A black body with an initial temperature of 300^(@)C is allowed to cool inside an evacuated enclosure surrounded by melting ice at the rate of 0.35^(@)C per second. If the mass, specific heat and surface area of the bodyare 32gm, 420 J kg^(-1)K^(-1) and 8 cm^(2) respectively, calculate the stefan's constant.

A black body with an initial temperature of 300^(@)C is allowed to coo

1.	A black body with an initial temperature of 300^(@)C is allowed to cool inside an evacuated enclosure surrounded by melting ice at the rate of 0.35^(@)C per second. If the mass, specific heat and surface area of the bodyare 32gm, 420 J kg^(-1)K^(-1) and 8 cm^(2) respectively, calculate the stefan's constant.
Answer» Solution :`sigmaA(T^(4)-T_(0)^(4))=mc (dT)/(dt)` `A=8xx10^(-4)m^(2), T=300+273=573K, T_(0)=0^(@)C=273K` `m=32xx10^(-3)KG, c=420Jkg^(-1)K^(-1),(dT)/dt=0.35^(@)C//sec` `sigma= (mc)/(A(T^(4)-T_(0)^(4)))XX(dT)/dt` =`(32xx10^(-3)xx420xx0.35)/(8xx10^(-4)xx(573^(4)-273^(4)))` = `5.76xx10^(-8)Wm^(-2)K^(-4)`