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  • Question

  • An electric heater is controlled by thyristors through on-off control. If a = 0.4, the heating is


  • Options
  • A. 16% maximum
  • B. 40% of maximum
  • C. 60% of maximum
  • D. 84% of maximum

  • Correct Answer
  • 40% of maximum 

    Explanation
    Vl = V a. Therefore Vl2 - V2 (a). Heating is proportional to a.

    More questions

    • 1. The output frequency of a cycloconverter can be changed by changing the firing angle.

    • Options
    • A. True
    • B. False
      • Discuss
    • 2. Most of the memory chips in static RAM

    • Options
    • A. do not require any supply
    • B. need 2 V supply
    • C. need 5 V supply
    • D. need 12 V supply
      • Discuss
    • 3. In crystalline solids, atoms are stacked in a regular manner.

    • Options
    • A. True
    • B. False
      • Discuss
    • 4. The classes of solid dielectrics are

    • Options
    • A. A, B, C, D, E, F, H
    • B. A E B F H C D
    • C. Y A E B F H C
    • D. A E B F H C
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    • 5. The unit for mmf is

    • Options
    • A. A
    • B. Wb
    • C. T
    • D. V
      • Discuss
    • 6. In a single phase full wave regulator, the firing angles in the positive and negative half cycles are generally

    • Options
    • A. equal
    • B. different
    • C. equal or different
    • D. different but sometimes equal
      • Discuss
    • 7. The real part of complex dielectric constant and tan? for a dielectric are 2.1 and 5 x 10-4 at 100 Hz respectively. The imaginary part of dielectric constant at 100 Hz is

    • Options
    • A. 1.05 x 10-3
    • B. 2.1 x 10-3
    • C. 5 x 10-3
    • D. 1.05 x 10-2
      • Discuss
    • 8. The units for ?r are

    • Options
    • A. Farads
    • B. Farads/m
    • C.
    • D. no units
      • Discuss
    • 9. Tesla is a unit of

    • Options
    • A. flux
    • B. field strength
    • C. flux density
    • D. MMF
      • Discuss
    • 10. 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
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