(3 42) would change to VBC = –e2–Ir2 and we will get
eeq = e1 – e2         (e1 > e2)
(3 47)
The rule for series combination clearly can be extended to any number
of cells:
(i)
The equivalent emf of a series combination of n cells is just the sum of
their individual emf’s, and
(ii) The equivalent internal resistance of a series combination of n cells is
just the sum of their internal resistances This is so, when the current leaves each cell from the positive
electrode