Question

Two lamps, one rated 220 V, 50 W and the other rated 220 V, 100 W, are connected in series with mains of 220 V. Explain why does the 50 W lamp consume more power.

Answer 1

Resistance of 220 V , 50 W lamp is

`"R"_1 = "V"^2/"P"_1 = 220^2/50 = 968  Omega`

Resistance of 220 V , 100 W lamp is

`"R"_2 = "V"^2/"P"_2 = 220^2/100 = 484  Omega`

since the two lamps are connected in series

so same current I passes through each lamp.

Power consumed in 220 V , 50 W lamp is P₁ = I²R₁

Power consumed in 220 V , 100 W lamp is P₂ = I²R₂

Since `"R"_1 > "R"_2 , "P"_1 > "P"_2`.

i.e. 50 W lamp consumes more power.