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  • Question

  • A dc series motor is coupled to a load whose torque is proportional to speed. It is fed by a single phase ac supply through a full converter. When speed is 500 rpm, firing angle is 45°. It is desired to raise the speed. It will be necessary to


  • Options
  • A. decrease the firing angle
  • B. increase the firing angle
  • C. either decrease or increase the firing angle depending on the required speed
  • D. decrease the load torque

  • Correct Answer
  • decrease the firing angle 

    • More questions

    • 1. If an amplifier with gain of - 1000 and feedback factor ? = - 0.1 had a gain change of 20% due to temperature, the change in gain of the feedback amplifier would be

    • Options
    • A. 10%
    • B. 5%
    • C. 0.2%
    • D. 0.01%
      • Discuss
    • 2. Permeability is analogous to

    • Options
    • A. resistivity
    • B. retentivity
    • C. conductivity
    • D. coercivity
      • Discuss
    • 3. In a Gunn diode oscillator drift velocity of electron is 107 cm/s and active region length is 10 x 10-4 cm. The natural frequency of oscillation is

    • Options
    • A. 1 MHz
    • B. 10 MHz
    • C. 1 GHz
    • D. 10 GHz
      • Discuss
    • 4. A cycloconverter is a group of controlled rectifiers.

    • Options
    • A. True
    • B. False
      • Discuss
    • 5. If the valence electron is separated from a copper atom, the remaining part of atom has a net charge of

    • Options
    • A. 1
    • B. - 1
    • C. 0
    • D. + 3
      • Discuss
    • 6. A single phase bridge type cycloconverter uses eight thyristors.

    • Options
    • A. True
    • B. False
      • Discuss
    • 7. ?r is determined by the atomic structure of the dielectric.

    • Options
    • A. True
    • B. False
      • Discuss
    • 8. An SBS can conduct is one direction only.

    • Options
    • A. True
    • B. False
      • Discuss
    • 9. The resistivity of intrinsic semiconductors, at room temperature, is of the order of

    • Options
    • A. 1 ?-m
    • B. 1000 ?-m
    • C. 106 ?-m
    • D. 10-3 ?-m
      • Discuss
    • 10. The orientation polarization of a polyatomic gas is inversely proportional to absolute temperature.

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

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