A 25 W, 220V bulb and 100W, 220V bulb are joined in series and connected to the mains. Which bulb will glow brighter-

Options

A. 25W bulb
B. 100 W bulb
C. First 25 W bulb and then 100 W bulb
D. both will glow with same brightness

Answer

A

Explanation

(Brightness )`prop` (Consumed power) ……..i
For series combination
`P_("consumed")=i^(2)R`
`:.P_("consumed")propR`………..ii
Also rated power
`P_("Rated")=(V^(2))/R`
`P_("rated")prop1/R`……….iii
(Brigthnes) `prop(1/(P_("rated")))`
`:.25W` bulb will glow birighter.