All Free Electrical Engineering MCQs with Answers

• A. Hysteresis motor
• B. Reluctance motor
• C. Capacitor-run motor
• D. Universal motor

Explanation: A hysteresis motor runs smoothly and quietly at nearly constant speed, making it suitable for tape-recorders, clocks, and other timing…

• A. magnetic relay
• B. thermal relay
• C. centrifugal switch
• D. none of the above

Explanation: Domestic refrigerator compressors commonly use a magnetic current relay to disconnect the starting winding after the motor accelerates.

• A. 30 to 40
• B. 70 to 80
• C. 80 to 90
• D. 100

Explanation: The centrifugal switch normally opens when the motor reaches approximately 70 to 80 percent of synchronous speed, removing the auxiliary…

• A. Induction motor
• B. Three-phase series motor
• C. Schrage motor
• D. Hysteresis motor

Explanation: A three-phase series motor has a characteristic suitable for applications in which the load torque rises with speed, such as traction-type…

• A. Hysteresis motor
• B. Schrage motor
• C. Universal motor
• D. Reluctance motor

Explanation: A Schrage motor can be designed to operate with approximately unity power factor while also providing speed control.

• A. brush axis is 45° electrical to field axis
• B. brush axis coincides with the field axis
• C. brush axis is 90° electrical to field axis
• D. both B. and (c)Electricity

Explanation: Repulsion torque varies with the sine of twice the angle between the brush and field axes, so it becomes zero when the axes coincide or…

• A. d.c. series motor
• B. shaded pole motor
• C. capacitor-start capacitor-run motor
• D. reluctance motor

Explanation: Compressors require high starting torque and then efficient, quiet continuous operation, which is provided by a capacitor-start…

• A. improves the efficiency
• B. helps the rotor teeth to remain under the stator teeth
• C. helps in reducing the tendency of the rotor teeth to remain under the stator teeth
• D. improves the power factor

Explanation: Rotor-slot skewing prevents rotor and stator teeth from remaining directly aligned, thereby reducing cogging, magnetic locking, noise, and…

• A. secondary winding surrounds the primary winding
• B. primary winding surrounds the secondary winding
• C. both are usual arrangements
• D. none of the above

Explanation: In the usual ceiling-fan capacitor-run motor arrangement, the auxiliary or secondary winding is placed around the main or primary winding.

• A. A.C. motor
• B. D.C. shunt motor
• C. D.C. series motor
• D. none of the above

Explanation: A universal motor is a series motor that can operate on either AC or DC, so its speed-load characteristic resembles that of a DC series…

• A. high starting torque
• B. low starting torque
• C. medium starting torque
• D. very high starting torque

Explanation: A shaded-pole motor develops only a weak rotating magnetic field because the shaded coil produces a small delayed flux.

• A. damage to the starting winding
• B. damage to the centrifugal switch
• C. overloading of running winding
• D. none of the above

Explanation: If the centrifugal switch remains closed, the starting winding stays energized after the motor has accelerated.

• A. shunt motor
• B. series motor
• C. compound motor
• D. separately excited motor

Explanation: A repulsion-induction motor combines high starting torque with better running speed regulation than a simple repulsion motor, giving a…

• A. thin wire placed at the top of the slots
• B. thin wire placed at the bottom of the slots
• C. thick wire placed at the bottom of the slots
• D. thick wire placed at the top of the" slots

Explanation: The main winding carries the running current, so it uses comparatively thick wire and is placed at the bottom of the slots.

• A. brush axis is at 45° electrical to the field axis
• B. brush axis coincides with the field axis
• C. brush axis is at 90° electrical to the field axis
• D. none of the above

Explanation: Repulsion-motor torque is proportional to the interaction of the relevant fluxes and is maximum when the brush axis is approximately 45…

• A. aluminium
• B. cast iron
• C. chrome steel
• D. copper

Explanation: The hysteresis rotor is made from hard magnetic material such as chrome steel, which has a wide hysteresis loop and retains magnetism.

• A. pulsating
• B. uniform
• C. none of the above
• D. nil

Explanation: At standstill, the forward and backward rotating field components produce equal and opposite torques, so their net starting torque is…

• A. friction
• B. varying the resistance
• C. tapping the field
• D. centrifugal mechanism

Explanation: A sewing-machine universal motor commonly controls speed by inserting variable resistance in series with the motor, reducing the applied…

• A. capacitor run motor
• B. hysteresis motor
• C. universal motor
• D. repulsion motor

Explanation: Portable drills need a compact motor with high starting torque and high speed, which are characteristic advantages of the universal motor.

• A. retentivity
• B. resistivity
• C. susceptibility
• D. none of the above

Explanation: The rotor of a hysteresis motor requires high retentivity so it retains magnetism and develops hysteresis torque as the rotating field…