Question

Determine the net heat radiated by the black body disc of mass 6g and radius 4cm at 40⁰C, initially kept at 30⁰C.

Answer 1

Solution;

By Stefan-Boltzmann's law of radiation,the net rate of heat transfer by radiation is;

$\frac {Q_{net}}{t}=\sigma Ae(T_2^4-T_1^4)$

For a black body,e=1

$A=πr^2=π×0.04^2=$5.026×10^-3m²

$\frac{Q_{net}}{t}=5.67×10^{-8}×5.026×10^{-3}×(313^4-303^4)$

$\frac{Q_{net}}{t}=0.33331J/s$