1.
A major difference between a triode tube and an N-channel FET is the fact that
Correct Answer
C. 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.
2.
The control grid of a vacuum tube is the electrical counterpart of the
Correct Answer
D. Gate of an FET.
Explanation
The control grid of a vacuum tube is the electrical counterpart of the gate of a Field-Effect Transistor (FET). Both the control grid and the gate are used to control the flow of current in their respective devices. In a vacuum tube, the control grid is a wire mesh or a metal cylinder that surrounds the cathode and is used to modulate the flow of electrons. Similarly, in an FET, the gate is a terminal that controls the flow of current through a semiconductor channel by applying a voltage. Therefore, the control grid of a vacuum tube is equivalent to the gate of an FET.
3.
In a tetrode tube, the charge carriers are
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.
4.
Which factor is most significant in limiting the maximum frequency at which a tube canoperate?
Correct Answer
B. 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.
5.
In a tube with a directly heated cathode,
Correct Answer
C. 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.
6.
In a tube with a cold cathode,
Correct Answer
D. 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.
7.
A screen grid enhances tube operation by
Correct Answer
C. 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.
8.
A tube with three grids is called a
Correct Answer
C. 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.
9.
A tube with four grids is called a
Correct Answer
D. Hexode.
10.
An advantage of a grounded-grid RF power amplifier over a grounded-cathode RF poweramplifier is the fact that the grounded-grid circuit
Correct Answer
D. 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.
11.
A heptode tube has
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.
12.
The electron gun in a CRT is another name for its
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.
13.
The electron beam in an electrostatic CRT is bent by
Correct Answer
B. 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.
14.
A grounded-grid 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.
15.
In a Klystron, the electron-beam density varies as a result of
Correct Answer
C. 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.
16.
A vidicon camera tube is noted for its
Correct Answer
C. 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.
17.
The plate in a tetrode tube is normally connected to
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.
18.
The screen grid in a tetrode tube is normally connected to
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.
19.
Which of the following is most suitable for measuring the intensity of dim light?
Correct Answer
B. 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.
20.
In a dissector tube, the aperture size is directly related to the
Correct Answer
D. 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.