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 in steady state. the temperature of the interface between layer `3 and 4` is:

Options

A. `-1^(@)C`
B. `-3^(@)C`
C. `2^(@)C`
D. `0^(@)C`

Explanation

in steady state `(triangleQ)/(trianglet)|_("layer 1")` = `(triangleQ)/(trianglet)|_("layer 4")`
`=(0.06xxAxx(30-25))/(1.5xx10^(-2))=(0.10xxAxxtriangleT)/(3.5xx10^(-2))impliesDT=7^(@)C`
`T_(3)=(-10+7)^(@)C=-3^(@)C`