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

`H=(2k(T_(1)-T))/(L)=(kA(T-T_(2)))/(L)rArr2T_(1)-3T=-T_(2)`
Adding `T_(1)` on both sides:
`3T_(1)-3T=T_(1)-T_(2)rArrT_(1)-T=(T_(1)-T_(2))/(3)=(36)/(3)=12^(@)C`