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Electronics and Communication Engineering - Electronic Devices and Circuits

Exercise : Electronic Devices and Circuits - Section 3
16.
Consider the following features of an instrument
  1. suitable for both ac and dc
  2. free from hysteresis and eddy current errors
  3. No waveform and frequency errors
  4. it is essentially a voltmeter
This instrument is
moving iron
moving coil
electrostatic
dynamometer
Answer: Option
Explanation:

Only electrostatic instrument has all these features.

17.
Which one of the following effects is used in measuring power?
Seeback
Ferrari
Induction
Hall
Answer: Option
Explanation:

Induction wattmeter.

18.
The effect of lead resistance is important in measurement of
resistance of shunt
resistance of shunt winding
resistance of ammeter
both (a) and (c)
Answer: Option
Explanation:

Lead resistance is important when measuring low resistance. Resistance of shunt and ammeter is low.

19.
A high resistance was measured by loss of charge method. The voltmeter resistance was 1010 ohms. The calculation gave the value of unknown resistance as 0.8 x 109 ohms. The true value of resistance is
0.8 x 109 Ω
less than 0.8 x 109 Ω
more than 0.8 x 109 Ω
either (b) or (c)
Answer: Option
Explanation:

Let unknown resistance be R.

Evidently R is more than 0.8 x 109 ohm.

20.
A resistance wire strain gauge has gauge factor 2. If stress is 100 mega newton/m2 and Young's modulus is 200 giga newton/ m2, the percentage change in gauge resistance due to stress is
0.1
0.2
0.4
0.5
Answer: Option
Explanation:

.

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