31. A 0 – 300 V voltmeter has an error of ± 2% of full scale deflection. If true voltage is 30 V, the range of readings will be

1. 1. 24 V – 36 V

   
   
   

   2. 29.4 V – 30.6 V

   
   
   

   3. 20 V to 40 V

   
   
   

   4. none of these

   
   
   

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   NA

   Correct Option: A

   NA

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32. An 0 – 10 A ammeter has guaranteed accuracy of 1 percent of full scale deflection. The limiting error while reading 2.5 is

1. 1. 1%

   
   
   

   2. 2%

   
   
   

   3. 4%

   
   
   

   4. none of these

   
   
   

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   NA

   Correct Option: C

   NA

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33. The power in a 3-phase, 3-wire load is measured using two 100W full-scale wattmeters W₁ and W₂. W₁ is of a accuracy class ± 1% and reads 100 W. W₂ is of accuracy class ± 0.5% and reads – 50 W. Then the uncertainty in the computation to total power is

1. 1. ± 1.5%

   
   
   

   2. ± 0.5%

   
   
   

   3. ± 4%

   
   
   

   4. ± 3%

   
   
   

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   W₁ = 100W + 1W;
   W₂ = – 50 + 0.5W
   

   ∴ W1 + W2 =		50 ±	1.5		× 100 = ± 3%
   			50

   Correct Option: D

   W₁ = 100W + 1W;
   W₂ = – 50 + 0.5W
   

   ∴ W1 + W2 =		50 ±	1.5		× 100 = ± 3%
   			50

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34. The high torque to weight ratio in an analog indicating instrument indicates

1. 1. high friction loss

   
   
   

   2. low friction loss

   
   
   

   3. nothing as regards friction loss

   
   
   

   4. none of these

   
   
   

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   NA

   Correct Option: B

   NA

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35. A PMMC instrument produces a deflection of 90° when a current 2 mA passes through its moving coil. The instrument is spring controlled. Supposing the instrument is redesigned with its spring constant as before, and its permanent magnet is replaced with a new permanent magnet which reduces twice the flux density as before, what would be the deflection if a current of 1 mA is passed through the coil? The other features of the PMMC instrument remain the same.

1. 1. 180°

   
   
   

   2. 90°

   
   
   

   3. 45°

   
   
   

   4. 135°

   
   
   

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   NA

   Correct Option: B

   NA

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