Electrical Machines (Part-3)

What is the main function of a motor?

A To store electrical energy
B To convert electrical energy into mechanical energy
C To regulate voltage
D To generate electricity

Which component of a transformer prevents flux leakage?

A Core
B Stator
C Rotor
D Windings

What does “rotor” refer to in an electrical machine?

A Stationary magnetic part
B Rotating part of the machine
C The winding for generating voltage
D The frame for supporting the machine

What is the synchronous speed of a machine dependent on?

A Resistance of windings
B Supply frequency and number of poles
C Rotor mass
D Core material

What is the purpose of a starter in a motor?

A To limit the initial current
B To increase speed
C To reduce torque
D To maintain constant temperature

Which loss is caused by alternating magnetization of the core?

A Friction loss
B Copper loss
C Hysteresis loss
D Eddy current loss

Which material is commonly used for the core of electrical machines?

A Aluminum
B Silicon steel
C Copper
D Carbon

What does an increase in slip in an induction motor indicate?

A Increased speed
B Decreased rotor speed
C Improved efficiency
D Reduced torque

What is the main advantage of a three-phase motor over a single-phase motor?

A Higher efficiency and smoother operation
B Easier starting without additional components
C Lower weight for the same power rating
D Less complex construction

What is the main characteristic of a synchronous generator?

A Produces DC power
B Operates without excitation
C Operates at constant speed regardless of load
D Produces variable voltage

What causes eddy current losses in electrical machines?

A Improper insulation
B Circulating currents in the core
C Friction between moving parts
D High-frequency operation

What is the role of bearings in electrical machines?

A To generate power
B To control magnetic flux
C To support the rotating shaft
D To increase voltage

What is the main advantage of brushless motors?

A Low torque output
B Low-speed operation
C Maintenance-free design
D Simple control mechanism

What is the purpose of a flywheel in electrical machines?

A To store rotational energy
B To reduce slip
C To step up voltage
D To improve insulation

Which part of a DC motor experiences commutation?

A Stator
B Field winding
C Armature winding
D Core

Why are permanent magnets used in some motors?

A To control speed
B To reduce resistance
C To provide a fixed magnetic field
D To improve cooling

What is the primary function of field winding in a synchronous machine?

A To produce the main magnetic field
B To reduce vibrations
C To increase speed
D To improve cooling efficiency

What type of cooling is used in high-power electrical machines?

A Natural air cooling
B Forced air or liquid cooling
C Radiation cooling
D Magnetic cooling

Which of the following is an essential step in electrical machine maintenance?

A Increasing speed periodically
B Reducing power supply voltage
C Inspecting insulation and connections
D Operating the machine without load

Which type of motor is commonly used in computer hard drives?

A Stepper motor
B Brushless DC motor
C Universal motor
D Induction motor