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Electronics and Communication Engineering - Measurements and Instrumentation

Exercise : Measurements and Instrumentation - Section 4
6.
The most commonly used moving iron instruments are
repulsion type
attraction type
a combination of attraction and repulsion type
none of the above
Answer: Option
Explanation:

Repulsion type have better accuracy.

7.
A moving iron instrument can be used for
dc only
ac only
both dc and ac
dc and high frequency ac
Answer: Option
Explanation:

Its deflecting torque ∝ I2. So, it can be used for both d.c. and a.c.

8.
Two voltmeters are each 0-300 V range. Their internal resistances are 10 kΩ and 20 kΩ They are connected is series and a voltage of 400 V is applied. Their readings respectively will be
266.6 and 133.3 V
133.3 and 266.6 V
200 V each
100 and 300 V
Answer: Option
Explanation:

The readings will be proportional to their internal resistance,

.

9.
A 300 V voltmeter has an accuracy of ± 2% of full scale deflection. When the reading is 222 V, the actual voltage
lies between 217.56 and 226.44 V
lies between 217.4 and 226.6 V
lies between 216 and 228 V
is exact 222 V
Answer: Option
Explanation:

Error = ± 6 V. Therefore, the actual value would be between 222 ± 6 V.

10.
In a thermocouple two metal junctions between metals M1 and M2 are kept at temperature T1 and T2. The thermocouple emf is produced because
M1, M2 are similar and T1, T2 are equal
M1, M2 are similar but T1, T2 are unequal
M1, M2 are dissimilar but T1, T2 are equal
M1, M2 are dissimilar but T1, T2 are unequal
Answer: Option
Explanation:

The two materials in thermocouple are different and the two junctions are kept at different temperatures.

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