The graph shown gives the temperature along an `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 `150^(@)C` and on the other side is `80^(@)C`. Thermal conduction through the wall is steady. Out of the three layers `A` `B` and `C`, thermal conductivity is greatest of the layer

Options

A. `A`
B. `B`
C. `C`
D. Thermal conductivity of A = Thermal conductivity of B

Answer

A

Explanation

Rate of heat transfer is same through all walls
`(K_(1)*A*(10))/(40 cm) = (K_(2)A(20))/(20cm) = (K_(2)A(40))/(10 cm)`
`rArr (K_1)/(4) = K_(2)=4K_(3) rArr K_(1) = 4K_(2) = 16K_(3)`.