Question

Two bulbs of equal wattage, one having carbon filament and the other having a tungsten filament, are connected in series to the mains. Then

• A. carbon filament bulb glows less.
• B. carbon filament bulb glows more.
• C. both bulbs glow equally.
• D. tungsten filament bulb glows more.

Answer 1

The correct option is B carbon filament bulb glows more.

Here, carbon filament bulb and the tungsten filament bulb, are connected in series, hence current through them is same. Therefore,
$Q=I^{2}Rt$
$\Rightarrow Q\propto R$
Also, carbon is non-metal (semiconductor) and tungsten is metal (conductor) hence, the resistance of carbon filament is more than tungsten filament. Hence, carbon filament bulb glows more than tungsten filament bulb.