Question

A doubled layered wall has layer A, 10 cm thick and B, 20 cm thick. The thermal conductivity of A is thrice that of B. In the steady state, the temperature difference across the wall is $ 35{{\,}^{o}}C. $ The temperature difference across the layer A is

• A. $ 28{{\,}^{o}}C $
• B. $ 14{{\,}^{o}}C $
• C. $ 7{{\,}^{o}}C $
• D. $ 5{{\,}^{o}}C $

Answer 1

Answer: (D)

In the steady state, rate of heat across each layer of the wall is the same
$ \frac{{{K}_{A}}A(\Delta T)}{10}=\frac{{{K}_{B}}A(35-\Delta T)}{20} $
using $ {{K}_{A}}=3{{K}_{B}} $
we get $ \Delta T=5{{\,}^{o}}C $