$I_{1}=\frac{\varepsilon_{2}-V}{r_{1}} \Rightarrow I_{2}=\frac{\varepsilon_{2}-V}{r_{2}}$
Combining the last three equations
$\mathrm{I}=\mathrm{I}_{1}+\mathrm{I}_{2}=\frac{\varepsilon_{1}-\mathrm{V}}{\mathrm{r}_{1}}+\frac{\varepsilon_{2}-\mathrm{V}}{\mathrm{r}_{2}}$
$=\left(\frac{\varepsilon_{1}}{\mathrm{r}_{1}}+\frac{\varepsilon_{2}}{\mathrm{r}_{2}}\right)-\mathrm{V}\left(\frac{1}{\mathrm{r}_{1}}+\frac{1}{\mathrm{r}_{2}}\right)$
Hence, $\mathrm{V}$ is given by, $\mathrm{V}=\frac{\varepsilon_{1} \mathrm{r}_{2}+\varepsilon_{2} \mathrm{r}_{1}}{\mathrm{r}_{1}+\mathrm{r}_{2}}-\mathrm{I} \frac{\mathrm{r}_{1} \mathrm{r}_{2}}{\mathrm{r}_{1}+\mathrm{r}_{2}}$
If we want to replace the combination by a single cell, between $\mathrm{B}_{1}$ and $\mathrm{B}_{2}$ of emf $\varepsilon_{\mathrm{eq}}$ and internal resistance $\mathrm{r}_{\mathrm{eq}},$
we would have $\mathrm{V}=\varepsilon_{\mathrm{eq}}-\mathrm{Ir}_{\mathrm{eq}}$
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| List - $I$ | List - $II$ |
| $P.\quad$ Lift is accelerating vertically up. | $1.\quad$ $d=1.2 \ m$ |
| $Q.\quad$ Lift is accelerating vertically down with an accelerating less than the gravitational acceleration. | $2.\quad$ $d>1.2 \ m$ |
| $R.\quad$ List is moving vertically up with constant Speed | $3.\quad$ $d<1.2 \ m$ |
| $S.\quad$ Lift is falling freely. | $4.\quad$ No water leaks out of the jar |
