Question

In the given circuit, an ideal voltmeter connected across the $10\Omega$ resistance reads $2V$. The internal resistance $r$, of each cell is :

• A. $1\Omega$
• B. $1.5\Omega$
• C. $0\Omega$
• D. $0.5\Omega$

Answer 1

The correct option is D $0.5\Omega$

$R_{eq}=\frac{15\times 10}{25}+2+2r$
$=8+2r$
$i=\frac{3}{8+2r}$
$2=i{R}_{eq}=\frac{3}{8+2r}\times 6$
$16+4r=18$
$\Rightarrow r=0.5\Omega$