Internal Resistance(r) of a cell depends on 

i)The distance between the plates $\left(\mathrm{r} \mathrm{\alpha } \mathrm{d}\right)$

ii)The area and size of the plates $\left(\mathrm{r} \mathrm{\alpha } \frac{1}{\mathrm{A}}\right)$

iii)Nature of electrolyte

iv)Strength of the electrolyte (or) concentration $\left(\mathrm{r} \mathrm{\alpha } \mathrm{C}\right)$

v)Area of cross section f the electrolyte through which current flows

vi)It depends on temperature. It decreases with increase of temperature.