Question

If there are two bulbs of rating 100W and 60W ,then which has more resistance. Explain.

Answer 1

Let us consider the voltage be 220V for both 100W and 60W bulb

1) P1=100 W
V1 = 220 V
________________
P = V×I
P = V × (V/R)
P = V^2/R
________________
100 = (220×220)/R1
R1 = 484 ohm
________________
(2) P2 = 60 W
V2= 220 V
________________
60 = (220×220)/R2
R2 = 806.6 ohm
_______________
Hence R2 is greater than R1