Two identical cells, when connected either in parallel or in series gives same current in an external resistance 5 Ω. The internal resistance of each cell will be ___________ Ω. Numerical answer type. Work it out, then open the answer.

Answer: 5. Series: Is = (2E)/(5 + 2r); parallel: Ip = (E)/(5 + r/2). Is = Ip ⇒ 2(5 + r/2) = 5 + 2r 10 + r = 5 + 2r ⇒ r = 5 Ω

Two identical cells, when connected either in parallel or in series… | JEE Main 2023 (31 Jan, Shift 1)

Q17JEE Main 2023 · 31 JAN · SHIFT 1Medium

Cells: EMF, Internal Resistance & Combinations

Two identical cells, when connected either in parallel or in series gives same current in an external resistance $5\ \Omega$ . The internal resistance of each cell will be ___________ $\Omega$ .

Numerical answer type. Work it out, then open the answer.

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Answer: 5

Series: $I_s = \dfrac{2E}{5 + 2r}$ ; parallel: $I_p = \dfrac{E}{5 + r/2}$ .
$I_s = I_p \Rightarrow 2(5 + r/2) = 5 + 2r$
$10 + r = 5 + 2r \Rightarrow r = 5\ \Omega$

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