An electric heater is placed inside a room of total wall area 137 m 2 and maintained at a temperature 20 ° C inside, outside temperature – 10 ° C . The walls are made up of three composite materials. The innermost layer is made up of wood of thickness 2 . 5 cm , the middle layer is of cement of thickness 1 cm and the exterior layer is 25 cm thick. Assuming there is no loss of heat through any other way, the power of

Step-by-step solution

(R Th ) w = l k A = 2.5 × 1 0 - 2 0.125 × 137 = 0.2 137   ° C   W - 1 (R Th ) C = l k A = 1 × 1 0 - 2 1.5 × 137 = 0.0067 137   ° C   W - 1 (R Th ) B = l k A = 25 × 1 0 - 2 1 × 137 = 0.25 137   ° C   W - 1 R Th = (R Th ) w +(R Th ) C + (R Th ) B = 0.2 + 0.0067 + 0.25 137 =   3 . 33 × 10 - 3 ° C   W - 1 Rate of heat flow = θ 1 - θ 2 R T h = 20 - - 10 3.33 × 1 0 - 3 =   9000   W