A sphere of surface area 4 m 2 at temperature 400 K and having emissivity 0 . 5 is located in an environment of temperature 200 K . The net rate of energy exchange of the sphere is (Stefan Boltzmann constant σ = 5 . 67 × 10 - 8 W m - 2 K 4 )

Step-by-step solution

The net rate of energy exchange of the sphere is, P = ε σ A T 4 - T s 4 . Given: ε = 0 . 5 σ = 5 . 67 × 10 - 8   W   m - 2   K 4 A = 4   m 2 T = 400   K and T s = 200   K Therefore, P = 0 . 5 × 5 . 67 × 10 - 8 × 4 400 4 - 200 4 = 2721 . 6   W