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Home ‣ Electronics and Communication Engineering ‣ Microwave Communication See What Others Are Saying!
  • Question

  • Assertion (A): In the interaction region of magnetron an electron is subjected to three forces: force due to electric field, force due to magnetic field and centrifugal force.

    Reason (R): The mechanism of generation of microwaves, in a magnetron, involves interaction of electromagnetic fields with electrons moving in static electric and magnetic fields oriented at right angles to each other.


  • 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 

    Explanation
    It is somewhat similar to TWT and can deliver microwave power over a wide frequency band.

    It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT.

    The growing RF wave travels in opposite direction to the electron beam.

    The frequency of wave can be changed by changing the voltage which controls the beam velocity.

    Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current.

    It features are:

    1. Frequency range - 1 GHz to 1000 GHz.

    2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed).

    It is used as signal source in transmitters and instruments.

    More questions

    • 1. A radar has a maximum range of 120 km. The maximum allowable pulse repetition frequency for unambiguous reception is

    • Options
    • A. 1250
    • B. 330
    • C. 2500
    • D. 8330
      • Discuss
    • 2. An unmodulated voltage 10 V effective is applied to a dioxide detector in which load resistance is 4 x 10-5 ohms. A micrometer shows that the rectified DC current in this resistance is 30 A. The input resistance of the detector is

    • Options
    • A. 114 kW
    • B. 336 kW
    • C. 384 kW
    • D. 455 kW
      • Discuss
    • 3. For a BJT a = 0.98, then ? =

    • Options
    • A. 0.02
    • B. 0.5
    • C. 4.9
    • D. 48
      • Discuss
    • 4. If the temperature of an extrinsic semiconductor is increased so that the intrinsic carrier concentration is doubled, then

    • Options
    • A. the majority carrier density is doubled
    • B. the minority carrier density is doubled
    • C. the minority carrier density becomes 4 times the original value
    • D. both the majority and minority carrier densities double
      • Discuss
    • 5. A cycloconverter is

    • Options
    • A. ac-dc converter
    • B. dc-ac converter
    • C. dc-dc converter
    • D. ac-ac converter
      • Discuss
    • 6. Consider the following DO statement in Fortran 77

      DO 52 N = 1, 10, 3

      The number of DO loop executions in the above statement is

    • Options
    • A. 1
    • B. 10
    • C. 3
    • D. 4
      • Discuss
    • 7. In a single phase semiconverter feeding a highly inductive load, the load current is

    • Options
    • A. sinusoidal
    • B. nearly constant
    • C. absolutely constant
    • D. rectangular
      • Discuss
    • 8. If ton and toff are the turn on and turn off times of a thyristor, then

    • Options
    • A. ton and toff are almost equal
    • B. ton >> toff
    • C. toff >> ton
    • D. ton is about twice toff
      • Discuss
    • 9. Which inverter circuit uses coupled inductors?

    • Options
    • A. Modified McMurray full bridge inverter
    • B. McMurray Bedford half bridge inverter
    • C. Modified McMurray Bedford half bridge inverter
    • D. Both (b) and (c)
      • Discuss
    • 10. If there are no permanent dipoles in a dielectric material, the dielectric constant is independent of temperature.

    • Options
    • A. True
    • B. False
      • Discuss

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