If m identical cells of e.m.f. V and internal resistance 'r' are connected in series, they produce a current through an external resistance R equal to
1
\(\frac{{{\rm{mV}}}}{{{\rm{r}} + {\rm{R}}}}\)
2
\(\frac{{{\rm{mV}}}}{{\rm{R}}}\)
3
\(\frac{{\rm{V}}}{{{\rm{r}} + {\rm{R}}}}\)
4
\(\frac{{{\rm{mV}}}}{{{\rm{mr}} + {\rm{R}}}}\)