When we are measuring the internal resistance of a cell by a potentiometer, the e.m.f of the battery must be greater than the:

Explanation

The emf of the battery in the potentiometer experiment should be greater than the emf of the cell to be determined because The fall of potential across the potentiometer wire should not be less than the emf of the cell to be determined. And the potential across the wire is determined by the emf of the battery. If either the emf of the battery or the potential difference across the whole potentiometer wire is lesser than the emf of the experimental cell, the balance point will not be obtained. The balance point indicates that the emf of the cell to be determined is just balanced by the voltage drop that appears across the wire.