Questions 631–640 of 650. Imported answers require independent review unless marked reviewed.

Topic practice 650 questionsPage 64 of 65

Question 46

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The power delivered to a single phase inductive load is measured with a dynamometer type wattmeter using a potential transformer (PT) of turns ratio 200:1 and the current transformer (CT) of turns ratio 1:5. Assume both the transformers to be ideal. The power factor of the load is 0.8. If the wattmeter reading is 200 W, then the apparent power of the load in kVA is __________.

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Question 47

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The unbalanced voltage of the Wheatstone bridge, shown in the figure,
Diagram for Instrumentation Engineering question 47

is measured using a digital voltmeter having infinite input impedance and a resolution of 0.1 mV. If

, then the minimum value of

in

to create a detectable unbalanced voltage is __________.

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Question 48

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In the a.c. bridge, shown in the figure,

and

. If the bridge is balanced at a frequency

, the value of

in rad/s is ________.
Diagram for Instrumentation Engineering question 48


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Question 49

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The hot junction of a bare thermocouple, initially at room temperature (30°C), is suddenly dipped in molten metal at

s. The cold junction is kept at room temperature. The thermocouple can be modeled as a first-order instrument with a time constant of 1.0 s and a static sensitivity of 10 μV/°C. If the voltage, measured across the thermocouple indicates 10.0 mV at

s, then the temperature of the molten metal in °C is ________.

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Question 50

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A resistance temperature detector (RTD) is connected to a circuit, as shown in the figure. Assume the opamp to be ideal. If

, then the value of

is ________.
Diagram for Instrumentation Engineering question 50


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Question 51

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The magnetic flux density of an electromagnetic flowmeter is 100 mWb/m². The electrodes are wall-mounted inside the pipe having a diameter of 0.25 m. A voltage of 1 V is generated when a conducting fluid is passed through the flowmeter. The volumetric flowrate of the fluid in m³/s is ________.

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Question 52

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The junction semiconductor temperature sensor shown in the figure is used to measure the temperature of hot air. The output voltage

is 2.1 V. The current output of the sensor is given by

where

is the temperature in K. Assuming the opamp to be ideal, the temperature of the hot air in °C is approximately ________.
Diagram for Instrumentation Engineering question 52


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Question 53

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Quantum efficiency of a photodiode (ratio between the number of liberated electrons and the number of incident photons) is 0.75 at 830 nm. Given Planck’s constant

, the charge of an electron

and the velocity of light in the photodiode

. For an incident optical power of 100 μW at 830 nm, the photocurrent in μA is ________.

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Question 54

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In a sinusoidal amplitude modulation scheme (with carrier) the modulated signal is given by

, where

is the carrier frequency and

is the modulation frequency. The power carried by the sidebands in % of total power is ________%.

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Question 55

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An angle modulated signal with carrier frequency

rad/s is given by

. The maximum deviation of the frequency in the angle modulated signal from that of the carrier is ________ kHz.

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