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Electronics and Communication Engineering - Measurements and Instrumentation

Exercise : Measurements and Instrumentation - Section 2
21.

Assertion (A): Wien bridge can be used for measuring frequency.

Reason (R): A frequency meter for 50 Hz system has a frequency range of 40 to 60 Hz.

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:

Frequency range is 47 to 53 Hz.

22.
Which of these has poor overload capacity?
PMMC instrument
Hot wire instrument
Dynamometer instrument
Both (a) and (c)
Answer: Option
Explanation:

The wire is very delicate and has little over load capacity.

23.
In 3 phase power measurement by two wattmeter method, both wattmeters had equal reading. The power factor of load is
1
0.5 lagging
0.5 leading
0
Answer: Option
Explanation:

Readings of two wattmeters are same when σ = 0 or p.f. = 1.

24.
Which instrument is based on induction principle?
Dynamometer wattmeter
Induction wattmeter
Energy meter
Both (b) and (c)
Answer: Option
Explanation:

Energy meter is also based on induction principle.

25.
Magnetic field intensity has the dimensions
IL
I2L
IL-1
IL-2
Answer: Option
Explanation:

Magnetic field intensity = MMF/length = IL-1.

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