Motors Book - Chapter 8

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Motors Book Quizzes & Trivia

Questions and Answers
  • 1. 

    In many cases, a single-phase motor is constructed with both a start and a ___ winding in the stator.

    • A.

      Run

    • B.

      Stop

    • C.

      Shut-down

    • D.

      None of the above

    Correct Answer
    A. Run
    Explanation
    A single-phase motor is constructed with both a start and a run winding in the stator. The start winding is used to provide the initial torque to start the motor, while the run winding is used to keep the motor running once it has started. Therefore, the correct answer is "run".

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  • 2. 

    ___ is the lack of rotation when the stator's field and the rotor's field are parallel to one another.

    • A.

      Parallel rotation

    • B.

      Overload rating

    • C.

      Non-adjustable-trip

    • D.

      Locked in step

    Correct Answer
    D. Locked in step
    Explanation
    Locked in step is the lack of rotation when the stator's field and the rotor's field are parallel to one another. This means that the magnetic fields of the stator and rotor are aligned and unable to generate the necessary torque to initiate rotation. As a result, the motor remains stationary and does not rotate.

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  • 3. 

    Shaded-pole motors are commonly ___ HP or less and have low starting torque.

    • A.

      1/20

    • B.

      1/2

    • C.

      10

    • D.

      100

    Correct Answer
    A. 1/20
    Explanation
    Shaded-pole motors are commonly 1/20 HP or less and have low starting torque. This means that they are typically used for small applications that require low power and do not require a lot of force to start. Shaded-pole motors are simple and inexpensive, making them suitable for tasks such as powering fans, small appliances, and some types of pumps. The fact that they have low starting torque means that they may take longer to reach their full operating speed compared to motors with higher starting torque.

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  • 4. 

    The function of the ___ is to delay the magnetic flux in the area of the pole that is shaded.

    • A.

      Salient pole

    • B.

      Three-pole rheostat

    • C.

      Shaded pole

    • D.

      Pole-face windings

    Correct Answer
    C. Shaded pole
    Explanation
    The shaded pole is a type of pole used in electric motors. It consists of a small portion of the pole being shaded by a copper coil. This shading causes a time delay in the magnetic flux in that area, which creates a rotating magnetic field. This rotating field helps to start the motor and provides the necessary torque to keep it running. Therefore, the function of the shaded pole is to delay the magnetic flux in the area of the pole that is shaded.

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  • 5. 

    ___ control of shaded-pole motors is accomplished by adding windings in series with the main winding.

    • A.

      Reverse speed

    • B.

      Speed

    • C.

      Magnetic

    • D.

      Electromagnetic

    Correct Answer
    B. Speed
    Explanation
    The correct answer is "Speed" because adding windings in series with the main winding in shaded-pole motors allows for control over the motor's speed. The additional windings create a magnetic field that interacts with the main winding, causing a phase shift and resulting in a change in the motor's speed. By adjusting the current flowing through the windings, the speed of the motor can be increased or decreased.

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  • 6. 

    ___ is the opposition to the flow of AC in a circuit due to inductance.

    • A.

      Flux density

    • B.

      Inductive reactance

    • C.

      Hysteresis

    • D.

      Magnetic flux

    Correct Answer
    B. Inductive reactance
    Explanation
    Inductive reactance is the opposition to the flow of AC in a circuit due to inductance. Inductance is a property of an electrical circuit that causes a change in current to induce a voltage in the circuit. This voltage opposes the change in current, resulting in the opposition to the flow of AC. Therefore, inductive reactance is the correct answer as it directly relates to the opposition to the flow of AC due to inductance.

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  • 7. 

    When the motor reaches approximately ___% of full speed, the centrifugal switch opens, disconnecting the start winding from the circuit.

    • A.

      15

    • B.

      45

    • C.

      75

    • D.

      95

    Correct Answer
    C. 75
    Explanation
    When the motor reaches approximately 75% of full speed, the centrifugal switch opens, disconnecting the start winding from the circuit. This is because the centrifugal switch is designed to disconnect the start winding once the motor has reached a certain speed. By disconnecting the start winding, the motor can continue running using only the run winding, which is more efficient for normal operation.

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  • 8. 

    The speed at which a split-phase motor runs is determined by the number of ___ in the motor and the frequency of the supply voltage.

    • A.

      Poles

    • B.

      Windings

    • C.

      Rotors

    • D.

