Question

Two equal resistance, when connected in series to a battery, consume electric power of $60\text{W}$. If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be:

• A. $60\text{W}$
• B. $240\text{W}$
• C. $120\text{W}$
• D. $30\text{W}$

Answer 1

The correct option is B $240\text{W}$

When two equal resistance are connected in series,
$R_{eq}=2R$

$\text{Power consumed,}P=\frac{V^2}{R_{eq}}=\frac{V^2}{2R}$

$\text{In parallel condition,}{R}_{eq}=\frac{R}{2}.$

$\text{New power,}{P}^{\prime }=\frac{V^2}{\left(\frac{R}{2}\right)}$

$\Rightarrow P^{\prime }=4P=240\text{W}$

Hence, option $\left(B\right)$ is correct.