Question

A spherical ball of surface area $20m^2$ absorbs any radiation that falls on it. it is suspended in a closed box maintained at ${57}^{0}C$ (a) Find the net rate of heat flow to or from the ball at an instant when its temperature is ${200}^{0}C$ stefan constant = $6.0\times {10}^{-8}W{m}^{-3}{K}^{-4}$

Answer 1

Given,

$A=20c{m}^2=20\times {10}^{-4}{m}^2$

$T=57°C=57+273=330K$

(a)

$\to E=A\sigma T^4$

$\to E=20\times {10}^{-4}\times 6\times {10}^{-8}\times (330{)}^4$

E = 1.42 J