Question

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

• A. $75$ watt
• B. $400$ watt
• C. $300$ watt
• D. $400/3$ watt

Answer 1

The correct option is A $75$ watt

From figure we see the combination of bulb in series and parallel,so replaced all the bulb with unknown resistance "R"
Power(P)=$\frac{v^2}{R}$
so,Resistance{R}=$\frac{v^2}{P}$=$\frac{{220}^2}{100}$=484$\Omega$.
on solving the equivalent resistance of the circuit we find $R_{equivalent}$=645.33$\Omega$.
therefore total power across the circuit will be(P)=$\frac{v^2}{R}$=$\frac{{220}^2}{645.33}$=75watt