      Brushes

    Correct Answer
    A. Poles
    Explanation
    The speed at which a split-phase motor runs is determined by the number of poles in the motor and the frequency of the supply voltage. The poles in a motor are the electromagnets that create the magnetic field necessary for the motor to operate. The number of poles determines the speed at which the motor rotates. The frequency of the supply voltage, typically measured in Hertz, also affects the motor speed. So, the correct answer is "poles."

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  • 9. 

    A ___ motor is a single-phase motor with a capacitor connected in series with the start windings to produce phase displacement in the start winding.

    • A.

      Wound-rotor

    • B.

      Series

    • C.

      Design

    • D.

      Capacitor

    Correct Answer
    D. Capacitor
    Explanation
    A capacitor motor is a single-phase motor that uses a capacitor connected in series with the start windings. This capacitor helps to create a phase displacement in the start windings, which is necessary for the motor to start and run efficiently. By introducing this phase displacement, the capacitor motor is able to generate a rotating magnetic field, enabling it to start and operate smoothly.

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  • 10. 

    A ___ motor has one-capacitor in series with the start winding and one capacitor in series with the run windings.

    • A.

      Capacitor-run

    • B.

      Capacitor start-and-run

    • C.

      Shunt

    • D.

      Single-phase

    Correct Answer
    B. Capacitor start-and-run
    Explanation
    A capacitor start-and-run motor has one capacitor in series with the start winding and one capacitor in series with the run windings. This type of motor is commonly used in applications where high starting torque is required, such as in air conditioning units or refrigerators. The start capacitor provides the initial boost needed to overcome the inertia of the motor and start it rotating, while the run capacitor helps to maintain a steady speed once the motor is running. This configuration allows for efficient operation and improved performance of the motor.

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  • 11. 

    A ___ motor is commonly wound to run on either six or eight poles.

    • A.

      Multispeed, single-phase

    • B.

      Single-speed, split-phase

    • C.

      Two-speed, split-phase

    • D.

      Multispeed, three-phase

    Correct Answer
    C. Two-speed, split-phase
    Explanation
    A two-speed, split-phase motor is commonly wound to run on either six or eight poles. This type of motor has two different speeds that can be selected, and it uses a split-phase design, which means it has two separate windings. The motor can be wired in a way that allows it to run on either six or eight poles, depending on the desired speed.

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  • 12. 

    A capacitor-start motor operates much the same as a split-phase motor, in that it uses a centrifugal switch that opens at approximately ___% to ___% of full-load speed.

    • A.

      20; 40

    • B.

      40; 60

    • C.

      60; 80

    • D.

      80; 100

    Correct Answer
    C. 60; 80
    Explanation
    A capacitor-start motor operates much the same as a split-phase motor, in that it uses a centrifugal switch that opens at approximately 60% to 80% of full-load speed.

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  • 13. 

    For a shaded-pole motor, the stator has two or more ___ poles that are divided into parts.

    • A.

      Salient

    • B.

      Shaded

    • C.

      Rotor

    • D.

      Magnetic

    Correct Answer
    A. Salient
    Explanation
    A shaded-pole motor is a type of single-phase induction motor. In this motor, the stator has salient poles that are divided into parts. These divided parts create shading coils, which are responsible for producing a rotating magnetic field. The shaded-pole motor is named after these shading coils, which help to start the motor and provide a rotating magnetic field without the need for a separate starting winding.

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  • 14. 

    In a capacitor-run motor the addition of a second ___ creates a three-speed version of the motor.

    • A.

      Soft starter

    • B.

      Plug fuse

    • C.

      Brush

    • D.

      Auxiliary winding

    Correct Answer
    D. Auxiliary winding
    Explanation
    In a capacitor-run motor, the addition of a second auxiliary winding creates a three-speed version of the motor. The auxiliary winding, when connected in parallel with the main winding, provides an additional magnetic field that allows the motor to operate at different speeds. By switching between the main winding and the auxiliary winding, the motor can be set to run at different speeds, providing versatility and flexibility in its applications.

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  • 15. 

    Capacitor start-and-run motors are typically used to run ___ and ___.

    • A.

      Fans; blowers

    • B.

      Refrigerators; air compressors

    • C.

      Air conditioners; power tools

    • D.

      All of the above

    Correct Answer
    B. Refrigerators; air compressors
    Explanation
    Capacitor start-and-run motors are typically used to run refrigerators and air compressors. These motors are designed to provide the initial torque needed to start the motor and then switch to a run capacitor to maintain a steady speed during operation. Refrigerators require a motor to run the compressor, which circulates refrigerant and keeps the food cold. Air compressors use a motor to power the pump, which pressurizes air for various applications. Therefore, the correct answer is refrigerators; air compressors.

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