For the two cells having same EMF E and internal resistance r, the current passing through the external resistor 6 Ω is same when both the cells are connected either in parallel or in series. The value of internal resistance r is 3em Ω. (a) 3 (b) 6 (c) 4 (d) 9

Answer: (b). Series: I = (2E)/(6 + 2r); parallel: I = (E)/(6 + r/2) Equal: 2(6 + r/2) = 6 + 2r ⇒ 12 + r = 6 + 2r r = 6 Ω. So the answer is (b) 6.

For the two cells having same EMF E and internal resistance r, the… | JEE Main 2026 (28 Jan, Shift 1)

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Cells: EMF, Internal Resistance & Combinations

For the two cells having same EMF $E$ and internal resistance $r$ , the current passing through the external resistor $6\ \Omega$ is same when both the cells are connected either in parallel or in series. The value of internal resistance $r$ is $\underline{\hspace{3em}}\ \Omega$ .

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Answer: (b)

Series: $I = \frac{2E}{6 + 2r}$ ; parallel: $I = \frac{E}{6 + r/2}$
Equal: $2\left(6 + \frac{r}{2}\right) = 6 + 2r \Rightarrow 12 + r = 6 + 2r$
$r = 6\ \Omega$ . So the answer is (b) 6.

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