Physics - Current Electricity Question with Solution | TestHub

Given : Number of cells, $n=5$, emf of each cell $=E$ Internal resistance of each cell $=r$ In series, current through resistance $R$ $I=\frac{nE}{nr+R}=\frac{5E}{5r+R}$ In parallel, current through resistance $R$ $I^{\prime }=\frac{E}{\frac{r}{n}+R}=\frac{nE}{r+nR}=\frac{5E}{r+5R}$ According to question, $I=I^{\prime }$ $\therefore \frac{5E}{5r+5R}=\frac{5E}{r+5R}\Rightarrow 5r+R=r+5R$ or $R=r\therefore \frac{R}{r}=1$