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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. Tesla is a unit of

    • Options
    • A. flux
    • B. field strength
    • C. flux density
    • D. MMF
      • Discuss
    • 2. In a receiver, which of the following device has IF input but RF output?

    • Options
    • A. Demodulator
    • B. Loudspeaker
    • C. Audio amplifier
    • D. Frequency changer
      • Discuss
    • 3. In Fermi-Dirac statistics, the probability of electron occupation of an energy level equal to Fermi level is

    • Options
    • A. 0
    • B. 0.25
    • C. 0.5
    • D. 1
      • Discuss
    • 4. In a shield helix

    • Options
    • A. the spacing between adjacent turns is very large
    • B. the spacing between adjacent turns approaches zero
    • C. the spacing between adjacent turns approaches zero and wire thickness approaches zero
    • D. the spacing between adjacent turns is very large wire thickness approaches zero
      • Discuss
    • 5. Match the following:

      List I List II
      A. 200 MHz 1. SHF
      B. 20 GHz 2. UHF
      C. 500 kHz 3. VHF
      D. 500 MHz 4. MF


    • Options
    • A. A-3, B-1, C-4, D-2
    • B. A-3, B-2, C-4, D-1
    • C. A-3, B-4, C-1, D-2
    • D. A-3, B-4, C-2, D-1
      • Discuss
    • 6. A line of characteristic impedance Z0 branches into two line each with characteristic impedance Z0. The refracted voltage is

    • Options
    • A. zero
    • B. infinite
    • C. equal to incident voltage
    • D. two third of incident voltage
      • Discuss
    • 7. Iron has a body centred cubic structure.

    • Options
    • A. True
    • B. False
      • Discuss
    • 8. A surge voltage

    • Options
    • A. has very high magnitude and very long duration
    • B. has very high magnitude and very small duration
    • C. has very high magnitude and very small duration and can be positive or negative
    • D. can be only positive
      • Discuss
    • 9. The Ohm's law for conduction in metals is

    • Options
    • A. J = ?E
    • B. J =
    • C. J ? ?E
    • D. J ?
      • Discuss
    • 10. The following components are used to measure power output of a 2 kW TWT amplifier

      1. TWT
      2. Low pass/High pass filter
      3. Low power 20 dB attenuator
      4. 40 dB directional coupler with matched load
      5. Power meter.
      The correct sequence of connections of these components is:

    • Options
    • A. 1, 4, 2, 3, 5
    • B. 1, 3, 4, 2, 5
    • C. 1, 2, 4, 3, 5
    • D. 1, 4, 3, 2, 5
      • Discuss

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