Vacuum Tubes

81. What started the conduction in a cold cathode tube?

1. Thermionic emission
2. Natural sources
3. Secondary emission
4. Thermal sources

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82. What transformer secondary voltage is utilized in a center-tap circuit?

1. One-half
2. One-third
3. full
4. One-eighth

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83. What would cause the plate current to increase in a pentode tube?

1. A short circuit between the plate and the screen grid
2. An open circuit in the lead that is connected to the
3. A short circuit between the suppressor grid and the cathode
4. A short circuit between the control grid and the cathode

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84. When a thyratron tube has fired one thing that will cause it to stop conducting is

1. a more positive on the plate
2. a more negative voltage on the control electrode
3. a more positive voltage on the control electrode
4. a negative voltage on the plate

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85. When the control grid of a triode is operated with positive potential with respect to cathode

1. the grid resistance decreases
2. the grid may overheat
3. the plate current decreases sharply
4. the grid resistance increases

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86. When the gas pressure in a gas-filled diode is increased, its PlV rating

1. remains unchanged
2. decreases
3. increases
4. becomes infinite

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87. When the temperature of an emitter is increased two times, the electron emission

1. increases two times
2. increases four times
3. increases several million times
4. decreases two times

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88. Which can be used for proper high frequency amplification?

1. Triode
2. Tetrode
3. Pentode
4. Diode

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89. Which emission is most widely used in practice?

1. Field
2. Secondary
3. Thermionic
4. Photo

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90. Which emitter is most commonly used in the tubes of a radio receiver?

1. Tungsten
2. Oxide coated
3. Thoriated tungsten
4. Constantan

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