Explanation:
\({\mathop{\rm Here}\nolimits} ,\,\,\,\,mn = 20\,\,\,\,\,\,\,\,\,\,\,(1)\)
For maximum current \(R = \frac{{nr}}{m}\)
\(2.5 = n \times \frac{{0.5}}{m}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(2)\)
From Eq’s (1) & (2) we get
\(m = 2,\;{\rm{and}}\;n = 10\)