Question

Energy is emitted from a hole in an electric furnace at the rate of 20 watt when the furnace is at ${227}^{0}C$. Find the area of the hole. [$\sigma =5.7\times {10}^{-8}$ S. I. units. ]

Answer 1

Given : $P=20W$ $T={227}^{o}C=500K$

Using $P=\sigma Ae{T}^4$

Or $20=5.67\times {10}^{-8}\times A\times 1\times (500{)}^4$

$⟹A=0.0056m^2$