Two bulbs have the following ratings (i) 40W, 220V (ii) 40W, 110V. The ratio of their resistances is :
(a) 1 : 2
(b) 4 : 1
(c) 1 : 4
(d) 2 : 1
Correct option (b) 4 : 1
Explanation:Resistance of the bulb is
R = V2/P
Where P = power of the bulb
V = voltage across the bulb
R = resistance of the bulb
