Question

When a (60W,20V) bulb and a (100W,220V) bulb are connected in series, when which bulb will glow brighter?

Answer 1

P=V^2/R

R = V^2 /P

Here V= 220V

Given bulbs are of 100w and 60w and are connected in series. So current for both is same.

R1 = 220*220/100= 484 ohm

R2= 220*220/60= 806.66 ohm

R2 is greater than R1.

Here power dissipation,

P= i^2 R

As current is same for both the bulbs power dissipation will be more for that bulb which has more resistance.

So, 60w bulb will glow brighter.