Q

# A house is served by 220 V supply line in a circuit protected by a 9 ampere fuse

A house is served by 220 V supply line in a circuit protected by a 9 ampere fuse. The maximum number of 60 W lamps in parallel that can be turned on, is A) 44 B) 20 C) 22 D) 33
$power = \frac{V^2}{R} , so R_{bulb}= \frac{220^2}{60}=806.66\ ohm \\Resistance of circuit = \frac{V}{I} = \frac{220}{9} = 24.44\ ohm\\ let\ n\ bulbs\ are\ in\ parallel, then\ net\ resistance\ is \frac{n}{R_{bulb}}\\so\frac{1}{R}=\frac{n}{R_{bulb}}\\\therefore n=\frac{806.66}{24.44}=33\ bulbs$