Two cells of emfs $\epsilon_1$ and $\epsilon_2$ and internal resistances $r_1$ and $r_2$ are connect

Question

Two cells of emfs $\epsilon_1$ and $\epsilon_2$ and internal resistances $r_1$ and $r_2$ are connected in parallel. What is the equivalent emf ($\epsilon_{eq}$) of the combination?

Professor PC Thomas Classes · Answer

For a parallel combination of two cells, the equivalent emf is given by $\epsilon_{eq} = (\epsilon_1 r_2 + \epsilon_2 r_1) / (r_1 + r_2)$.