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Current Electricity — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsCurrent Electricity1 Mark
MCQ
A potentiometer can measure emf of a cell because:
  • A
    The sensitivity of potentiometer is large.
  • B
    No current is drawn from the cell at balance.
  • ✓
    No current flows in the wire of potentiometer at balance.
  • D
    Internal resistance of cell is neglected.
✓

Answer

Correct option: C.
No current flows in the wire of potentiometer at balance.

Potentiometer is preferred over voltmeter because it measures true emf of the cell. It uses null method so that no current is drawn from cell in balanced condition, as $E - Ir = V$ and $I = 0$ then $V = E.$
Hence emf measurement is more accurate.

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