Discussion
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- Question
Assertion (A): TWT uses a focussing mechanism to prevent the electron beam from spreading.
Reason (R): In a TWT the electron beam has to travel a much longer distance than in klystron.
Options- A. Both A and R are correct and R is correct explanation of A
- B. Both A and R are correct but R is not correct explanation of A
- C. A is correct but R is wrong
- D. A is wrong but R is correct
- Correct Answer
- Both A and R are correct and R is correct explanation of A
ExplanationIn a klystron the resonant structure limits the bandwidth.A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave.
The velocity of wave propagation along the helix structure is less than velocity of light.
The beam and wave travel along the structure at the same speed.
Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave.
Therefore the signal gets strengthened and amplified output is delivered at the other end of tube.
The main features of TWT are :
1. Frequency range - 0.5 GHz to 90 GHz
2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz
3. Efficiency - about 5 to 20%
4. Noise - about 5 dB for low power TWT 25 dB for high power TWT
TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.
More questions
- 1. The maximum signal propagation time of a geosynchronous satellite transmission is about __________ millisecond.
Options- A. 540
- B. 270
- C. 135
- D. 1080 Discuss
Correct Answer: 270
- 2. In carbon resistor colour code, the third band is red. It indicates
Options- A. two zeros
- B. three zeros
- C. multiplier is 0.01
- D. multiplier is 0.1 Discuss
Correct Answer: two zeros
- 3. Low-orbit satellites are not used for communications because they
Options- A. produce sonic booms
- B. do not provide 24 hour/ day contact to the users on Earth
- C. heat up and melt
- D. none Discuss
Correct Answer: heat up and melt
- 4. When a thyristor is conducting, the voltage drop across it is about
Options- A. 1 V
- B. 10 V
- C. 100 V
- D. 0.1 V Discuss
Correct Answer: 1 V
- 5. In a TWT the phase velocity of the axial component of the field on the slow wave structure is kept
Options- A. equal to velocity of electron
- B. slightly less than velocity of electron
- C. slightly more than velocity of electron
- D. equal to velocity of light in free space Discuss
Correct Answer: equal to velocity of electron
- 6. Assertion (A): SUS is a PUT and avalanche diode connected between gate and cathode
Reason (R): SBS has two SUS inbuilt together and connected in anti-parallel
Options- A. Both A and R are correct and R is correct explanation of A
- B. Both A and R correct but R is not correct explanation of A
- C. A is correct but R is wrong
- D. A is wrong but R is correct Discuss
Correct Answer: Both A and R correct but R is not correct explanation of A
- 7. In a CRO which of the following is not a part of electron gun
Options- A. cathode
- B. grid
- C. accelerating anode
- D. X - Y plates Discuss
Correct Answer: X - Y plates
Explanation:
Electron gun consists of cathode, grid and accelerating anode.- 8. Which of the following can be accessed only sequentially?
Options- A. Floppy disk
- B. Hard disk
- C. Magnetic tape
- D. ROM Discuss
Correct Answer: Magnetic tape
Explanation:
Magnetic tape can be accessed only sequentially.- 9. Which of the following is not a valid variable name in C?
Options- A. p o, t
- B. p o t
- C. po_t
- D. p_ot Discuss
Correct Answer: p o, t
Explanation:
Comma is not allowed.- 10. A magnet does not attract
Options- A. nickel
- B. iron
- C. copper
- D. iron and copper Discuss
Correct Answer: copper
Explanation:
Only copper is non-magnetic.
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