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 𝑒 = 200 𝑠𝑖𝑛 314𝑡 is applied to a device which offers an ohmic
    resistance of 200Ω 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 𝑰𝒐 = √𝟐 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, 𝑦 =
    𝑦𝑚𝑎𝑥 𝑠𝑖𝑛𝜔𝑡?𝝅𝟒
    .
  • What is the angle in NE quadrant corresponding to the average value of the quantity,
    𝑦 = 𝑦𝑚𝑎𝑥𝑠𝑖𝑛𝜔𝑡? 0.69 rad.

  • Two currents represented by 𝑖1 = 50 sin 𝜔𝑡 , 𝑖12 = 100 sin(𝜔𝑡 + 45 °) 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 𝑰𝒓𝒎𝒔 = 𝟏𝟎𝑨.

  • The rms value of the voltage shown in Fig. 7 is𝒚𝒎𝒂𝒙√𝟑
    .
  • The peak factor for the above voltage is 1.41. ??

  • The average value for above voltage is𝒚𝒎𝒂𝒙𝟐
    .
  • The form factor for the above voltage is𝟐√𝟑
    .
  • With reference to Fig.8 which statement is correct? Current 𝒊𝟐 is leading current 𝒊𝟏.

Questions 57 to 60 refer to the following data:
An alternating quantity increases uniformly from 0 to 0° at 𝐹𝑚 at 𝛼; remains constant
from 𝛼 to (𝜋 − 𝛼) and decreases uniformly from 𝐹𝑚 at (𝜋 − 𝛼) to 0 at 𝜋.

  • The rms value of the wave for one half cycle wil be𝑭𝒎(𝝅−𝜶)𝝅
    .
  • The average value of the wave for one half cycle will be𝟐𝑭𝒎𝝅
    .
  • In above case when 𝛼 =𝜋9, the rms value will be𝟑𝑭𝒎𝟓
    .
  • In the above case when 𝛼 =𝜋2, the rms will be𝑭𝒎𝟐
    .