Q. Two electric bulbs marked $25W - 220V$ and $100W - 220\, V$ are connected in series to a $440\, V$ supply. Which of the bulbs will fuse ?
AIEEEAIEEE 2012Current Electricity
Solution:
As $R_{1}=\frac{220}{25}\times220 $ and $R_{2}=\frac{220}{100}\times220$
$R=R_{1}+R_{2}$
$=220\times220\left(\frac{1}{25}+\frac{1}{100}\right)$
$220\times220 \frac{1}{20}$
$\therefore I_{live}=\frac{440}{\frac{220\times 220}{20}}=\frac{40}{220}A$
$\therefore $ 1st bulb (25 W) will fuse only
