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

Options

A. `11^(@)C`
B. `8^(@)C`
C. `7.2^(@)C`
D. `5.4^(@)C`

Answer

A

Explanation

`(DeltaQ)/(DeltaT):|_(layer1)`=`(DeltaQ)/(Deltat):|_(layer3)`
`rArr (0.06 xx A xx 5)/(1.5 xx 10^(-2)) = (004 xx A xx DeltaT)/(2.8 xx 10^(-2))`
`rArr DeltaT = 14^(@)C , T_(3) = (-3 +14)^(@)C = 11^(@)C`