Measurements and Instrumentation
Which of the following voltmeters would you use for measuring voltage across 20 kΩ resistance?
Answer: C
Resistance of voltmeter should be very high as compared to 20 kΩ.
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In a resistance strain gauge, G = 2, stress = 1050 kg/cm2, R = 1000 Ω. The value of ΔR will be
Answer: D
.
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It is required to measure angular position. Out of the transducers
1.Circular potentiometer
2.LVDT
3.E pick up
4.Synchro
The proper devices are
Answer: D
LVDT and E pickup are suitable for linear displacement.
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A standard cell of 1.0185 V is used with a slide wire potentiometer. The balance was obtained at 60 cm. When an unknown emf was connected, the balance was obtained at 82 cm. The magnitude of unknown emf is
Answer: A
.
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To increase Q factor of a coil, the wire should be
Answer: C
Q is high if resistance is low. Therefore, wire should be thick.
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A dynamometer wattmeter is connected in ac circuit. The reading will be
Answer: B
Wattmeter measures average power over a cycle.
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In which of the transformer is the secondary nearly short circuited under normal operating conditions?
Answer: A
CT is operated with secondary short-circuited otherwise a high emf would be induced across secondary.
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Which of the following is true about an impulse voltage?
Answer: A
Impulse is unidirectional (either positive or negative).
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The Lissajous pattern observed on screen of CRO is a straight line inclined at 45° to x axis. If X-plate input is 2 sin ωt, the Y-plate input is
Answer: B
When signals to X and Y plates are in phase, the display is a straight line inclined at 45°.
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In a ballistic galvanometer, a charge of 100 μC gives a first swing of 25°. The charge required to cause first swing of 50° is
Answer: B
swing is proportional to charge.
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