Question

An aluminum cylinder with radius 1.7cm and length 18cm is heated to 430?C. Find the net power this cylinder radiates into a room at 23?C.

Answer 1

Radius r = 1.7 cm = 0.017 m

Area of cross section =

                                  = 9.079 x 10 ^-4 m ²

Total surface area A = 2 + 2

                             = 18.158 x 10 ^-4 + 0.019226

                             = 0.021 m ²

Length L = 18 cm = 0.18 m

If the emissivity of aluminium e = 1

Then the net power radiates P =

Where T = 430 ^o C = 430 + 273 = 703 K

         T ' = 23 ^o C = 23 + 273 = 296 K

         = Stefan constant = 5.670 x 10^-8 W m^-2 K^-4

Substitute values you get   P = 282.24 watt