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Two identical cells each of emf 1.5 V are connected in parallel across a parallel combination of two resistors each of resistance 20 Ω. A voltmeter connected in the circuit measures 1.2 V. The internal resistance of each cell is

Asked in JEE Main 24th June 1st Shift 2022 · Combination of cells

Answer: (3) 5 Ω

Step-by-step solution

Two identical cells in parallel: E_eq=1.5 V, r_eq=r/2.

Load: 20∥20=10 Ω; terminal voltage 1.2 V gives I=(1.2)/(10)=0.12 A.

E-V=Ir_eq⇒ 0.3=0.12×r/2

r=5 Ω

Why the other options are wrong

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