AIIMS 2018 Physics Batteries in Parallel MCQ Question

In a parallel configuration of batteries, the equivalent electromotive force (emf) is determined by the battery with the highest voltage, while the internal resistance is calculated using the formula $r = \frac{r_1 r_2}{r_1 + r_2}$, which is indeed less than either $r_1$ or $r_2$. Option (A) incorrectly suggests a formula for emf that does not apply to parallel circuits, as it implies a dependency on both battery voltages and resistances in a way that is not valid. Option (B) correctly identifies the formula for internal resistance but does not address the emf, making it incomplete. Thus, option D is the only choice that accurately reflects the principles governing parallel battery configurations.