Measurement and Instrumentation
The meter constant of a single phase 240 V induction watthour meter is 400 revolutions per KWh. The speed of the meter disc for a current of 10 Amperes of 0.8 p.f lagging will be

 21.1 rpm.
 18.2 rpm.
  12.8 rpm.
 16.02 rpm.

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Measurement and Instrumentation
Assertion (A) : It is always desirable to take the reading of an indicating instrument very close to the full scale reading. Reason (R) : Accuracy of an indicating instrument is maximum at the full scale deflection and error increases as reading comes closer to the beginning of the scale.

 Both A and R are true but R is NOT the correct explanation of A
 Both A and R are true and R is the correct explanation of A
 A is true but R is false
 A is false bur R is true

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