Question

Two electric bulbs have filaments of lengths `L` and `2L` diameters `2d` and d and emissivities `3e` and 4e If their temperatures are in the ratio 2:3 their powers will be in the ratio of .
A. `8:27`
B. `4:27`
C. `8:3`
D. `4:9`

Answer 1

Correct Answer - B
`P =e sigma(4piR^(2))T^(4)rArr`
`(P_(1))/(P_(2))=(e_(1))/(e_(2))xx(r_(1))/(r_(2))xx(l_(1))/(l_(2))xx((T_(1))/(T_(2)))^(4)` .