Electrical Machines (Part-4)

What type of energy conversion occurs in a generator?

A Electrical to mechanical
B Mechanical to electrical
C Electrical to heat
D Mechanical to thermal

What is the stationary part of an induction motor called?

A Rotor
B Armature
C Stator
D Commutator

What is the main function of a slip ring in an AC generator?

A To transfer current to or from the rotating coil
B To rectify AC to DC
C To reduce resistance
D To increase torque

What is the frequency of the induced EMF in the rotor of a squirrel cage induction motor at synchronous speed?

A Zero
B Equal to the supply frequency
C Half of the supply frequency
D Twice the supply frequency

Which type of motor is commonly used for conveyor belts?

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

What is the primary cause of copper losses in electrical machines?

A Resistance in the windings
B Hysteresis in the core
C Eddy currents in the core
D Magnetic flux leakage

What is the primary role of a capacitor in single-phase motors?

A To increase power output
B To create a phase shift for starting torque
C To reduce losses
D To provide insulation

What does the term “core saturation” refer to in electrical machines?

A Increased slip in the rotor
B Magnetic core operating at maximum flux density
C Loss of rotor alignment
D Overheating of the windings

What is the main advantage of using a brushless motor?

A Higher starting torque
B Less maintenance and longer lifespan
C Simplified construction
D Reduced manufacturing cost

What determines the torque produced by an induction motor?

A Voltage applied to the stator
B Rotor material
C Interaction between rotor current and stator magnetic field
D Size of the stator core

What happens to the speed of a DC motor when load increases?

A Increases
B Decreases
C Remains constant
D Becomes zero

What is the primary function of laminating the core of a transformer?

A To reduce eddy current losses
B To improve cooling efficiency
C To reduce core weight
D To improve voltage regulation

What is the main characteristic of a stepper motor?

A Rotates in discrete steps
B Operates at synchronous speed
C Produces high starting torque
D Requires brushes for operation

What does a flywheel help maintain in electrical machines?

A Low power consumption
B Smooth rotational motion
C Reduced current losses
D Stable voltage

Which part of a synchronous motor determines the rotor speed?

A Supply frequency
B Load torque
C Rotor resistance
D Stator winding

What is the function of commutators in DC machines?

A To ensure unidirectional current flow
B To reduce core losses
C To step up voltage
D To control slip

Why are ball bearings used in electrical machines?

A To reduce electrical losses
B To minimize mechanical friction
C To increase magnetic flux
D To maintain constant speed

What is the primary purpose of insulation in electrical machines?

A To prevent electrical leakage
B To increase current
C To regulate speed
D To improve magnetic field strength

Which loss is directly proportional to the square of the load current?

A Core loss
B Copper loss
C Friction loss
D Windage loss

What is the typical cooling method for large electrical machines?

A Natural convection
B Forced air or liquid cooling
C Radiation
D Thermoelectric cooling