156. Which one of the following types of indicating instruments is an electrometer?
     

1. 1. Electrodynamometer

   
   
   

   2. PMMC

   
   
   

   3. Electrostatic

   
   
   

   4. Moving iron

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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157. What will happen if a voltmeter is connected like an ammeter in series to the load?

1. 1. The meter will burn out

   
   
   

   2. The measurement will be too high

   
   
   

   3. An inadmissably high current will flow

   
   
   

   4. There will be almost no current in the circuit

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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158. A single-phase energymeter is operating on 230 V, 50 Hz supply with a load of 20 A for two hours at upf. The meter makes 1380 revolutions in that period. The meter constant is

1. 1. 695 rev/kWh

   
   
   

   2. 150 rev/kWh

   
   
   

   3. 0.15 rev/kWh

   
   
   

   4. 1/150 rev/kWh

   
   
   

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1. View Hint View Answer Discuss in Forum

   Energy consumed =	230 × 20 × 1 × 2	= 9.2kWh
   	1000

   
   Revolution made = 1380
   

   ∴ Meter constant =	1380	= 150 rev/kWh
   	9.2

   Correct Option: B

   Energy consumed =	230 × 20 × 1 × 2	= 9.2kWh
   	1000

   
   Revolution made = 1380
   

   ∴ Meter constant =	1380	= 150 rev/kWh
   	9.2

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159. A zero to 300 V voltmeter has an error of 12% of the full-scale deflection. If the true voltage is 30V, then the range of readings on this voltmeter would be
     

1. 1. 20 V to 40 V

   
   
   

   2. 24 V to 36 V

   
   
   

   3. 29.4 V to 30.6 V

   
   
   

   4. 29.94 to 30.06 V

   
   
   

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   Maximum possible error that can be present on any reading
   

   = 30 ×	2	= 0.6V
   	100

   
   Thus the voltmeter reading can be within 29.4 V to 30.6 V

   Correct Option: C

   Maximum possible error that can be present on any reading
   

   = 30 ×	2	= 0.6V
   	100

   
   Thus the voltmeter reading can be within 29.4 V to 30.6 V

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160. The resistance of a thermometer is 5Ω at 30°C and 6.5Ω at 60°C. Using linear approximation, the value of resistance temperature co-efficient at 45° is
     

1. 1. 0.009/°C

   
   
   

   2. 0.0087/°C

   
   
   

   3. 0.0085/°C

   
   
   

   4. 0.01/°C

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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