Figure shows in cross section a wall consisting of four layers with thermal conductivities `K_(1) = 0.06 W//mK, K_(3) = 0.04 W//mK` and `K_(4) = 0.10 W//mK`. The layer thickness are `L_(1) = 1.5 cm, L_(3) = 2.8 cm` and `L_(4) = 3.5 cm`. The temperature of interfaces is as shown in figure. Energy transfer through the wall is steady.

The temperature of the interface between layers `3` and `4` is:

Options

A. `2 xx 10^(-2)`
B. `2 xx 10^(-3)`
C. `4 xx 10^(-2)`
D. `4 xx 10^(-3)`

Answer

A

Explanation

`(DeltaQ)/(DeltaT):|_(layer1)`=`(DeltaQ)/(Deltat):|_(layer2)`
`rArr (0.06 xx A xx 5)/(1.5 xx 10^(-2)) = (K_(2) xx A xx 14)/(1.4 xx 10^(-2)) rArr K_(2) = 0.02 W//mK`