The tungsten filamet of an electric lamp, has a length of 0.25 m and a diameter of `6xx10^(-5)` m. The power rating of the filament is 0.8, estimate the steady temperature of filament. Stefan's constant `=5.67xx10^(-8) W//m^(-2)//K^(4)`.

Answer

`[2615 K]`

Explanation

Here, `l=0.25 m , D= 6xx10^(-5) m`,
`P=100 W, epsilon=0.8 , T= ? , A=pi D l`
`(P)/(A)= epsilon sigma T^(4)` or `T=[(P)/(A epsilon sigma)]^(1//4) = [(P)/(pi D l epsilon sigma)]^(1//4)`
`:. T=[(100)/(3.142xx(6xx10^(-5))xx0.25xx0.8xx(5.67xx10^(-8)))]^(1//4) =2615 K`