Electrical Machines (Part-8)

What is the primary role of an electrical machine?

A To store energy
B To convert energy from one form to another
C To transfer power without losses
D To increase current

What does the armature winding in a DC machine do?

A Creates the magnetic field
B Generates or carries the main current
C Reduces friction
D Steps up voltage

What is the purpose of a commutator in a DC machine?

A To convert AC generated in the armature into DC
B To generate magnetic flux
C To reduce losses
D To step up current

What determines the synchronous speed of a machine?

A Frequency of supply and the number of poles
B Resistance of the rotor
C Core material
D Type of winding

What is the main loss reduced by laminating the core of electrical machines?

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

Why is the rotor of an induction motor not at synchronous speed?

A To allow induction of current in the rotor
B To reduce losses
C To create a uniform magnetic field
D To prevent overheating

What does slip in an induction motor indicate?

A The speed of the motor
B The difference between synchronous speed and rotor speed
C The power factor of the motor
D The load on the motor

What is the primary purpose of field windings in electrical machines?

A To produce the magnetic field
B To carry current
C To insulate the core
D To reduce losses

What is the function of brushes in a DC motor?

A To transfer current to and from the rotating commutator
B To insulate the rotor
C To step up voltage
D To reduce torque

What type of current is induced in the rotor of an induction motor?

A Direct current
B Alternating current
C Pulsating current
D Constant current

Which component in a transformer minimizes magnetic flux leakage?

A Windings
B Core
C Oil
D Bushings

What is the typical power source for stepper motors?

A DC supply with pulses
B Pure AC
C Constant DC voltage
D High-frequency AC

What is the main purpose of excitation in synchronous machines?

A To supply the magnetic field
B To start the machine
C To increase speed
D To reduce losses

What is the primary cause of core losses?

A Copper resistance
B Hysteresis and eddy currents
C Friction in moving parts
D Improper insulation

What type of machine is used in elevators?

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

What is the main reason for using silicon steel in transformer cores?

A To reduce hysteresis losses
B To increase resistance
C To improve mechanical strength
D To enhance cooling

What does a flywheel in a machine help with?

A To store rotational energy and smooth speed fluctuations
B To step up torque
C To generate power
D To reduce heat

Which motor is most suitable for low-power appliances like mixers?

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

What is the main advantage of brushless motors?

A Longer lifespan due to no brushes
B Simpler construction
C Higher losses
D Low efficiency

Why are cooling systems necessary in electrical machines?

A To increase efficiency
B To dissipate heat and prevent overheating
C To improve insulation
D To improve power factor