One experimental method of measuring an insulating material\'s thermal conductiv

Question

One experimental method of measuring an insulating material's thermal conductivity is to construct a box of the material and measure the power input to an electric heater inside the box that maintains the interior at a measured temperature above the outside surface. Suppose that in such an apparatus a power input of 175 W is required to keep the interior surface of the box 66.0 Celcius ( about 151 fahrenheit) above the temperature of the outer surface. The total area of the box is 2.17 meters square , and the wall thickness is 4.10 cm.Find the thermal conductivity of the material in SI units.
Express your answer using two significant figures.

Explanation / Answer

Power input into the box= heat loss by conduction out of it.

Q=kAT/l

A=surface area

l=thickness

k=conductivity

k=Ql/(AT)=175*4.1*10-2/(2.17*66)=0.05 W/m-K

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