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 ?

Question

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 ? (A) both (B) 100W (C) 25W (D) neither

Tardigrade Admin · Accepted Answer

As R1=(220/25)×220 and R2=(220/100)×220 R=R1+R2 =220×220((1/25)+(1/100)) 220×220 (1/20) ∴ Ilive=(440/(220× 220)20)=(40/220)A ∴ 1st bulb (25 W) will fuse only

Q. Two electric bulbs marked $25 W - 220 V$ and $100 W - 220 V$ are connected in series to a $440 V$ supply. Which of the bulbs will fuse ?

both

$100 W$

$25 W$

neither

As $R_{1} = \frac{220}{25} \times 220$ and $R_{2} = \frac{220}{100} \times 220$
$R = R_{1} + R_{2}$
$= 220 \times 220 (\frac{1}{25} + \frac{1}{100})$
$220 \times 220 \frac{1}{20}$
$∴ I_{l i v e} = \frac{440}{\frac{220 \times 220}{20}} = \frac{40}{220} A$
$∴$ 1st bulb (25 W) will fuse only

Q. Two electric bulbs marked 25W−220V and 100W−220V are connected in series to a 440V supply. Which of the bulbs will fuse ?