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Electronics and Communication Engineering - Measurements and Instrumentation

Exercise : Measurements and Instrumentation - Section 3
36.
A resistance is measured by voltmeter-ammeter method. The voltmeter is 0-250V, ± 1% accuracy and ammeter is 0-5 A, ± 1 % accuracy. The readings of voltmeter and ammeter are 100 V and 2 A respectively. The error in the measured resistance can be
± 1%
± 2%
± 5%
± 10%
Answer: Option
Explanation:

Error in voltmeter can be ± 2.5 V which for 100 V reading is ± 2.5 % . Error in ammeter can be ± 0.05 A which for 2 A reading is ± 2.5 %. Hence total error can be ± 5%.

37.
It is required to study transients during switching process. Which CRO should be preferred?
Ordinary CRO
Dual beam CRO
Dual trace CRO
Storage oscilloscope
Answer: Option
Explanation:

We can store the trace.

38.

Assertion (A): In loss of charge method, it is preferable to use an electronic voltmeter.

Reason (R): The resistance of electronic voltmeter is very high.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not correct explanation of A
A is true R is false
A is false R is true
Answer: Option
Explanation:

If resistance of voltmeter is not high, accuracy is affected.

39.
If the secondary winding of CT is opened when primary coil is carrying current
transformer will burn immediately
there will be weak flux density in core
there will be very high induced voltage in secondary
there will be high current in secondary
Answer: Option
Explanation:

Since the primary of CT always remains excited, a high voltage is induced in secondary if the secondary is opened.

40.
The percentage limiting error in an instrument reading 8.3 V and having guaranteed accuracy of 1% of the full scale reading and range of 0-150 V is
1.81%
0.181%
18.1%
0.0018%
Answer: Option
Explanation:

Error = 1% of 150 = 1.5 V,

.

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