Question

A cubical block of mass `1.0kg` and edge `5.0cm` is heated to `227^(@)C` . It is kept in an evacuated chamber maintained at `27^(@)C` . Assming that the block emits radiation like a blackbody, find the rate at which the temperature of the block will decreases. Specific heat capacity of the material of the block is `400Jkg^(-1)K^(-1)` .

Answer 1

`(dT)/(dt) = (e sigma A)/(ms) (T^(4) - T_(0)^(4))`
`sigma = 1, A = 6 a^(2) = 6xx (5 xx 10^(-2))^(2) = 150 xx 10^(-4) m^(2)`
`T = 227 + 273 = 500 K, T_(0) = 27 + 273 = 300 K`
`m = 1 kg, s = 400 J//kg-K`
`= 2.25 xx 10^(-12) xx (625 xx 81) xx 10^(8)`
`= 0.12^(@)C//s`