All Free Electrical Engineering MCQs with Answers

• A. equal to full load current
• B. less than full load current
• C. slightly more than full load current
• D. several times the full load current

Explanation: A shaded-pole motor has relatively high leakage impedance, which limits its locked-rotor current; it is therefore only slightly greater…

• A. It requires more maintenance of commutator and other mechanical devices
• B. It makes quite a bit of noise on starting
• C. In fractional horse power motors, it has replaced the capacitor motors
• D. It is not easily reversed

Explanation: Repulsion-start induction motors have high starting torque but require commutator maintenance, produce noise, and are difficult to…

• A. running winding
• B. rotor winding
• C. field winding
• D. compensating winding

Explanation: The starting winding is used only to create the initial rotating-field effect and is disconnected after the motor accelerates.

• A. smaller brush width
• B. less number of field turns
• C. more number of armature turns
• D. less air gap
• E. all of the above

Explanation: An AC series motor uses fewer field turns, more armature turns, a smaller air gap, and narrower brushes than a comparable DC series motor…

• A. it revolves synchronously
• B. it is not subject to any magnetic or mechanical vibrations
• C. it can be easily manufactured in extremely small sizes of up to 1 W output
• D. it develops hysteresis torque which is extremely steady both in amplitude and phase

Explanation: A hysteresis motor produces a nearly constant hysteresis torque, steady in both magnitude and phase, while running synchronously.

• A. It requires only one winding
• B. It can rotate in one direction only
• C. It is self-starting
• D. It is not self-starting

Explanation: A single-phase induction motor has a pulsating rather than rotating starting field, so its starting torque is zero.

• A. varying field flux with tapped field windings
• B. connecting rheostat in series
• C. applying variable voltage by means of silicon controlled rectifier
• D. applying variable voltage by means of variable auto-transformer
• E. all of the above methods

Explanation: Universal-motor speed can be controlled by changing field flux, adding series resistance, or varying the applied voltage using an SCR or…

• A. It is extremely sensitive to fluctuations in supply voltage
• B. Its high starting torque is due to its high rotor hysteresis loss
• C. It is extremely quiet in operation
• D. It accelerates from rest to full-speed almost instantaneously

Explanation: A hysteresis motor is relatively insensitive to supply-voltage fluctuations, while its hysteresis torque gives smooth and rapid…

• A. armature
• B. field
• C. rotor
• D. stator

Explanation: In a single-phase induction motor, the starting winding is an auxiliary stator winding placed 90 electrical degrees from the main winding.

• A. gearing
• B. belts
• C. brakes
• D. chains

Explanation: A universal motor runs at very high speed, so a gear train is commonly used to reduce speed and increase the available torque.

• A. Split phase motor
• B. Universal motor
• C. Hysteresis motor
• D. Shaded pole motor

Explanation: The hysteresis motor has a smooth, non-toothed rotor and produces nearly uniform torque, so it operates with exceptionally low mechanical…

• A. fans
• B. blowers
• C. sound equipment
• D. mixer grinders

Explanation: The quiet, vibration-free operation of a hysteresis motor makes it suitable for sound equipment, record players and similar precision…

• A. armature winding
• B. field winding
• C. either armature winding or field winding
• D. none of the above

Explanation: Reversing either the armature-current direction or the field-current direction reverses the torque, because torque depends on the…

• A. high inductance of field and armature circuits
• B. induced current in rotor due to variations of flux
• C. fine copper wire winding
• D. none of the above

Explanation: When a DC series motor operates on AC, its field and armature windings have substantial inductive reactance, causing a large lagging…

• A. Split phase motor
• B. Reluctance motor
• C. Hysteresis motor
• D. Universal motor

Explanation: A hysteresis motor uses a smooth cylindrical rotor made of hard magnetic material, with no rotor teeth, slots or electrical winding.

• A. gear trains
• B. V-belts
• C. brakes
• D. chains

Explanation: A gear train reduces the output speed while allowing the universal motor to continue operating at its efficient high speed.

• A. Universal motor
• B. Repulsion motor
• C. Capacitor motor
• D. All single phase motors have zero starting torque

Explanation: A capacitor-run motor, often loosely called a capacitor motor, has relatively poor starting torque because its small running capacitor…

• A. Capacitor run motor
• B. Shaded pole motor
• C. Hysteresis motor
• D. Schrage motor

Explanation: The Schrage motor permits control of its power factor through injected voltage, so it can be operated at approximately unity power factor.

• A. Gradually varying load
• B. Non-reversing, no-load start
• C. Reversing, light start
• D. Reversing, heavy start

Explanation: Cranes and hoists frequently start with heavy loads and must reverse direction for lifting and lowering operations.

• A. 200 to 250 W
• B. 250 to 500 W
• C. 50 to 150 W
• D. 10 to 20 W

Explanation: Domestic ceiling fans use small motors, commonly rated roughly from 50 to 150 W depending on fan size and design.