Question

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

• A. 25
• B. 100
• C. Both
• D. Neither

Answer 1

The correct option is A 25

Resistances of both the bulbs are

$R1=\frac{V^2}{P_1}=\frac{{220}^2}{25}$

R2 =$\frac{V^2}{P2}=\frac{{220}^2}{100}$

hence$R_1:R_2$

When connected in series, the voltages divide in them in the ratio of their resistances. The voltage of 440 V devides in such a way that voltage across 25 w bulb will be more than 220 V. Hence 25 w bulb will fuse.