1) Aphasoris________? a. a line which represents the magnitude 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
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2) Which of the following statements pertains to resistors only _____________? a. can dissipate considerable amount of power b. can act as energy storage devices c. connecting them in parallel in¬creases the total value d. oppose sudden changes in voltage
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3) 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
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4) The purpose of a parallel circuit resonance is to magnify________? a. current b. voltage c. power d. frequency
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5) All definitions of power factor of a series R-L-C circuit are correct except__________? a. ratio of net reactance and impedance b. ratio of kW and kVA c. ratio of J and Z d. ratio of W and VA
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6) In AC. circuits, laminated iron is invariably used in order to__________? a. reduce eddy current loss b. increase heat radiation c. make assembly cheap and easier d. reduce circuit permeability
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7) 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
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8) 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
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9) The ratio of active power to apparent power is known as factor__________? a. demand b. load c. power d. form
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10) The effective resistance of an iron-cored choke working on ordinary supply frequency is more than its true resistance because of____________? a. iron loss in core b. skin effect c. increase in temperature d. capacitive effect between adjacent coil turns
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11) A pure inductance connected across 250 V, 50 Hz supply consumes 100 W. This consumption can be attributed to_________? a. the big size of the inductor b. the reactance of the inductor c. the current flowing in the inductor d. the statement given is false
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12) The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA The power drawn by the circuit is__________? a. 12 kW b. 22 kW c. 32 kW d. 64 kW
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13) In an AC. circuit, a low value of kVAR compared with kW indicates_________? a. low efficiency b. high power factor c. unity power factor d. maximum load current
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14) Which of the following coil will have large resonant frequency __________? a. A coil with large resistance b. A coil with low resistance c. A coil with large distributed capacitance d. A coil with low distributed capacitance
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15) If a sinusoidal wave has frequency of 50 Hz with 30 A r.m.s. current which of the following equation represents this wave_________ ? a. 42.42 sin 3141 b. 60 sin 25 t c. 30 sin 50 t d. 84.84 sin 25 t
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16) In a R-L-C circuit_________? a. power is consumed in resistance and is equal to I R b. exchange of power takes place between inductor and supply line c. exchange of power takes place between capacitor and supply line d. exchange of power does not take place between resistance and the supply line e. all above are correct
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17) If resistance is 20 Q. and inductance is 27 in a R-L series circuit, then time constant of this circuit will be________? a. 0.001 s b. 0.1 s c. 10 s d. 100 s
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18) The safest value of current the human body can carry for more than 3 second is_________? a. 4 mA b. 9 mA c. 15 mA d. 25 mA
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19) Time constant of a circuit is the time in seconds taken after the application of voltage to each___________? a. 25% of maximum value b. 50% of maximum value c. 63% of maximum value d. 90% of the maximum value
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20) Power factor of electric bulb is__________? a. zero b. lagging c. leading d. unity
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