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  • Question

  • A dc chopper V = 500 V feeds an electric fraction dc series motor. The chopping frequency is 400 Hz. The series inductance required to limit the maximum current swing to 10 A is


  • Options
  • A. 20 mH
  • B. about 31 mH
  • C. about 51 mH
  • D. about 92 mH

  • Correct Answer
  • about 31 mH 

    Explanation
    A dc chopper V = 500 V feeds an electric fraction dc series motor. The chopping frequency is 400 Hz..

    More questions

    • 1. As compared to dimensions of most feeds, the skin depth at microwave frequencies is

    • Options
    • A. of the same magnitude
    • B. much larger
    • C. much smaller
    • D. either (b) or (c)
      • Discuss
    • 2. For a 1 cm x 2 cm air filled rectangular waveguide the maximum frequency should be less than about

    • Options
    • A. 1000 MHz
    • B. 5000 MHz
    • C. 14000 MHz
    • D. 140000 MHz
      • Discuss
    • 3. In a radio receiver

    • Options
    • A. all stages contribute equally to noise
    • B. RF stage has no effect on S/N ratio
    • C. mixer stage contributes most of the noise generated
      • Discuss
    • 4. As compared to an ordinary semiconductor diode, a Schottky diode

    • Options
    • A. has higher reverse saturation current
    • B. has higher reverse saturation current and higher cut in voltage
    • C. has higher reverse saturation current and lower cut in voltage
    • D. has lower reverse saturation current and lower cut in voltage
      • Discuss
    • 5. A 3 port circulator is in the given figure. Its scattering matrix is

    • Options
    • A.
    • B.
    • C.
    • D.
      • Discuss
    • 6. The total field developed by an antenna array at a distant point is

    • Options
    • A. phasor sum of fields produced by individual antennas of the array
    • B. algebraic sum of fields produced by individual antennas of the array
    • C. either (a) or (b) depending on type of array
    • D. neither (a) nor (b)
      • Discuss
    • 7. A standard cell of 1.0185 V is used with a slide wire potentiometer. The balance was obtained at 60 cm. When an unknown emf was connected, the balance was obtained at 82 cm. The magnitude of unknown emf is

    • Options
    • A. 1.39 V
    • B. 0.75 V
    • C. 13.9 V
    • D. 7.45 V
      • Discuss
    • 8. The number of valence electrons in donor impurity are

    • Options
    • A. 5
    • B. 4
    • C. 3
    • D. 1
      • Discuss
    • 9. Assertion (A): A DIAC has four layers but only two terminals.

      Reason (R): A DIAC can conduct in both directions.


    • 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
    • 10. A NAND gate has 3 inputs and one output. The number of thyristors required for this gate are

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

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