Question

Determination of radiation constant of brass , iron

Answer 1

1 Determination of Radiation Constant of Iron Cylinder Aim: To determine the radiation ... Aim: To determine the radiation constant of Brass cylinder Requirements: Brass cylinder,  ...

Answer 2

"Suppose a metallic cylinder is freely suspended, the body loses energy in the form of heat by conduction, convection and radiation. Here convection is negligible and conduction is very minimum amount and hence the heat loss by radiation is higher.

Stefan-Boltzmann law provides an equation for the loss of heat energy by radiation as,

                                                              $q = bAT^4$

                q= energy radiated per sec

                b=Boltzmann constant

                A=area of radiating surface

                T=Temperature of the radiating surface

The radiation constant (α) is the product between Stefan-Boltzmann constant (σ) and the emissivity constant (ε) of a material.

For Brass,

Stefan-Boltzmann constant σ $= 5.6703 x 10^{-8} watt/m^2K^4$

Emissivity coefficient of the brass (ε) = 0.03 (at 243 ˚C)

Radiation constant = $5.6703 x 10-8 Watt/m^2K^4 x 0.03 = 0.170 x 10^{-8} (W/m^2K^4)$ (approximately)

For iron,

Stefan-Boltzmann constant σ $= 5.6703 x 10^{-8} watt/m^2K^4$

Emissivity coefficient of the iron (ε) = 0.74 (at 100˚C)

Radiation constant = $5.6703 x 10^{-8} Watt/m^2K^4 x 0.74 = 4.1960 x 10-8 (W/m^2K^4)$ (approximately)"