**76. The apparent power drawn by an A.C. circuit is 10 kVA and active power is 8 kW. The reactive power in the circuit is**

(a) 4 kVAR

(b) 6 kVAR

(c) 8 kVAR

(d) 16 kVAR

**Ans: b**

**77. What will be the phase angle between two alternating waves of equal frequency, when one wave attains maximum value the other is at zero value ?**

(a) 0°

(b) 45°

(c) 90°

(d) 180°

**Ans: c**

**78. The purpose of a parallel circuit resonance is to magnify**

(a) current

(b) voltage

(c) power

(d) frequency

**Ans: b**

**79. In an A.C. circuit power is dissipated in**

(a) resistance only

(b) inductance only

(c) capacitance only

(d) none of the above

**Ans: a**

**80. In a parallel R-C circuit, the current always______the applied voltage**

(a) lags

(b) leads

(c) remains in phase with

(d) none of the above

**Ans: b**

**81. At very low frequencies a series R-C circuit behaves as almost purely**

(a) resistive

(b) inductive

(c) capacitive

(d) none of the above

**Ans: c**

**82. Skin effect occurs when a conductor carries current at _____ frequencies.**

(a) very low

(b) low

(c) medium

(d) high

**Ans: d**

**83. At ______ frequencies the parallel R-L circuit behaves as purely resistive.**

(a) low

(b) very low

(c) high

(d) very high

**Ans: d**

**84. In a sine wave the slope is constant**

(a) between 0° and 90°

(b) between 90° and 180°

(c) between 180° and 270°

(d) no where

**Ans: d**

**85. The power is measured in terms of decibles in case of**

(a) electronic equipment

(b) transformers

(c) current transformers

(d) auto transformers

**Ans: a**

**86. Capacitive susceptance is a measure of**

(a) reactive power in a circuit

(b) the extent of neutralisation of reactive power in a circuit

(c) a purely capacitive circuit’s ability to pass current

(d) a purely capacitive circuit’s ability to resist the flow of current

**Ans: c**

**87. Which of the following statements pertains to resistors only ?**

(a) can dissipate considerable amount of power

(6) can act as energy storage devices

(c) connecting them in parallel in¬creases the total value

(d) oppose sudden changes in voltage

**Ans: a**

**88. Which of the following refers to a parallel circuit ?**

(a) The current through each element is same

(b) The voltage across element is in proportion to it’s resistance value

(c) The equivalent resistance is greater than any one of the resistors

(d) The current through any one element is less than the source current

**Ans: d**

**89. A phasor is**

(a) a line which represents the mag¬nitude and phase of an alternating quantity

(b) a line representing the magnitude and direction of an alternating quantity

(c) a coloured tag or band for distinction between different phases of a 3-phase supply

(d) an instrument used for measuring phases of an unbalanced 3-phase load

**Ans: a**

**89. A parallel AC. circuit in resonance will**

(a) have a high voltage developed across each inductive and capacitive section

(b) have a high impedance

(c) act like a resistor of low value

(d) have current in each section equal to the line current

**Ans: b**

**90. Wire-wound resistors are unsuitable for use at high frequencies because they**

(a) create more electrical noise

(b) are likely to melt under excessive eddy current heat

(c) consume more power

(d) exhibit unwanted inductive and capacitive effects

**Ans**: d

**91. The inductance of a coil can be increased by**

(a) increasing core length

(b) decreasing the number of turns

(c) decreasing the diameter of the former

(d) choosing core material having high relative permeability

**Ans: d**

**92. In a three-phase supply floating neutral is undesirable because it way give rise to**

(a) high voltage across the load

(b) low voltage across the load

(c) unequal line voltages across the load

**Ans: c**

**93. Which of the following waves has the highest value of peak factor ?**

(a) Square wave

(b) Sine wave

(c) Half wave rectified sine wave

(d) Triangular wave

**Ans: c**

**94. The frequency of domestic power supply in India is**

(a) 200 Hz

(b) 100 Hz

(c) 60 Hz

(d) 50 Hz

**Ans: d**

**95. The r.m.s. value of half wave rectified sine wave is 200 V. The r.m.s. value of full wave rectified AC. will be**

(a) 282.8 V

(b) 141.4 V

(c) 111 V

(d) 100 V

**Ans: a**

**96. The r.m.s. value of pure cosine function is**

(a) 0.5 of peak value

(b) 0.707 of peak value

(c) same as peak value

(d) zero

**Ans: b**

**97. Ohm is unit of all of the following except**

(a) inductive reactance

(b) capacitive reactance

(c) resistance

(d) capacitance

**Ans: d**

**98. The series and parallel resonance on L-C circui’ differs in that**

(a) series resistance needs a low-resistance ource for sharp rise in current

(b) series resonance needs a high-resistance source for sharp increase in current

(c) parallel resonance needs a low-resistance source for a sharp in¬crease in impedance

(d) parallel resonance needs a low-resistance source for a sharp rise in line current

**Ans: a**

**99. The phasors for which of the following pair are 180° out of phase for VL, VC and VR?**

(a) Vc and VR

(b) VL and VR

(c) Vc and VL

(d) none of the above

**Ans: c**

**100. The frequency of an alternating current is**

(a) the speed with which the alternator runs

(b) the number of cycles generated in one minute

(c) the number of waves passing through a point in one second

(d) the number of electrons passing through a point in one second

**Ans: c**

**101. A pure capacitor connected across an A.C. voltage consumed 50 W. This is due to**

(a) the capacitive reactance in ohms

(b) the current flowing in capacitor

(c) the size of the capacitor being quite big

(d) the statement is incorrect

**Ans: d**

**102. The power factor of a D.C. circuit is always**

(a) less than unity

(b) unity

(c) greater than unity

(d) zero

**Ans: b**

**103. The product of apparent power and cosine of the phase angle between circuit voltage and current is**

(a) true power

(b) reactive power

(c) volt-amperes

(d) instantaneous power

**Ans: a**

**104. The equation of 50 Hz current sine wave having r.m.s. value of 60 A is**

(a) 60 sin 25 t

(b) 60 sin 50 t

(c) 84.84 sin 3141

(d) 42.42 sin 314 t

**Ans: c**

**105. An A.C. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms,**

(a) the current through the resistance is more

(b) the current through the resistance is less

(c) both resistance and inductance carry equal currents

(d) none of the above

**Ans: c**

**106. In a pure inductive circuit if the supply frequency is reduced to 1/2, the current will**

(a) be reduced by half

(b) be doubled

(c) be four times as high

(d) be reduced to one fourth

**Ans: b**

**107. In a pure capacitive circuit if the supply frequency is reduced to 1/2, the current will**

(a) be reduced by half

(b) be doubled

(c) be four times at high

(d) be reduced to one fourth

**Ans: a**

**108. When an alternating current passes through an ohmic resistance the electrical power converted into heat is**

(a) apparent power

(b) true power

(c) reactive power

(d) none of the above

**Ans: b**

**109. In each of the three coils of a three phase generator, an alternating voltage having an r.m.s. value of 220 V is induced. Which of the following values is indicated by the voltmeters ?**

(a) 220 V

(b) 220V3V

(c) 220/V3 V

(d) none of the above

**Ans: a**