What will happen when a 40 watt 220 volt lamp and 100 watt-220 volt lamp are connected in series across 40 volt supply?

Options

A. 100 watt lamp will fuse
B. 40 watt lamp will fuse
C. Both lamps will fuse
D. Neither lamp will fuse

Answer

D

Explanation

(d) Bulb `(I)`: Rated current `I_(1) = (P)/(V) = (40)/(220) = (2)/(11) amp`
Resistance `R_(1) = (V^(2))/(P) = ((220)^(2))/(40) = 1210 Omega`
Bulb `(II)`: Rated current `I_(2) = (100)/(200) = (5)/(11) amp`
Resistance `R_(2) = ((220)^(2))/(100) = 484 Omega`
When both are connected in series across `40 V` supply
Total current through supply
`I = (40)/(P_(1) + P_(2)) = (40)/(1210 + 484) = (40)/(1254) = 0.03 A`
This current is less than the rated current of each bulb So neither bulb will fuse.