Two identical cells each of emf 1 . 5 V are connected in series across a 10 Ω resistance. An ideal voltmeter connected across 10 Ω resistance reads 1 . 5 V . The internal resistance of each cell is _____ Ω .

Step-by-step solution

Let R 1 = 10   Ω . Using V = i R i = 3 10 + 2 r The voltmeter reading is V ' = 1 . 5   V . Thus, i R 1 = V ' ⇒ 10 × 3 10 + 2 r = 1 . 5 ⇒ 20 = 10 + 2   r ⇒ 2 r = 10 ⇒ r = 5   Ω