Question

A thin brass rectangular sheet of sides 15.0 and 12.0 cm is heated in a furnace to `600^@` C and taken out. How much electric power is needed to maintain the sheet at this temperature, given that its emissivity is 0.250?
Neglect heat loss due to convection (Stefan-Boltzmann constant, `sigma=5.67xx10^-8 W//m^(2)-K^(4)`).

Answer 1

Area of both sides of the plate
`A=2xx(15.0)xx(12.0)xx10^-4m^2=3.60xx10^-2m^2`
The energy radiated by the plate
`=esigmaAT^4=0.250xx5.67xx10^-8xx3.60xx10^-2xx(600+273)^4`
`=5.10xx10^(-12)xx873^4=296.4W`