Question

Two sources of current of equal emf are connected in series and have different internal resistances R₁ and R₂ (R₂ > R₁). Find the external resistance R at which the potential difference across the terminals of one of the sources (which one in particular?) becomes equal to zero?

Answer 1

Let, us consider the current i, flowing through the circuit, as shown in the figure. Applying loop rule for the circuit, - Δ φ = 0

So, R = R₁ - R₂, which is the required resistance.