Two cells, having the same emf, are connected in series through an external resistance R. Cells have internal resistances r₁ and r₂ (r₁ r₂) respectively. When the circuit is closed, the potential difference across the first cell is zero. The value of R is :

Question

Two cells, having the same emf, are connected in series through an external resistance R. Cells have internal resistances r₁ and r₂ (r₁ > r₂) respectively. When the circuit is closed, the potential difference across the first cell is zero. The value of R is :

Dr. Abubacker · Accepted Answer

[Solution from source] The current is I = 2E/(R + r₁ + r₂). The p.d. across the first cell is E − Ir₁ = 0, so I = E/r₁. Equating: 2r₁ = R + r₁ + r₂, giving R = r₁ − r₂. Setting the second cell's p.d. to zero would give r₂ − r₁, which is negative here. Answer (1).

Q. Two cells, having the same emf, are connected in series through an external resistance R. Cells have internal resistances r₁ and r₂ (r₁ > r₂) respectively. When the circuit is closed, the potential difference across the first cell is zero. The value of R is :

Explanation

Reviewed by Dr. Abubacker

Want to attempt the full paper?