A hollow tube has a length `l`, inner radius `R_(1)` and outer radius `R_(2)` . The material has a thermal conductivity `K`. Find the heat flowing through the walls of the tube if
(a) the flat ends are maintained at temperature `T_(1)` and `T_(2)``(T_(2)gtT_(1))`
(b) the inside of the tube is maintained at temperature `T_(1)` and the outside is maintained at `T_(2)` .

Answer

`(Kpi(R_(2)^(2)-R_(1)^(2))(T_(2)-T_(1)))/(I)`

Explanation

`(dQ)/(dt) = KA ((T_(2)-T_(1))/(l))`
Here `A = pi (R_(2)^(2) -R_(1)^(2))`