Gibilisco - Electron Tubes

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| By BATANGMAGALING
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BATANGMAGALING
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Quizzes Created: 32 | Total Attempts: 47,404
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  • 1/20 Questions

    The control grid of a vacuum tube is the electrical counterpart of the

    • Source of a MOSFET.
    • Collector of a bipolar transistor.
    • Anode of a diode.
    • Gate of an FET.
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Gibilisco - Electron Tubes - Quiz

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  • 2. 

    A major difference between a triode tube and an N-channel FET is the fact that

    • Triodes work with lower signal voltages.

    • Triodes are more compact.

    • Triodes need higher power-supply voltages.

    • Triodes don’t need filaments.

    Correct Answer
    A. Triodes need higher power-supply voltages.
    Explanation
    Triodes need higher power-supply voltages compared to N-channel FETs. This is because triodes require a high voltage to operate and control the flow of current through the vacuum tube. In contrast, N-channel FETs operate using a lower voltage and are able to control the current flow through a semiconductor channel. Therefore, the higher power-supply voltage requirement is a major difference between triode tubes and N-channel FETs.

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  • 3. 

    In a tube with a directly heated cathode,

    • The filament is separate from the cathode.

    • The grid is connected to the filament.

    • The filament serves as the cathode.

    • There is no filament.

    Correct Answer
    A. The filament serves as the cathode.
    Explanation
    In a tube with a directly heated cathode, the filament serves as the cathode. This means that the filament itself is responsible for emitting the electrons necessary for the operation of the tube. The filament is heated directly, which causes it to release electrons and create an electron cloud around it. These electrons are then attracted to the positively charged anode, creating the desired flow of current within the tube.

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  • 4. 

    Which of the following is most suitable for measuring the intensity of dim light?

    • A triode gas-filled tube

    • A photomultiplier tube

    • An electrostatic CRT

    • An electromagnetic CRT

    Correct Answer
    A. A photomultiplier tube
    Explanation
    A photomultiplier tube is most suitable for measuring the intensity of dim light because it is designed to amplify very weak signals of light. It consists of a photocathode that converts photons into electrons, and a series of dynodes that multiply the number of electrons. This multiplication process allows the photomultiplier tube to detect and measure very low levels of light intensity, making it ideal for applications where the light is extremely faint or dim.

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  • 5. 

    A tube with three grids is called a

    • Triode.

    • Tetrode.

    • Pentode.

    • Hexode.

    Correct Answer
    A. Pentode.
    Explanation
    A tube with three grids is called a pentode. A pentode is a type of vacuum tube that has five elements or electrodes, including three grids. These grids are used to control the flow of electrons within the tube. The pentode configuration allows for better control and amplification of electrical signals compared to tubes with fewer grids.

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  • 6. 

    In a tube with a cold cathode,

    • The filament is separate from the cathode.

    • The grid is connected to the filament.

    • The filament serves as the cathode.

    • There is no filament.

    Correct Answer
    A. There is no filament.
    Explanation
    In a tube with a cold cathode, there is no filament. This means that the cathode does not require heating in order to emit electrons. Instead, the cathode is made of a material that can emit electrons at room temperature without the need for a filament. This type of cathode is commonly used in fluorescent lamps and other gas discharge tubes.

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  • 7. 

    In a dissector tube, the aperture size is directly related to the

    • Operating voltage.

    • Signal-to-noise ratio.

    • Response speed.

    • Image resolution.

    Correct Answer
    A. Image resolution.
    Explanation
    The aperture size in a dissector tube is directly related to the image resolution. A larger aperture allows more light to enter the tube, resulting in a higher resolution image. This is because a larger aperture captures more details and improves the clarity and sharpness of the image. Conversely, a smaller aperture restricts the amount of light entering the tube, resulting in a lower resolution image with less detail. Therefore, the size of the aperture directly affects the image resolution in a dissector tube.

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  • 8. 

    The electron gun in a CRT is another name for its

    • Cathode.

    • Anode.

    • Control grid.

    • Screen grid.

