The combination of two identical cells, whether connected in series or parallel combination provides the same current through an external resistance of 2 Ω . The value of internal resistance of each cell is

Step-by-step solution

When the cells are connected in series i s = 2 ε 2 r + R = 2 ε 2 r + 2 When they are connected in parallel, the emf is ε p = ε r + ε r 1 r + 1 r = ε and the effective internal resistance will be r p = r × r r + r = r 2 . Therefore, the current will be, i p = ε R + r 2 = ε 2 + r 2 = 2 ε 4 + r Since, i s = i p ⇒ 2 ε 2 r + 2 = 2 ε 4 + r ⇒ r = 2   Ω