The temperature of the two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity K and\[2K\]and thickness\[x\]and\[4x,\]respectively are\[{{T}_{2}},\]and\[{{T}_{1}}({{T}_{2}}>{{T}_{1}})\]. The rate of heat transfer through the slab, in a steady state is\[\left( \frac{A({{T}_{2}}-{{T}_{1}})K}{x} \right)f,\]with f equals [AIEEE 2004] |
A) 1
B) 1/2
C) 2/3
D) 1/3
Correct Answer: D
Solution :
[d] Let the temperature of common interface be Rate of heat flow |
And |
In steady state, the rate of heat flow should be same in whole system i.e., |
Hence, heat flow from composite slab is |
.(i) |
[from Eq. (i)] |
Accordingly, |
(iii) |
By comparing Eqs. (ii) and (iii), we get |
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