    Correct Answer
    A. Cathode.
    Explanation
    The electron gun in a CRT is responsible for emitting a stream of electrons. The cathode is the part of the electron gun where electrons are generated. It is negatively charged and acts as the source of electrons in the CRT. Therefore, the correct answer is cathode.

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  • 9. 

    A tube with four grids is called a

    • Triode.

    • Tetrode.

    • Pentode.

    • Hexode.

    Correct Answer
    A. Hexode.
  • 10. 

    In a Klystron, the electron-beam density varies as a result of

    • Amplitude modulation.

    • Pulse modulation.

    • Velocity modulation.

    • Frequency modulation.

    Correct Answer
    A. Velocity modulation.
    Explanation
    In a Klystron, the electron-beam density varies as a result of velocity modulation. This means that the velocity of the electrons in the beam is modulated, or changed, in order to vary the density of the beam. This modulation is used to control the output power of the Klystron, making it an important aspect of its operation.

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  • 11. 

    The plate in a tetrode tube is normally connected to

    • A positive dc power-supply voltage.

    • A negative dc power-supply voltage.

    • Electrical ground.

    • RF ground.

    Correct Answer
    A. A positive dc power-supply voltage.
    Explanation
    In a tetrode tube, the plate is normally connected to a positive dc power-supply voltage. This is because the plate is the anode of the tube and it needs to be at a higher potential than the cathode to allow for the flow of current. By connecting it to a positive voltage, a potential difference is created between the plate and the cathode, which enables the tube to function properly.

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  • 12. 

    The electron beam in an electrostatic CRT is bent by

    • Magnetic fields produced by current-carrying coils.

    • Electric fields produced by charged electrodes.

    • A variable voltage on the screen grid.

    • Visible light striking the electrodes.

    Correct Answer
    A. Electric fields produced by charged electrodes.
    Explanation
    The correct answer is electric fields produced by charged electrodes. In an electrostatic CRT, the electron beam is bent by electric fields created by charged electrodes. These electrodes have a positive or negative charge, which creates an electric field that can attract or repel the electrons in the beam, causing them to change direction. Magnetic fields produced by current-carrying coils are not responsible for bending the electron beam in an electrostatic CRT. A variable voltage on the screen grid and visible light striking the electrodes also do not play a role in bending the electron beam.

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  • 13. 

    The screen grid in a tetrode tube is normally connected to

    • A positive dc power-supply voltage.

    • A negative dc power-supply voltage.

    • Electrical ground.

    • RF ground.

    Correct Answer
    A. A positive dc power-supply voltage.
    Explanation
    In a tetrode tube, the screen grid is typically connected to a positive dc power-supply voltage. This is done to control the flow of electrons between the screen grid and the plate. By applying a positive voltage to the screen grid, it creates an electric field that repels electrons, preventing them from reaching the plate. This helps to improve the tube's performance and efficiency.

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  • 14. 

    A vidicon camera tube is noted for its

    • Poor signal-to-noise ratio.

    • Large size and heavy weight.

    • Slow response to image movement in dim light.

    • Excellent selectivity and electrical ruggedness.

    Correct Answer
    A. Slow response to image movement in dim light.
    Explanation
    A vidicon camera tube is known for its slow response to image movement in dim light. This means that when there is low light, the vidicon camera tube takes a longer time to capture and process the image, resulting in a slower response. This can lead to blurry or distorted images in low light conditions.

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  • 15. 

    Which factor is most significant in limiting the maximum frequency at which a tube canoperate?

    • The power-supply voltage

    • The capacitance among the electrodes

    • The physical size of the tube

    • The current passing through the filament

    Correct Answer
    A. The capacitance among the electrodes
    Explanation
    The capacitance among the electrodes is the most significant factor in limiting the maximum frequency at which a tube can operate. Capacitance is a measure of the ability of the electrodes to store electrical charge, and it affects the speed at which the tube can respond to changes in signal. Higher capacitance leads to slower response times and limits the maximum frequency that the tube can handle. Therefore, the capacitance among the electrodes plays a crucial role in determining the operational limits of the tube.

