181. A volt-ratio box is designed with a resistance 100 Ω/V. It has input terminals of 300 V, 150 V and 75 V, and an output terminal of 1.5 V which is connected to the potentiometer. Supposing a voltage of 270 V is connected to 300 V terminal, what is voltage indicated by the potentiometer and what is the power consumption under null condition?

1. 1. 1.5 V, 3 W

   
   
   

   2. 1.35 V, 3 W

   
   
   

   3. 1.5 V, 2.43 W

   
   
   

   4. 1.35 V, 2.34 W

   
   
   

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   NA

   Correct Option: D

   NA

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182. Standardization of potentiometers is done in order that, they become

1. 1. accurate

   
   
   

   2. precise

   
   
   

   3. accurate and direct reading

   
   
   

   4. accurate and precise

   
   
   

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   NA

   Correct Option: C

   NA

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183. When a potentiometer is used for measurement of voltage of an unknown source, the power consume in the circuit of the unknown source under null conditions is

1. 1. very high

   
   
   

   2. high

   
   
   

   3. small
      

   
   
   

   4. ideally zero

   
   
   

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   NA

   Correct Option: D

   NA

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184. In a Kelvin’s Double Bridge, two sets of readings are taken when measuring a low resistance, one with the current in one direction and the other with direction of current reversed. This is done to eliminate the effect of
     

1. 1. contact resistance

   
   
   

   2. resistance of leads

   
   
   

   3. changes in battery voltage

   
   
   

   4. thermo-electric emfs

   
   
   

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   NA

   Correct Option: D

   NA

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185. A Wheatstone bridge cannot be used for precision measurements because errors are introduced into on account of

1. 1. resistance of connecting leads

   
   
   

   2. thermo-electric emfs

   
   
   

   3. contact resistances

   
   
   

   4. all of these

   
   
   

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   NA

   Correct Option: D

   NA

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