The two ends of a uniform conductor are joined to a cell of emf $\epsilon$ and some internal resistance. Starting from the midpoint P of the conductor, we move in the direction of the current and return to P. The potential V at every point on the path is plotted against the distance covered (x). Which of the following best represents the resulting curve ?

When we move in the direction of the current in a uniform conductor, the potential difference decreases linearly. When we pass through the cell, from its negative to its positive terminal, the potential increase by an amount equal to its potential difference. This is less than its emf, as there is some potential drop across its internal resistance when the cell is driving current.