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  • 16. 

    In a tetrode tube, the charge carriers are

    • Free electrons, which pass among the electrodes.

    • Holes, which are conducted within the electrodes.

    • Holes or electrons, depending on whether the device is P type or N type.

    • Nuclei of whatever elemental gas happens to exist in the tube.

    Correct Answer
    A. Free electrons, which pass among the electrodes.
    Explanation
    In a tetrode tube, the charge carriers are free electrons, which pass among the electrodes. This is because tetrode tubes are vacuum tubes that have four electrodes - a cathode, a control grid, a screen grid, and a plate. The free electrons emitted by the cathode are attracted towards the plate, but their flow can be controlled by the voltage applied to the control grid. The free electrons move among the electrodes, allowing for the amplification and control of electrical signals within the tube.

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  • 17. 

    A grounded-grid RF power amplifier

    • Requires more driving power, for a given RF power output, than a grounded-cathode RF power amplifier.

    • Requires less driving power, for a given RF power output, than a grounded-cathode RF power amplifier.

    • Oscillates at a more stable frequency than a grounded-cathode RF power amplifier.

    • Oscillates at a less stable frequency than a grounded-cathode RF power amplifier.

    Correct Answer
    A. Requires more driving power, for a given RF power output, than a grounded-cathode RF power amplifier.
    Explanation
    A grounded-grid RF power amplifier requires more driving power, for a given RF power output, than a grounded-cathode RF power amplifier. This is because in a grounded-grid configuration, the input signal is applied to the grid, which is at RF ground potential. This means that the grid is at a lower voltage than the cathode, which requires a higher input signal to overcome the bias voltage and drive the amplifier to produce the desired RF power output. In contrast, a grounded-cathode amplifier has the input signal applied to the cathode, which is at a higher voltage, requiring less driving power to achieve the same RF power output.

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  • 18. 

    An advantage of a grounded-grid RF power amplifier over a grounded-cathode RF poweramplifier is the fact that the grounded-grid circuit

    • Has excellent sensitivity.

    • Exhibits high input impedance.

    • Produces little or no noise in the input.

    • Is more stable.

    Correct Answer
    A. Is more stable.
    Explanation
    The grounded-grid RF power amplifier is more stable compared to the grounded-cathode RF power amplifier. This is because the grounded-grid circuit provides better control over the gain and stability of the amplifier. It has a lower output impedance, which helps in reducing the risk of instability and oscillation. Additionally, the grounded-grid configuration allows for better feedback control, which further enhances stability. Overall, the stability of the grounded-grid RF power amplifier makes it a preferred choice in certain applications where reliability and consistent performance are crucial.

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  • 19. 

    A screen grid enhances tube operation by

    • Increasing the gain, helping the circuit to oscillate more easily.

    • Decreasing the plate voltage required to produce oscillation.

    • Minimizing the risk that a tube amplifier will break into oscillation.

    • Pulling excess electrons from the plate.

    Correct Answer
    A. Minimizing the risk that a tube amplifier will break into oscillation.
    Explanation
    A screen grid enhances tube operation by minimizing the risk that a tube amplifier will break into oscillation. The screen grid acts as a shield between the control grid and the plate, preventing unwanted feedback and oscillation. It helps to stabilize the amplifier and ensure that it operates within its intended frequency range without any instability or self-oscillation. By minimizing the risk of oscillation, the screen grid allows the tube amplifier to function properly and produce a clean and stable output signal.

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  • 20. 

    A heptode tube has

    • One plate.

    • Two plates.

    • Three plates.

    • Four plates.

    Correct Answer
    A. One plate.
    Explanation
    A heptode tube has one plate because the term "heptode" refers to a type of vacuum tube that contains seven elements or electrodes. These elements typically include a cathode, control grid, screen grid, suppressor grid, and three plates. However, in the case of a heptode tube, there is only one plate.

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  • Current Version
  • Jul 22, 2024
    Quiz Edited by
    ProProfs Editorial Team
  • Dec 07, 2010
    Quiz Created by
    BATANGMAGALING
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