267. The primary current in a current transformer is dictated by
A. the secondary burden
B. the core of the transformer
C. the load current
D. none of the above

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268. A sinusoidal source of voltage V and frequency f is connected to a series circuit of variable resistance, R and a fixed reactance,X. The locus of the tip of the current-phasor, I, as R is yarded from 0 to 00 is
A. a semicircle with a diameter of V/X.
B. a straight line with a slope of R/X.
C. an ellipse with V/R as major axis.
D. a circle of radius R/X and origin at(0, V/2).

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269. A d.c. voltmeter has a sensitivity of 1000 0./volt. When it measures half full scale in 100V range, the current through the voltmeter is
A. 1 00 mA
B. 1 mA
C. 0.5 rnA
D. 50 mA

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270. A moving coil galvanometer is made into a d.c. ammeter by connecting
A. a low resistance across the meter
B. a high resistance in series with the meter
C. a pure inductance across the meter
D. a capacitor in series with the meter

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271. Electrodynamic type wattmeters have large errors while measuring power in ac circuit at low power factor conditions, since the voltage across and the current through the
A. current coil are not in phase.
B. current coil are not in quadrature.
C. pressure coil are not in phase.
D. pressure coil are not in quadrature.

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272. The two wattmeter method is used to measure active power on a three phase, three wire system. If the phase voltage is unbalanced, then the power reading is
A. affected by both negative sequence and zero sequence voltages
B. affected by negative sequence voltages but not by zero sequence voltages
C. affected by zero sequence voltages butnot by negative sequence voltages
D. not affected by negative or zero sequence voltages.

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273. The minimum number of wattmeter (s) required to measure 3-phase, 3-wire balanced or unbalanced power is
A.1
B.2
C.3
D.4

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