Two cells of emfs 1 V and 2 V and internal resistance 2 Ω and 1 Ω… | JEE Main 2026 (6 Apr, Shift 2)

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Cells: EMF, Internal Resistance & Combinations

Two cells of emfs 1 V and 2 V and internal resistance $2\ \Omega$ and $1\ \Omega$ , respectively connected in parallel, gave a current of 1 A through an external resistance. If the polarity of one cell is reversed, then value of current through the external resistance will be $\frac{\alpha}{5}\text{ A}$ . The value of $\alpha$ is ______.

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

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Answer: 3

Parallel cells: $E_{eq} = \dfrac{E_1/r_1 + E_2/r_2}{1/r_1 + 1/r_2}$ , $r_{eq} = \dfrac{r_1 r_2}{r_1 + r_2} = \dfrac{2}{3}\ \Omega$ .
Same polarity: $E_{eq} = \dfrac{1/2 + 2/1}{3/2} = \dfrac{5}{3}\text{ V}$ ; $1 = \dfrac{5/3}{R + 2/3} \Rightarrow R = 1\ \Omega$ .
One cell reversed: $E_{eq} = \dfrac{-1/2 + 2/1}{3/2} = 1\text{ V}$ .
$I = \dfrac{1}{1 + 2/3} = \dfrac{3}{5}\text{ A} \Rightarrow \alpha = 3$

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Cells: EMF, Internal Resistance & Combinations question from JEE Main 2026 (6 Apr, Shift 2)

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