Question

Find the emf and the internal resistance of a source which is equivalent to two batteries connected in parallel whose emf's are equal to emf(ℰ₁) and emf(ℰ₂) and internal resistances to R₁ and R₂.

Answer 1

Let us connect a load of resistance K between the points A and B (Fig.)

From the loop rule, Δ φ = 0, we obtain

Thus one can replace the given arrangement of the cells by a single cell having the emf ℰ₀ and internal resistance R₀ .