Measurements and Instrumentation
Kelvin's double bridge is used to measure low resistances because
Answer: D
Effect of lead and contact resistances is very important in measurement of low resistances.
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Two resistors R1 = 36 Ω ± 5% and R2 = 75 Ω ± 5% are connected in series. The total resistance is
Answer: C
Total maximum error ± (1.8 + 3.75) = ± 5.55 Ω.
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A single phase energy meter has the rating 1200 resolutions/ kWh. If a 500 W electric gadget is used for 4 hours, the energy meter will make
Answer: D
0.5 x 4 = 2 kWh = 2 x 1200 revolutions.
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The scale of hot wire instrument is linear.
Answer: B
Since reading is proportional to I2, the scale is non-linear.
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A moving iron voltmeter reads 250 V when connected to 250 V dc. If connected to 250 V 50 Hz, the voltmeter reading is likely to be
Answer: C
The inductance of coil will allow slightly less ac current. Hence reading slightly less.
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The resistance of a 125 Ω strain gauge changes by 1 ohm for 4000 micro strain. The gauge factor is
Answer: B
.
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A dynamometer wattmeter is connected in ac circuit. The measured power is
Answer: B
All wattmeters measure average power over a cycle.
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Which of the following instruments has non-linear scale?
1.Moving coil instrument
2.Moving iron instrument
3.Electrostatic instrument
4.Rectifier instrument
Select the answer as per following codes
Answer: B
Moving coil and Rectifier Instruments have linear scale. Moving iron and electrostatic have non-linear scale.
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Assertion (A): Schering bridge is a low voltage bridge.
Reason (R): Schering bridge is very commonly used for measurement of capacitance.
Answer: D
Schering bridge is a high voltage bridge.
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The resistance of a 125 Ω strain gauge changes by 1 ohm for 4000 micro strain. The gauge factor is
Answer: B
.
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