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Electronics and Communication Engineering - Measurements and Instrumentation

Exercise : Measurements and Instrumentation - Section 4
46.
Hay's bridge is suitable for inductances having low L/R ratio.
True
False
Answer: Option
Explanation:

It is suitable for high ratio inductances.

47.
Moving iron instrument can be used for ac only.
True
False
Answer: Option
Explanation:

Moving iron instruments can be used for both dc and ac.

48.
In electronic voltmeters the measuring device is a
moving coil instrument
moving iron instrument
dynamometer instrument
none of the above
Answer: Option
Explanation:

The a.c. voltage is rectified and measured by PMMC instrument.

49.
An ammeter has a resistance of 50 ohms and a shunt of 0.01 Ω. The deflection is θ. If the shunt resistance is increased to 0.02 Ω, the deflection will be.
θ
2θ
0.5θ
0.25θ
Answer: Option
Explanation:

Since shunt resistance is doubled, current through ammeter is doubled (current division for resistances in parallel). Therefore reading is 2 θ.

50.
The ac bridge in figure is balanced. Z1 = 100∠30°, Z2 = 150∠0°, Z3 = 250∠ - 40° Then Z4 =
375∠70° Ω
375∠ - 70° Ω
150∠0° Ω
150∠20° Ω
Answer: Option
Explanation:

.

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