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Electronics and Communication Engineering - Measurements and Instrumentation

Exercise : Measurements and Instrumentation - Section 1
16.
In figure, Z1 = 200∠60° Ω, Z2 = 400∠ - 90° Ω, Z3 = 300∠0°. Then Z4 for bridge to be balanced is
150∠30° Ω
400∠ - 90° Ω
300∠90° Ω
600∠ - 150° Ω
Answer: Option
Explanation:

.

17.
In a ballistic galvanometer, a charge of 100 μC gives a first swing of 25°. The charge required to cause first swing of 50° is
200 μC
400 μC
50 μC
25 μC
Answer: Option
Explanation:

swing is proportional to charge.

18.
Two resistors R1 = 36 Ω ± 5% and R2 = 75 Ω ± 5% are connected in series. The total resistance is
111 ± 0 Ω
111 ± 2.778 Ω
111 ± 5.55 Ω
111 ± 7.23 Ω
Answer: Option
Explanation:

Total maximum error ± (1.8 + 3.75) = ± 5.55 Ω.

19.
Figure shows an RC potentiometer to measure ac voltage. It is desired that V0/Vi should be independent of frequency. The value of C should be
10 μF
11 μF
0.1 μF
0.09 μF
Answer: Option
Explanation:

Since resistances are in the ratio of 10 : 1, capacitances should be in the ratio of 1 : 10 because XC ∝ 1/C.

20.
In a strain measuring device using a strain gauge, the output quantity is
voltage
resistance
impedance
either (a) or (b)
Answer: Option
Explanation:

The measurement is done using an unbalanced bridge.

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