A homeowner compares two exterior walls of identical thickness and area: one…
PHYSICS · Multi-part · A Level · Physics · Further mechanics and thermal physics · Further mechanics and thermal physics
Problem
A homeowner compares two exterior walls of identical thickness and area: one constructed entirely of common brick and the other of pine wood boards. On a winter day the indoor air is maintained at 20∘C while the outdoor air remains at 0∘C. Ignore any convection or radiation losses so that conduction through each wall is the only energy transfer pathway.
(a) Describe qualitatively which wall transfers energy to the outdoors at a greater rate and cite the physical property that most directly explains the difference.
(b) Explain how doubling the thickness of either wall would affect the rate of energy transfer, and justify your reasoning without performing a numerical calculation.
(c) Suppose the brick wall is coated on the outside with a thin layer of insulation whose thermal conductivity is much smaller than that of brick. Explain how adding this layer alters the temperature gradient within the brick itself and how that change influences the overall conduction rate.