A wall has two layers A and B each made of different materials. The thickness of both the layers is the same. The thermal conductivity of A, `K_(A) = 3K_(B)`. The temperature different across the wall is `20^(@)C` in thermal equilibrium

Options

A. The temperature difference across A=`15^@`C
B. The temperature difference across A=`5^@`C
C. The temperature difference across A is `10^@`C
D. The rate of transfer of heat through A is more than that through B

Answer

B

Explanation

Rate of flow of heat is same

`implies (K_A A(T_1-T))/(l)=(K_B A(T-T_2))/(l)`
`implies 3K_B(T_1 - T)=K_B(T-T_2)`
`3T_1-3T=(T-T_2)`
`4T_1-4T=T_1-T_2`
`4(T_1-T)=20 implies T_1 - T =5^@C`