Measurement and Instrumentation
Which of following statement are correct in case of power factor meter?

 Both B and C.
 The deflection is proportional to phase angle between field coil and crossed coil.
 The restoring torque is provided by a controlling torque.
 It consist of two coils mounted at right angles to each other.

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Measurement and Instrumentation
In DC potentiometer measurments, a second reading is often taken after reversing the polarities of the DC supply and the unknown voltage and the average of the two reading is taken. This is with a view of eliminate the effects of

 Stray magnetic fields.
 Errorneous standardisation.
  Stray thermal emfs.
 Ripples of the DC supply.

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