Question

Internal resistance of a $2.1V$ cell which gives a current of 0.2 A through an external resistance of $10\Omega$ is

• A. $0.2\Omega$
• B. $0.5\Omega$
• C. $0.8\Omega$
• D. $1.0\Omega$

Answer 1

The correct option is B $0.5\Omega$


$\frac{2.1}{10+r}=0.2$
$2.1=2+0.2r$
$0.1=0.2r$
$⟹r=0.5\Omega$