A spherical tungsten pieces of radius `1.0cm` is suspended in an evacuated chamber maintained at `300K`. The pieces is maintained at 1000K by heating it electrically. Find the rate at which the electrical energy must be supplied. The emissivity of tungsten is `0.30` and the Stefan constant `sigma` is `6.0xx10^(-s)Wm^(-2)K^(-4)` .

Answer

22

Explanation

`E = sigma eA lfloor(100)^(4) -(300)^(4)rfloor`
where `A = 4pi r^(2) & r = 0.01 m`.