Measurement and Instrumentation
Potentiometer method of DC voltage measurement is more accurate than direct measurement using a voltmeter because

 It loads the circuit to maximum extent.
  It does not load the circuit at all.
 It loads the circuit moderately.
 It uses centre zero galvanometer instead of voltmeter.

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Measurement and Instrumentation
A Manganin swap resistance is connected in series with a moving coil ammeter consisting of a milli ammeter and a suitable shunt in order to

 Minimize the effect of stray magnetic fields.
 Obtaine large deflecting torque.
  Minimize the effect of temperature variation.
 Reduce the size of the meter.

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