Question

If the reading of the ideal voltmeter shown in the circuit is $2V$ the internal resistance of the two identical cells is

• A. $1\Omega$
• B. $0.5\Omega$
• C. $1.5\Omega$
• D. $2\Omega$

Answer 1

Answer: (B)

$0.5\Omega$

$i=\frac{3}{8+2r}$
$\therefore$ Reading of voltmeter = $i\times 6=\frac{3}{8+2r}\times 6=2$
$\Rightarrow 2r+8=9\Rightarrow r=\frac{1}{2}\Omega$