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 If in the combination, the current leaves any cell from
the negative electrode, the emf of the cell enters the expression
for eeq with a negative sign, as in Eq