Question

The graph shown given the temperature along x axis that extends directly through a wall consisting of three layers A,B and C.The air temperature on one side of the wall is ${15}^{o}C$ and on the other side is ${80}^{o}C$. Thermal conduction through the wall is steady. Out of the three layers A,B and C thermal conductivity is greatest of the layer:

• A. A
• B. B
• C. C
• D. Insufficient information to decided

Answer 1

The correct option is A A

At steady state rate of heat transfer is equal for all wall Therefore, we can write,

$\frac{K_A\times A\times (150-140)}{(40-0)}=\frac{K_B\times A\times (140-120)}{(60-40)}=\frac{K_C\times A\times (120-80)}{(70-60)}$

$\frac{K_A\times 10}{40}=\frac{K_B\times 20}{20}=\frac{K_C\times 40}{10}$

$\frac{K_A}{4}=K_B=4K_C$

$K_A=4K_B=16K_C$

Hence, Thermal conductivity is greater than B and C is A.

option (A) is correct option.