A exterior wall must be insulated so that the conductive energy loss does not exceed…

PHYSICS · Subjective · CBSE · Physics · Thermal Properties of Matter · Thermal Properties of Matter

Problem

15\,\text{m}^2

exterior wall must be insulated so that the conductive energy loss does not exceed

500\,\text{W}

when the indoor-outdoor temperature difference is

30\,\text{K}

. Two candidate insulation materials are available:

Material	Thermal conductivity	Cost
A	$0.035\,\text{W m}^{-1}\text{K}^{-1}$	$45$ dollars per $\text{m}^3$
B	$0.020\,\text{W m}^{-1}\text{K}^{-1}$	$70$ dollars per $\text{m}^3$

Assuming the entire wall is uniformly filled with one material, which material meets the heat-loss requirement at the lower total cost? State the material letter only.

Related theory

Heat Transfer
Thermal conduction
Heat transfer by conduction
Thermal Properties of Matter

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