Induction and Synchronous Machines MCQs (Part-2)

What is the main function of the stator in an induction motor?

A To generate magnetic fields
B To produce mechanical power
C To supply excitation current
D To rotate with the rotor

What happens when the slip of an induction motor is 0?

A The rotor stops
B The motor operates at synchronous speed
C The motor generates maximum torque
D The rotor moves faster than the stator

Which of the following is the primary feature of a wound rotor in an induction motor?

A It has short-circuited windings
B It allows for external resistance to be added for speed control
C It is connected to a capacitor for starting
D It doesn’t require a power supply

What is the primary function of the slip rings in an induction motor?

A To supply current to the rotor windings
B To allow the rotor to rotate at synchronous speed
C To cool the rotor windings
D To regulate the motor’s torque

Which of the following factors affects the efficiency of an induction motor?

A Speed of the rotor
B Type of rotor construction
C Voltage applied to the motor
D Type of load

What does the term “synchronous speed” refer to in a synchronous motor?

A The speed at which the rotor rotates relative to the stator
B The speed at which the magnetic field rotates
C The speed at which the rotor accelerates
D The speed at which the motor is started

What is the common use of a synchronous motor?

A Household fans
B Precision timing applications
C High-efficiency air conditioning
D Variable-speed drives

How does the power factor of an induction motor affect its operation?

A It determines the voltage supplied to the motor
B It affects the current drawn by the motor
C It controls the speed of the motor
D It regulates the torque of the motor

What is the impact of increasing the load on an induction motor?

A The rotor speed decreases
B The motor runs at synchronous speed
C The power factor increases
D The slip decreases

What is the effect of harmonic currents on induction motors?

A They improve motor efficiency
B They reduce the motor’s lifespan
C They increase the power factor
D They eliminate the need for external cooling

What is the primary difference between single-phase and three-phase induction motors?

A Single-phase motors have higher efficiency
B Three-phase motors are more suitable for larger loads
C Single-phase motors require more maintenance
D Three-phase motors are simpler in construction

In a synchronous motor, what is the effect of under-excitation?

A It improves the power factor
B It leads to a lagging power factor
C It causes the motor to operate at higher speed
D It increases the motor’s efficiency

What is the primary role of cooling systems in electrical machines?

A To increase the efficiency of the machine
B To maintain the operating temperature within safe limits
C To reduce the wear and tear on mechanical parts
D To improve the motor’s power factor

Which of the following is the main reason for using laminated cores in induction motors?

A To reduce the mechanical weight of the motor
B To minimize eddy current losses
C To increase the core’s magnetic permeability
D To enhance the motor’s speed control

What is the key characteristic of a squirrel-cage rotor that contributes to its simplicity?

A It uses external brushes and slip rings
B It has a solid rotor core without windings
C It requires a field winding for excitation
D It uses permanent magnets

What is the effect of high slip in an induction motor?

A The motor runs more efficiently
B The torque increases
C The motor operates at synchronous speed
D The rotor produces little power

Which of the following is an important consideration in the design of insulation materials for electrical machines?

A The motor’s weight
B The thermal conductivity of the material
C The cost of the material
D The motor’s speed rating

What is the primary role of an excitation system in synchronous machines?

A To provide cooling for the rotor
B To generate the magnetic field for the rotor
C To supply power to the stator windings
D To regulate the motor’s speed

What is the effect of increasing the number of poles in a synchronous motor?

A The motor speed increases
B The motor speed decreases
C The motor consumes more power
D The motor requires more excitation

In an induction motor, what is the typical behavior of the motor’s power factor under no-load conditions?

A The power factor is high
B The power factor is low
C The power factor is constant
D The power factor is not measurable