Question

A wall has two layers A and B. each made of different material. Both the layers have the same thickness. The thermal conductivity for A is twice that of B. Under steady state, the temperature difference across the whole wall is ${36}^{0}C$ .Then the temperature difference across the layer A is.

• A. $6^{0}C$
• B. ${12}^{0}C$
• C. ${18}^{0}C$
• D. ${24}^{0}C$

Answer 1

The correct option is B ${12}^{0}C$

In thermal equilibrium the rateo f flow across the two layers is same.

$\frac{2k\left(\Delta T_1\right)A}{L}=\frac{k\left(\Delta T_2\right)A}{L}\Rightarrow \frac{\Delta T_1}{\Delta T_2}=\frac{1}{2}\Rightarrow \frac{\Delta T}{36-\Delta T_1}=\frac{1}{2}\Delta T_1=12°C$

Temperature difference across layer A is $12°C$