Question

Two electric bulbs have 60 W and 100 W rating at 220 V then ratio of their resistances will be​

Answer 1

Explanation:

using P=VI formula

I ( current of 1st electric bulb ) = P/V

So, I=60/220=3/11A ..... (1)

then now , let

í ( current of 2nd bulb )=P/V

so, í=100/220=5/11 A ..... (2)

now using (1) and (2) and V=IR formula ( ohm's law )

R ( resistance of 1st bulb ) /

R' ( resistance of second bulb ) = V/I / V/Í= Í/I

= 5/11/3/11

= 5/3

Hence required ratio is 5:3

Answer 2

Answer:

3 : 2

Explanation:

P = V2 /R → P is proportional to 1/R

P1/P2 = R2/R1 → R1/R2 = P2/P1

R1/R2 = 60/40 = 3 : 2