AC Machines: Interactive Learning Quizzes for Electrical Engineering Students

Question 1

What primary purpose does slip serve in an asynchronous AC motor?

Accepted Answer

To provide initial torque for the motor to start

Answer

To regulate the motor's speed

Answer

To enhance the motor's efficiency

Answer

To reduce the motor's power factor

Question 2

Select the typical application for a synchronous generator:

Accepted Answer

Electricity generation in power plants

Answer

Electric vehicle propulsion

Answer

Industrial machinery operation

Answer

Domestic appliance usage

Question 3

An AC motor consists of the following components, except:

Accepted Answer

Commutator

Answer

Stator

Answer

Rotor

Answer

Capacitor

Question 4

A synchronous generator is characterized by:

Accepted Answer

Maintaining a constant speed

Answer

Varying its frequency

Answer

Being self-starting

Answer

Exhibiting low efficiency

Question 5

The primary distinction between a squirrel-cage rotor and a wound rotor in an induction motor lies in their:

Accepted Answer

Construction: squirrel-cage has bars and end rings, wound has coils and slots

Answer

Starting torque: squirrel-cage has lower, wound has higher

Answer

Efficiency: squirrel-cage is more efficient, wound is less efficient

Answer

Application: squirrel-cage for small motors, wound for large motors

Question 6

In a wound rotor induction motor, slip rings serve the primary purpose of:

Accepted Answer

Establishing electrical connection to the rotor windings

Answer

Reducing the starting current

Answer

Enhancing overall efficiency

Answer

Controlling the motor's speed

Question 7

Brushless alternators are categorized as:

Accepted Answer

Types of AC generators

Answer

Types of DC generators

Answer

Types of stepper motors

Answer

Types of synchronous motors

Question 8

In a synchronous generator, the prime mover rotates at a speed:

Accepted Answer

Identical to the synchronous speed

Answer

Slightly above the synchronous speed

Answer

Slightly below the synchronous speed

Answer

Independent of the synchronous speed

Question 9

Which of the following is not an example of an AC motor?

Accepted Answer

Brushless DC motor

Answer

Induction motor

Answer

Synchronous motor

Answer

Stepper motor

Question 10

The power factor of a purely inductive load is:

Accepted Answer

Less than 1

Answer

Greater than 1

Answer

Equal to 1

Answer

Zero

Question 11

Which of the following is not a characteristic of a stepper motor?

Accepted Answer

Closed-loop control

Answer

Precise positioning

Answer

High torque at low speeds

Answer

Brushless construction

Question 12

The armature of a DC generator is typically made of:

Accepted Answer

Laminated steel

Answer

Solid steel

Answer

Copper

Answer

Aluminium

Question 13

The efficiency of an AC machine is typically calculated using the:

Accepted Answer

Ratio of output power to input power

Answer

Input power

Answer

Output power

Answer

Difference between input and output power

Question 14

Which type of AC motor relies on the principle of electromagnetic induction to generate torque?

Accepted Answer

Asynchronous motor (induction motor)

Answer

Synchronous motor

Answer

DC motor

Answer

Stepper motor

Question 15

What is the key difference between a synchronous motor and an asynchronous motor?

Accepted Answer

Synchronous motors run at the same speed as the rotating magnetic field, while asynchronous motors run slightly slower.

Answer

Asynchronous motors have a higher starting torque than synchronous motors.

Answer

Synchronous motors require a DC excitation source, while asynchronous motors do not.

Answer

Asynchronous motors are more efficient than synchronous motors.

Question 16

Which component in an AC generator converts mechanical energy into electrical energy?

Accepted Answer

Stator

Answer

Rotor

Answer

Armature

Answer

Field winding

Question 17

What is the relationship between the frequency of an AC generator and the number of poles on its rotor?

Accepted Answer

Frequency is directly proportional to the number of poles.

Answer

Frequency is inversely proportional to the number of poles.

Answer

Frequency is independent of the number of poles.

Answer

Frequency is proportional to the square root of the number of poles.

Question 18

What is the main advantage of using a transformer in an AC power system?

Accepted Answer

To change the voltage level of the AC signal

Answer

To isolate different parts of the system

Answer

To regulate the frequency of the AC signal

Answer

To convert AC to DC

Question 19

What is the difference between a step-up transformer and a step-down transformer?

Accepted Answer

A step-up transformer increases the voltage and decreases the current, while a step-down transformer decreases the voltage and increases the current.

Answer

A step-up transformer decreases the voltage and increases the current, while a step-down transformer increases the voltage and decreases the current.

Answer

Both step-up and step-down transformers perform the same function.

Answer

A step-up transformer has a higher turns ratio than a step-down transformer.

Question 20

What is the purpose of a laminated core in a transformer?

Accepted Answer

To reduce eddy current losses

Answer

To improve magnetic flux density

Answer

To increase the mechanical strength of the transformer

Answer

To prevent overheating

Question 21

What is the relationship between the power factor of an AC circuit and its efficiency?

Accepted Answer

A high power factor indicates a high efficiency.

Answer

A low power factor indicates a high efficiency.

Answer

Power factor has no impact on circuit efficiency.

Answer

A low power factor indicates a low efficiency.

Question 22

Which of the following is NOT a characteristic of a synchronous AC generator?

Accepted Answer

Variable speed

Answer

Constant frequency

Answer

Constant output voltage

Answer

Relies on a rotating magnetic field

Question 23

In an AC induction motor, what is the primary function of the stator?

Accepted Answer

To produce a rotating magnetic field

Answer

To generate an electric current

Answer

To adjust the speed of the motor

Answer

To convert AC to DC

Question 24

Which of the following is an advantage of using a squirrel-cage rotor in an AC induction motor?

Accepted Answer

Low maintenance requirement

Answer

Variable speed control

Answer

High starting torque

Answer

High efficiency

Question 25

What is the purpose of slip rings in an AC synchronous motor?

Accepted Answer

To connect the rotor to an external circuit

Answer

To generate a rotating magnetic field

Answer

To convert AC to DC

Answer

To regulate the speed of the motor

Question 26

What is the primary difference between a synchronous and an asynchronous AC motor?

Accepted Answer

Speed locking

Answer

Starting torque

Answer

Power factor

Answer

Efficiency

Question 27

What is the main purpose of a damper winding in an AC synchronous generator?

Accepted Answer

To dampen electrical oscillations

Answer

To control the speed of the generator

Answer

To boost the output voltage

Answer

To convert AC to DC

Question 28

What is the major distinction between the construction of a synchronous and an asynchronous AC motor?

Accepted Answer

Presence or absence of slip rings

Answer

Type of rotor

Answer

Number of poles