Grouping Of Cells

When identical cells are joined in series, their EMFs add and their internal resistances also add, so the group behaves as a single source of EMF (n\varepsilon) and internal resistance (nr). For three cells the total EMF is (3 \times 1.5 = 4.5) V and the combined internal resistance is (3 \times 0.2 = 0.6;\Omega). The circuit current then follows from (I = \frac{n\varepsilon}{R + nr} = \frac{4.5}{4.4 + 0.6} = \frac{4.5}{5.0} = 0.9) A. The value 1.5 A ignores both the internal resistances and the series addition of EMFs. The value 0.45 A wrongly halves the source EMF. The value 0.3 A treats only a single cell's EMF across the full resistance. This applies the NCERT result for cells grouped in series. A plausibility check confirms it: the combined internal resistance (0.6 (\Omega)) is small beside the load, so almost the full 4.5 V drives the current, giving close to but slightly below (4.5/4.4) A, consistent with 0.9 A. It is worth contrasting this with a parallel grouping of the same cells, which would instead keep the EMF at a single 1.5 V while reducing the effective internal resistance; the series arrangement is therefore the right choice when the external resistance is large and a higher driving voltage is needed.