadyne
• D. Stroboscope

Explanation: A field-controlled DC motor can be operated in open loop by setting its field current without measuring the resulting speed.

• A. Open loop system
• B. Closed loop system
• C. Both A. and B.
• D. Neither A. nor B.

Explanation: Closed-loop systems can oscillate when feedback introduces excessive phase shift or insufficient stability margin.

• A. Transient response
• B. Error response
• C. Dynamic response
• D. Either of the above

Explanation: The initial part of a system response, before the output settles to its final value, is the transient response.

• A. good stability
• B. slow response
• C. good accuracy
• D. sufficient power handling capacity

Explanation: A good control system should respond quickly while maintaining stability, accuracy, and adequate power capability.

• A. fluctuating loads
• B. variable speed loads
• C. low torque loads
• D. power factor corrections

Explanation: An overexcited synchronous motor draws leading current, which supplies leading reactive power and improves a lagging system power factor.

• A. back e.m.f. is less than the applied voltage
• B. back e.m.f. is equal to the applied voltage
• C. back e.m.f. of rotor is more than the applied voltage
• D. none of the above

Explanation: Regenerative braking occurs when the motor operates as a generator and returns power to the supply, requiring its generated back EMF to…

• A. inlet pressure increase
• B. speed shoots up
• C. exhaust gets choked
• D. steam flow gets clogged

Explanation: A turbine is tripped by an overspeed protection system when its speed rises dangerously, preventing mechanical damage.

• A. carbon brushes
• B. coil
• C. commutator
• D. magnetic field

Explanation: A DC generator uses a split-ring commutator to rectify the internally generated AC, whereas an AC generator generally uses slip rings to…

• A. Retaintivity
• B. Permeability
• C. Flux
• D. Hysteresis

Explanation: Hysteresis is the lag of magnetization or flux density behind the changing magnetizing field.

• A. Maximum
• B. Zero
• C. Intermediate values
• D. No back emf

Explanation: For a DC motor, back emf is proportional to speed, E_b = kΦω. Therefore, when speed is maximum under normal operating conditions, the back…

• A. A torque about horizontal axis
• B. A torque about vertical axis
• C. An upward force along the axis
• D. No resultant force

Explanation: Opposite currents make the coaxial coils repel, but with the small coil exactly concentric and centered, the forces on opposite sides…

• A. Magnetic flux density
• B. Torque
• C. Mutual induction
• D. Motional emf

Explanation: The motional emf is e = Blv when the conductor, velocity, and magnetic field are mutually perpendicular.

• A. Small output
• B. Eddy currents and magnetic hysterias
• C. Soft iron core
• D. Back emf

Explanation: Transformer losses include core losses from hysteresis and eddy currents, as well as copper loss in the windings.

• A. number of turns in the coil
• B. magnetic field strength
• C. frequency of rotation
• D. all of above

Explanation: For an AC dynamo, generated emf is proportional to the number of turns, magnetic flux or field strength, and rotational speed or…

• A. water pumps
• B. jaw crushers
• C. centrifugal blowers
• D. none of the aboveGet Study Guides

Explanation: A belted slip-ring induction motor provides high starting torque with controlled starting current, making it suitable for heavy-load…

• A. 20 to 30 m/s
• B. 10 to 15 m/s
• C. 5 to 10 m/s
• D. 1 to 2.5 m/sCompare Power Rates

Explanation: Crane travelling mechanisms normally move at about 1 to 2.5 m/s, allowing controlled positioning of suspended loads.

• A. horsepower rating increases but r.p.m. decreases
• B. horsepower rating decreases but r.p.m. increases
• C. horsepower rating and operating speed increases
• D. horsepower rating and operating speed decreases

Explanation: An induction motor becomes more expensive when its horsepower increases and its speed decreases, because the lower-speed motor requires a…

• A. Type of bearings
• B. Type of enclosure
• C. Noise
• D. Arrangement for power transmis¬sion
• E. None of the above

Explanation: Low noise is especially important in air conditioners because the motor operates near occupied spaces and often runs for long periods.