Induction and Synchronous Machines MCQs (Part-1)

What is the main principle of operation of an induction motor?

A Electromagnetic induction
B Mutual induction
C Electromagnetic radiation
D Electrostatic induction

What is the primary function of a rotor in an induction motor?

A To produce the rotating magnetic field
B To provide mechanical power output
C To convert electrical energy to magnetic energy
D To store electrical energy

Which of the following is a characteristic of a squirrel-cage rotor?

A It uses external brushes for electrical connection
B It consists of copper or aluminum bars short-circuited by end rings
C It requires slip rings for starting
D It has wound windings

What is the term for the difference between synchronous speed and rotor speed in an induction motor?

A Slip
B Torque
C Efficiency
D Power factor

What is the synchronous speed of a motor in a three-phase system?

A The speed of the rotor
B The speed of the stator
C A constant speed determined by the number of poles and frequency
D A variable speed depending on load

Which of the following methods is commonly used to start an induction motor?

A Direct-on-line starting
B Star-delta starting
C Autotransformer starting
D All of the above

Which of the following is true about synchronous motors?

A They operate at a constant speed
B They have a variable speed
C They always require a mechanical starting device
D They are commonly used in low-power applications

What is the primary cause of core losses in an electrical machine?

A Resistance of the stator winding
B Hysteresis and eddy currents in the core material
C Leakage inductance
D Rotational friction

In which type of motor is the excitation system most crucial?

A Induction motor
B Synchronous motor
C Universal motor
D Permanent magnet motor

What does the power factor of a motor indicate?

A The amount of heat generated by the motor
B The efficiency of the motor in converting electrical to mechanical power
C The phase difference between voltage and current
D The maximum torque the motor can produce

Which of the following components is used for voltage regulation in synchronous motors?

A Capacitor bank
B Excitation system
C Inductor
D Rectifier

What is the main advantage of using a wound rotor in an induction motor?

A It provides higher efficiency
B It allows for external resistance to be added for speed control
C It requires less maintenance
D It operates at a lower temperature

What is the purpose of the air gap in an induction motor?

A To provide insulation between the rotor and stator
B To enable magnetic flux to pass between the stator and rotor
C To allow for cooling of the motor components
D To reduce mechanical wear

What is the typical cooling method used for large synchronous motors?

A Air cooling
B Water cooling
C Oil cooling
D Hybrid cooling

What is the main effect of harmonics in electrical machines?

A They reduce the efficiency of the motor
B They cause mechanical vibrations and noise
C They increase the operating temperature
D All of the above

Which type of motor is best suited for applications requiring constant speed under varying load?

A Induction motor
B Synchronous motor
C Universal motor
D DC motor

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

A Three-phase motors are more efficient
B Single-phase motors require external starting mechanisms
C Three-phase motors have a constant magnetic field
D All of the above

What is the purpose of the stator in a synchronous motor?

A To provide excitation current
B To produce a rotating magnetic field
C To generate mechanical torque
D To regulate the motor’s speed

Which of the following is a disadvantage of induction motors?

A They are not self-starting
B They have low efficiency at light loads
C They require external excitation
D They are difficult to maintain

What is a common application of synchronous motors?

A Air conditioning compressors
B Large industrial compressors
C Power factor correction in power systems
D Household appliances