Question

Four identical bulbs each rated $100\text{watt}$ , $220\text{volts}$ are connected across a battery as shown. The total electric power consumed by the bulbs (in $\text{watt}$) is:

Answer 1

Resistance of each bulb: $R=\frac{V^2}{P}=\frac{{220}^2}{100}={22}^2\Omega$
$\therefore R_{\text{eq}}=R+\frac{R}{3}=\frac{4R}{3}$
$\therefore P=\frac{V^2}{R_{eq}}=\frac{{220}^2}{\left(4/3\right){.22}^2}$
$P=75\text{watt}$