Question

A metal ball of surface area $200c{m}^2$ and temperature ${527}^{0}C$ is surrounded by a vessel at ${27}^{0}C.$ If the emissivity of the metal is 0.4, then the rate of loss of heat from the ball is $\sigma =5.67\times {10}^{-8}J/m^2-s-k^4$

• A. 108 joules approx
• B. 168 joules approx
• C. 182 joules approx
• D. 192 joules approx

Answer 1

The correct option is C

182 joules approx

$RateofheatlossE=\sigma eA(T^4-T_0^4)=5.67\times {10}^{-3}\times 0.4\times 200\times {10}^{-4}\times \left[\right(273+527{)}^4-(273+27{)}^4]=5.67\times {10}^{-3}\times 0.4\times 200\times {10}^{-4}\times (800{)}^4-(300{)}^4=182J/Sec$