Question

A body at a temperature of `727^(@)C` and having surface area `5 cm^(2)`, radiations `300 J` of energy each minute. The emissivity is(Given Boltzmann constant `=5.67xx10^(-8) Wm^(-2)K^(-4)`
A. `e=0.18`
B. `e=0.05`
C. `e=0.2`
D. `e=0.15`

Answer 1

(a) `Q=Eat=esigma(T^(4)-T_(0)^(4))At`
Where `t=` time
`T_(0)=` temperature of surrounding when `TgtT_(0)`
`Q=e sigmaT^(4)At`
`300=exx(5.67xx10^(-8))(1000)^(4)(5.00xx10^(-4))(60)`
`e=0.18`