Electronics and Communication Engineering - Measurements and Instrumentation

6. 

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

A. 0.632 N/m2
B. 0.707 N/m2
C. 0.835 N/m2
D. 0.925 N/m2

Answer: Option A

Explanation:

.


7. 

Which of the following voltmeters would you use for measuring voltage across 20 kΩ resistance?

A. Voltmeter having a resistance of 5 kΩ
B. Voltmeter having a sensitivity of 1 kW/V
C. Voltmeter having sensitivity of 10 kW/V
D. None of the above

Answer: Option C

Explanation:

Resistance of voltmeter should be very high as compared to 20 kΩ.


8. 

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

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

Answer: Option D

Explanation:

0.5 x 4 = 2 kWh = 2 x 1200 revolutions.


9. 

Assertion (A): De sauty's bridge is suitable only for pure capacitor.

Reason (R): Capacitors are mostly perfect.

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

Answer: Option C

Explanation:

Capacitors are mostly imperfect.


10. 

In which of the transformer is the secondary nearly short circuited under normal operating conditions?

A. CT
B. PT
C. Distribution transformer
D. Power transformer

Answer: Option A

Explanation:

CT is operated with secondary short-circuited otherwise a high emf would be induced across secondary.