a) Define the coefficient of thermal conductivity, k. What are the SI units and
ID: 2295405 • Letter: A
Question
a) Define the coefficient of thermal conductivity, k. What are the SI units and the dimensions of k?
b) Sketch how you expect the thermal conductivity of silica/quartz (SiO2) to vary with temperature over a broad range of temperature when it is (i) fused quartz glass, (ii) polycrystalline quartz and (iii) glass fiber insulation wool. Carefully but briefly explain the differences between the behaviors.
c) The thermal conductivity of copper and tin at room temperature are 400 and 70 (SI units) respectively. Which of the following do you expect to be nearest the conductivity of bronze (a 90wt% Cu, 10wt% Sn alloy): 53, 367, or 560 (SI units). Justify your choice including reasons for not choosing the other two. If copper and tin powders are mixed in the ratio 9:1 by weight and then pressed to form a block with negligible porosity, which value of conductivity would you choose then, again justifying your answer?
Explanation / Answer
a)
Coefficient of thermal conductivity of the material of a solid is equal to the rate of flow of heat per unit area per unit temperature gradient across the solid.
Its unit is W m-1 K-1.
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