Question

A wall has two layers A and B made of different materials. The thickness of both the layers is the same. The thermal conductivity of A and B are KA and KB such that KA=3KB. The temperature acros the wall is 20 degree celsius . In thermal equilibrium is?


(a) The temperature difference across A=15degree celsius

(b) The temperature difference across A=5 degree celsius

(c) The temperature difference across A is 10 degree celsius

(d) The rate of transfer of heat A is more than that through B

Answer 1

(b) The temperature difference across A=5 degree Celsius
(3K)A(T-0)/d=(K)A(20-T)/d
(3K)A(T)=(K)A(20-T)
(3)T=(20-T)
T=5 ℃