Two identical cells each of emf $1.5\,V$ are connected in series across a $10\,\Omega$ resistance. An ideal voltmeter connected across $10\,\Omega$ resistance reads $1.5\,V$. The internal resistance of each cell is $......\Omega$.
A$5$
B$10$
C$15$
D$20$
JEE MAIN 2023, Medium
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A$5$
a $V = I \times 10$
$1.5=\left(\frac{3}{10+2 r }\right) \times 10$
$r =5\,\Omega$
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