Question

Two bulbs have the following ratings.
40 W,220 V
20W,100 V
The ratio of their resistance is?

Answer 1

Answer:

R1:R2 = 121:50

Explanation:

The calculations are attched with this answer.

Good luck!

Answer 2

Answer:

Equation of power in terms of voltage and resistance is

P = V^2/R Or

R = V^2/P

R1 = 220^2/40 = 1210 ohm

R2 = 110^2/20 = 605

R1 : R2 = 1210 : 605

R1 : R2 = 2:1

hope it helps...