CBSE Class 12 · 2008 · Current ElectricityShort Answer

From $V=E_{\text{total}}-i{r}_{\text{total}}$, the $V$-intercept ($i=0$) gives the total EMF of the three series cells, so each cell's EMF is one-third of it; the magnitude of the slope gives the total internal resistance $r_{\text{total}}$. The power in the external load $P=i^{2}R$ is maximum under matching ($R=r_{\text{total}}$), when the current is half the short-circuit current: $I=\frac{E_{\text{total}}}{2r_{\text{total}}}$.