The wall with a cavity consists of two layers of brick separated by a layer of air.All three layers have the same thickness and the thermal conductivity of the brick is much greater than that of air. The left layer is at a higher temperature than the right layer and steady state condition exists. Which of the following graphs predicts correctly the variation of temperature $T$ with distance $d$ inside the cavity?
A
B
C
D
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D
d Each individual section is in steady state, i.e. the temperature drops linearly with distance. (all three parts must be linear)
The lesser the conductivity, larger is the temperature drop.
Hence option $(D)$ matches
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