Vacuum Tubes

51. The output stage of a practical amplifier always employs what coupling?

1. RC coupling
2. Transformer coupling
3. Direct coupling
4. lmpedance coupling

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52. The peak inverse voltage of a diode is defined as the maximum allowable

1. negative voltage across the load resistor
2. negative voltage applied to plate with respect to cathode
3. positive voltage to plate with respect to cathode
4. positive voltage applied across the load resistor

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53. The plate resistance of a tube is mainly due to

1. space charge
2. electrodes of the tube
3. vacuum in the tube
4. gas in the tube

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54. The PlV of hot cathode gas diode is _________ the equivalent vacuum diode.

1. the same as that of
2. less than
3. more than
4. independent that of

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55. The screen grid is used to

1. increase the capacitance between the second grid and the plate
2. decrease the capacitance between the control grid and the plate
3. reduce the secondary emission effect
4. lower the tube's plate resistance

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56. The screen grid potential is kept _________ plate potential

1. somewhat lower than
2. same as
3. somewhere higher than
4. at zero potential with respect to

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57. The transconductance of a pentode is _________ a triode.

1. more than that of
2. about the same as for
3. less than that of
4. not comparable to that of

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58. The typical application of a cold cathode tube is as a

1. diode
2. tetrode
3. triode
4. pentode

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59. The unit of work function of metals.

1. Joules
2. Watt-hour
3. Electron-volt
4. Watt

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60. The voltage on the suppressor grid of a pentode is generally

1. positive with respect to cathode
2. positive with respect to cathode
3. zero with respect to cathode
4. at zero potential

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