A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of $2.0\mathrm{ }\mathrm{V}$ and a negligible internal resistance. The potentiometer wire itself is $4\mathrm{ }\mathrm{m}$ long. When the resistance, $R,$ connected across the given cell, has values of.
$\left(\mathrm{i}\right)$ infinity $\left(\mathrm{i}\mathrm{i}\right) 9.5 \mathrm{\Omega }$
The 'balancing lengths, on the potentiometer wire are found to be $3\mathrm{m}$ and $2.85\mathrm{ }\mathrm{m},$ respectively. The value of internal resistance of the cell is: