Question

The surface of a black body is at a temperature ${727}^{o}C$ and its cross section is $1m^2$. Heat radiated from this surface in one minute in Joules is (Stefan's constant$=5.7\times {10}^{-8}W/m^2/k^2$

• A. $34.2\times {10}^5$
• B. $2.5\times {10}^5$
• C. $3.42\times {10}^5$
• D. $2.5\times {10}^6$

Answer 1

The correct option is A $34.2\times {10}^5$

Given : $T={727}^{o}C=727+273=1000K$ $\sigma =5.7\times {10}^{-8}W/m^2/K^2$ $e=1$
Area of the surface $A=1m^2$
Time $t=60s$
Heat radiated by surface $H=\sigma Ae{T}^{4}t$
$⟹H=5.7\times {10}^{-8}\times 1\times 1\times (1000{)}^4\times 60=34.2\times {10}^{5}J$