If reference sound pressure P0 is 2 x 10-5 N/m2, a sound pressure of 90 dB is eq

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Question
If reference sound pressure P₀ is 2 x 10^-5 N/m², a sound pressure of 90 dB is equal to
Options
A. 0.632 N/m²
B. 0.707 N/m²
C. 0.835 N/m²
D. 0.925 N/m²

Correct Answer

0.632 N/m²

Explanation

If reference sound pressure P0 is 2 x 10-5 N/m2, a sound pressure of 90 dB is equal to 0.632 N/m2 0.

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Measurements and Instrumentation problems

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1. 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
Options
A. 1200 revolutions
B. 1800 revolutions
C. 2100 revolutions
D. 2400 revolutions

2. In which of the transformer is the secondary nearly short circuited under normal operating conditions?
Options
A. CT
B. PT
C. Distribution transformer
D. Power transformer

3. Assertion (A): When a wattmeter is used for low impedance loads, the pressure coil is connected across the load.
Reason (R): A wattmeter measures apparent power.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true R is false
D. A is false R is true

4. A digital frequency counter can be converted to DVM by addition of a suitable
Options
A. voltage controlled oscillator
B. D/A converter
C. power amplifier
D. operational amplifier

5. In a thermocouple temperature transducer, the output voltage is usually measured by
Options
A. high resistance ammeter
B. high resistance voltmeter
C. high resistance milli-voltmeter
D. none of the above

6. Assertion (A): A hot wire ammeter has a cramped scale.
Reason (R): The heat is proportional to square of current.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true R is false
D. A is false R is true

7. Consider the following statements: In a differential amplifier using JFET, the differential output offset is due to
1. mismatch between FET parameters
2. difference in values of resistances used in circuit
3. variation in supply voltage.
Of the statements, the correct statements are
Options
A. 1 and 2
B. 1, 2, 3
C. 2, 3
D. 1, 3

8. A full wave rectifier type meter is used to measure the wave shape shown in figure. The voltmeter is calibrated to read rms value of sine wave. The reading of voltmeter will be
Options
A.
B.
C. 100 V
D. 111 V

9. A moving iron instrument gives correct reading when used at
Options
A. low frequencies
B. high frequencies
C. only one frequency
D. all frequencies upto a certain value

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