Question

If $E=6\text{V}$, $r=2R$ then maximum power dissipated through $R$ is

• A. $18\text{W}$
• B. $9\text{W}$
• C. $36\text{W}$
• D. $3\text{W}$

Answer 1

The correct option is B $9\text{W}$

Equivalent emf of cell,
$E_{net}=E=6\text{V}$
Equivalent or internal resistance,
$r_{eq}=\frac{r}{2}=R$
$\Rightarrow$Maximum power is dissipated when,
$r=R(=r_{eq})$
Power dissipated, $P=I^{2}R$
$\Rightarrow P={\left(\frac{6}{1+1}\right)}^2\times 1$
$\therefore P=9\text{W}$