AC Fundamentals Objectives Part 03

  • Two waves, a sine wave and a half wave rectified ac, are shown in figure 6
    The value of which of the following parameters for half wave rectified ac will be more?
    Form factor.
  • In the above case the value of which parameter for full sine wave will be more?
    Average value.
  • An alternating voltage ๐‘’ = 200 ๐‘ ๐‘–๐‘› 314๐‘ก is applied to a device which offers an ohmic
    resistance of 200ฮฉ to the flow of current in one direction while entirely preventing the
    flow in the opposite direction. The value of current will be 5 A. ??

  • In the above case, the average value of the current will be 3.18 A.

  • When the sole purpose of the alternating current is to produce heat, the selection of
    conductor is based on rms value of current.
  • The r.m.s value of a.c. is related to peak value of a.c. by the equation ๐‘ฐ๐’ = โˆš๐Ÿ I r.m.s.

  • The form factor of dc supply voltage is always Unity.

  • What is the angle in the NE quadrant corresponding to a rms value of the quantity, ๐‘ฆ =
    ๐‘ฆ๐‘š๐‘Ž๐‘ฅ ๐‘ ๐‘–๐‘›๐œ”๐‘ก?๐…๐Ÿ’
    .
  • What is the angle in NE quadrant corresponding to the average value of the quantity,
    ๐‘ฆ = ๐‘ฆ๐‘š๐‘Ž๐‘ฅ๐‘ ๐‘–๐‘›๐œ”๐‘ก? 0.69 rad.

  • Two currents represented by ๐‘–1 = 50 sin ๐œ”๐‘ก , ๐‘–12 = 100 sin(๐œ”๐‘ก + 45 ยฐ) are fed into
    a common conductor. The rms value of the current will be between 50 A and 100 A.

Questions 51 to 54 refer to the fig7.

  • A 1000 W heater is rated to operate at a direct current of 10A. If the heater is supplied
    alternating current, for producing the same quantity of heat, the value of current should
    be ๐‘ฐ๐’“๐’Ž๐’” = ๐Ÿ๐ŸŽ๐‘จ.

  • The rms value of the voltage shown in Fig. 7 is๐’š๐’Ž๐’‚๐’™โˆš๐Ÿ‘
    .
  • The peak factor for the above voltage is 1.41. ??

  • The average value for above voltage is๐’š๐’Ž๐’‚๐’™๐Ÿ
    .
  • The form factor for the above voltage is๐Ÿโˆš๐Ÿ‘
    .
  • With reference to Fig.8 which statement is correct? Current ๐’Š๐Ÿ is leading current ๐’Š๐Ÿ.

Questions 57 to 60 refer to the following data:
An alternating quantity increases uniformly from 0 to 0ยฐ at ๐น๐‘š at ๐›ผ; remains constant
from ๐›ผ to (๐œ‹ โˆ’ ๐›ผ) and decreases uniformly from ๐น๐‘š at (๐œ‹ โˆ’ ๐›ผ) to 0 at ๐œ‹.

  • The rms value of the wave for one half cycle wil be๐‘ญ๐’Ž(๐…โˆ’๐œถ)๐…
    .
  • The average value of the wave for one half cycle will be๐Ÿ๐‘ญ๐’Ž๐…
    .
  • In above case when ๐›ผ =๐œ‹9, the rms value will be๐Ÿ‘๐‘ญ๐’Ž๐Ÿ“
    .
  • In the above case when ๐›ผ =๐œ‹2, the rms will be๐‘ญ๐’Ž๐Ÿ
    .