Measurement and Instrumentation

91. To avoid the effect of stray magnetic field in A.C. bridges we can use

1. magnetic screening
2. Wagner earthing device
3. wave filters
4. any of the above

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92. To measure a resistance with the help of a potentiometer it is

1. necessary to standardise the potentiometer
2. not necessary to standardise the potentiometer
3. necessary to use a volt ratio box in conjunction with the potentiometer
4. none of the above

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93. To measure an A. C. voltage by using an A.C. potentiometer, it is desirable that the supply for the potentiometer in taken

1. from a source which is not the same as the unknown voltage
2. from a battery
3. from the same source as the unknown voltage
4. any of the above

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94. To measure radio frequency, the suitable frequency meter is

1. Weston frequency meter
2. reed vibrator frequency meter
3. heterodoxy frequency meter
4. electrical resonance frequency meter

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95. Two holes in the disc of energy meter are drilled at the opposite sides of the spindle to

1. improve its ventilation
2. eliminate creeping at no load
3. increase its deflecting torque
4. increase its braking torque

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96. Various adjustments in an energy meter include

1. light load or friction
2. lag and creep
3. overload and voltage compensation
4. temperature compensation
5. all of the above

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97. Volt box is a component to

1. extend voltage range
2. measure voltage
3. compare voltage in a box
4. none of the above

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98. Wagner earthing device is used to eliminate errors due to

1. electrostatic coupling
2. electromagnetic coupling
3. both (a) and (b)
4. none of the above

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99. Wattmeter cannot be designed on the principle of

1. electrostatic instrument
2. thermocouple instrument
3. moving iron instrument
4. electrodynamic instrument

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100. When a capacitor was connected to the terminal of ohmmeter, the pointer indicated a low resistance initially and then slowly came to infinity position. This shows that capacitor is

1. short-circuited
2. all right
3. faulty
4. none of the above

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