Vacuum Tubes

11. A vacuum diode can be used as

1. an amplifier
2. an oscillator
3. a rectifier
4. a regulator

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12. A vacuum tube is a _________ device.

1. linear
2. exponential
3. non-linear
4. bilateral

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13. A vacuum tube is normally operated in the temperature saturation region.

1. To protect against filament aging
2. To keep the tube envelope hot
3. To disperse the space charge
4. Keep the tube envelope cold

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14. A vacuum tube will conduct only if its plate is _________ with respect to the cathode.

1. positive
2. negative
3. at zero potential
4. at infinite potential

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15. A voltage amplifier is designed to have

1. high μ and R_L
2. low μ and high R_L
3. high rp and low R_L
4. high μ and low R_L

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16. Before ionisation, a gas- filled tube has a _________ resistance.

1. very high
2. very small
3. small
4. zero

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17. Class C amplifiers are used as _________ amplifiers.

1. audio-frequency voltage
2. radio-frequency
3. audio-frequency power
4. audio-frequency current

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18. Direct coupling is used for _________ amplification.

1. very low frequency
2. radio-frequency
3. audio-frequency
4. ultra high frequency

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19. Directly heated cathode require _________ amount of heating

1. very small
2. large
3. small
4. very large

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20. Field emission is utilized in the mechanism of

1. vacuum tubes
2. gas-filled tubes
3. mercury pool devices
4. TV picture tubes

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