A wall has two layers A and B, each made od=f different material. Both the layers have the same thickness. The thermal conductivity for A is twice that B and, under steady condition, the temperature difference across the wall is `36^(@)`C. The temperature difference across the layer A is

Explanation

For layer P, `A=A_(1),l=l_(1),K=K_(1)`
for layer Q, `A=A_(2),l=l_(2),K=K_(2)`
Given `l_(1)=l_(2),A_(1)=A_(2),K_(1)=2K_(2)`
We know
`Q/t=KA(Deltatheta)/lrArrDeltathetaalpha1/K" "(because"here "Q/t,A&l" are same")`
i.e., `(Deltatheta_(P))/(Deltatheta_(Q))=K_(Q)/K_(P)=1/2" "thereforeDeltatheta_(P)=1/3xxDeltatheta=1/3xx36=12^(@)C`