A wall has two layers A and B, each made of different material. Both the layers have the same thickness. The thermal conductivity of the material of A is twice that of B . Under thermal equilibrium, the temperature difference across the wall is `36^@C.` The temperature difference across the layer A is

Options

A. `6^(@)C`
B. `12^(@)C`
C. `18^(@)C`
D. `24^(@)C`

Answer

B

Explanation

`K_(A)=2K_(B)=2K`
Heat current through both layers will be same
`((36-T)/(d))K_(A)A=((T-0)/(d))K_(B)A`
`(36-T)2K=TK`
`T=72/(3)=24`
`DeltaT` = temp difference = 36 - 24 = 12