A composite flat wall of a furnace is made of two materials ‘A’ and ‘B’. The thermal conductivity of ‘A’ is twice of that of material ‘B’, while the thickness of layer of ‘A’ is half that of B. If the temperature at the two sides of the wall are 400 and 1200°K, then the temperature drop (in °K) across the layer of material ‘A’ is________________?
Correct answer: D
Explanation
The temperature drop across a layer is proportional to the ratio of thermal conductivity and thickness. Given the ratios, the calculated value matches 160°K.