AC Fundamentals MCQs Part 06

101. The instantaneous value of current 𝑖𝐴 at 𝑡=0.35 𝑟𝑚𝑠 will be 20.5 mA.

102. The instantaneous value of current 𝑖𝐵 at 𝑡=0.35 𝑟𝑚𝑠 will be –20.6 mA.

103. What value of dc voltage will produce the same average power as 150V peak sine wave? 106 V.

104. What current will an ammeter show when connected in series with a 32 ohm load that is dissipating a peak power of 288 W? 2.12 A.

105. A 160 W soldering iron is operated from the 60 Hz power line. The resistance of the soldering iron is 75.6 ohms.

106. A certain sine wave is expressed as 𝑒=sin (4000𝑡). The frequency of this sine wave will be 637 Hz.

107. A certain 1-Khz sine wave reaches -70 V at 𝑡=0.6 𝑚𝑠, The peak value of this sine wave will be 118 V.

1. A sine wave of voltage produces a peak current of 12 mA in a 3 KΩ resistor. The average power dissipated in the resistor will be 216 W.

109 In a.c. circuits, the a.c. meters measures r.m.s values.

110 Radio frequency choke is air cored to keep inductive reactance low.

110 Hot wire ammeters are used for measuring only a.c.

112 When 𝑣1=50sin𝜃,𝑣2=30sin(𝜃+25°) and v2=25sin(𝜃−90°),the resultant of (𝑣1 +𝑣2−𝑣3) is given by 𝟖𝟔𝐬𝐢𝐧(𝜽+𝟐𝟔°).

1. 12<30° in rectangular coordinates can be represented as 𝟏𝟎.𝟒+𝒋𝟔.

114 270/1.7 π can be represented in rectangular coordinates as 𝟏𝟓𝟗−𝒋 𝟐𝟏𝟖.

115 A choke coil is used for controlling current in an a.c.circuit only.

116 Ohm’s law (𝐸=𝐼𝑅) can be applied to a.c. but after replacing R by Z (impedance).

117 What frequency is one octave above 110 Hz? 220 Hz.

118 What frequency is the fourth harmonic of 4 Mhz? 16 Mhz.

Questions 119 to 122 refer to data given below:
A 60 Hz power-line voltage of 120 V is applied across a resistance of 10 ohms.

1. The rms current in the circuit is 12 A.

220 The frequency of the current will be 60 Hz.