51. Which of the following devices should be used for accurate measurement of low D.C. voltage ?
(a) Small range moving coil voltmeter
(b) D.C. potentiometer
(c) Small range thermocouple voltmeter
(d) None of the above
Ans: b
52. It is required to measure the true open circuit e.m.f. of a battery. The best device is
(a) D.C. voltmeter
(b) Ammeter and a known resistance
(c) D.C. potentiometer
(d) None of the above
Ans: c
53. A voltage of about 200 V can be measured
(a) directly by a D.C. potentiometer
(b) a D.C. potentiometer in conjunction with a volt ratio box
(c) a D.C. potentiometer in conjunction with a known resistance
(d) none of the above
Ans: b
54. A direct current can be measured by
(a) a D.C. potentiometer directly
(b) a D.C. potentiometer in conjunction with a standard resistance
(c) a D.C. potentiometer in conjunction with a volt ratio box
(d) none of the above
Ans: b
55. To measure a resistance with the help of a potentiometer it is
(a) necessary to standardise the potentiometer
(b) not necessary to standardise the potentiometer
(c) necessary to use a volt ratio box in conjunction with the potentiometer
(d) none of the above
Ans: b
56. A phase shifting transformer is used in conjunction with
(a) D.C. potentiometer
(b) Drysdale potentiometer
(c) A.C. co-ordinate potentiometer
(d) Crompton potentiometer
Ans: b
57. Basically a potentiometer is a device for
(a) comparing two voltages
(b) measuring a current
(c) comparing two currents
(d) measuring a voltage
(e) none of the above
Ans: a
58. In order to achieve high accuracy, the slide wire of a potentiometer should be
(a) as long as possible
(b) as short as possible
(c) neither too small not too large
(d) very thick
Ans: a
59. To measure an A. C. voltage by using an A.C. potentiometer, it is desirable that the supply for the potentiometer in taken
(a) from a source which is not the same as the unknown voltage
(b) from a battery
(c) from the same source as the unknown voltage
(d) any of the above
Ans: c
60. The stator of phase shifting transformer for use in conjunction with an A.C. potentiometer usually has a
(a) single-phase winding
(b) two-phase winding
(c) three-phase winding
(d) any of the above
Ans: b
61. In an AC. co-ordinate potentiometer, the currents in the phase and quadrature potentiometer are adjusted to be
(a) out of phase by 90°
(6) out of phase by 60°
(c) out of phase by 30°
(d) out of phase by 0°
(e) out of phase by 180°
Ans: a
62. A universal RLC bridge uses
(a) Maxwell bridge configuration for measurement of inductance and De Santas bridge for measurement of capacitance
(b) Maxwell Wein bridge for measurement of inductance and modified De Santy’s bridge for measurement of capacitance
(c) Maxwell Wein bridge for measurement of inductance and Wein bridge for measurement of capacitance
(d) Any of the above.
Ans: b
63. For measurements on high voltage capacitors, the suitable bridge is
(a) Wein bridge
(b) Modified De Santy’s bridge
(c) Schering bridge
(d) Any of the above
(e) None of the above
Ans: c
64. In an Anderson bridge, the unknown inductance is measured in terms of
(a) known inductance and resistance
(b) known capacitance and resistance
(c) known resistance
(d) known inductance
Ans: b
65. Wagner earthing device is used to eliminate errors due to
(a) electrostatic coupling
(b) electromagnetic coupling
(c) both (a) and (b)
(d) none of the above
Ans: a
66. For measurement of mutual inductance we can use
(a) Anderson bridge
(b) Maxwell’s bridge
(c) Heaviside bridge
(d) Any of the above
Ans: c
67. For measurement of inductance having high value, we should use
(a) Maxwell’s bridge
(b) Maxwell Wein bridge
(c) Hay’s bridge
(d) Any of the above
Ans: c
68. If the current in a capacitor leads the voltage by 80°, the loss angle of the capacitor is
(a) 10°
(b) 80°
(c) 120°
(d) 170°
Ans: a
69. In a Schering bridge the potential of the detector above earth potential is
(a) a few volts only
(6) 1 kV
(c) 5 kV
(d) 10 kV
Ans: a
70. To avoid the effect of stray magnetic field in A.C. bridges we can use
(a) magnetic screening
(b) Wagner earthing device
(c) wave filters
(d) any of the above
Ans: a
71. If an inductance is connected in one arm of bridge and resistances in the remaining three arms
(a) the bridge can always be balanced
(b) the bridge cannot be balanced
(c) the bridge can be balanced if the resistances have some specific values
Ans: b
72. A power factor meter has
(a) one current circuit and two pres¬sure circuits
(b) one current circuit and one pressure circuit
(c) two current circuits and one pres¬sure circuit
(d) none of the above
Ans: a
73. The two pressure coils of a single phase power factor meter have
(a) the same dimensions and the same number of turns
(b) the same dimension but different number of turns
(c) the same number of turns but different dimensions
(d) none of the above
Ans: a
74. In a single phase power factor meter the phase difference between the currents in the two pressure coils is
(a) exactly 0°
(b) approximately 0°
(c) exactly 90°
(d) approximately 90°
Ans: c
75. In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at
(a) 0°
(b) 60°
(c) 90°
(d) 120°
Ans: d