Two rods connect a heat reservoir that holds 0◦ C with a heat reservoir that
holds 100 ◦ C. Both rods are 1.0 m long and have a square cross-section with side-
edges 5.0 cm. We assume that the rods have been in contact with both reservoirs above
long time, and that the rods are well insulated so that the heat flow through the rods in
its entirety goes from the hot reservoir to the cold – that is, no leakage to the rest
surroundings.
The upper rod consists of 40 cm of copper connected together with 60 cm of steel.
The lower rod consists of 20 cm of copper at each end with 60 cm of steel in the middle. Heat-
the lead coefficients for steel and copper are k steel = 50,2 W/(m·K) and
k Cu = 385 W / (m · K).
(a) Is there a difference in the heat flow through the two rods? Which is eventuelt largest? Justify the answer.
(b) Sketch the temperature in each of the two rods as a function of distance from
the end which is in contact with the cold reservoir. Calculate the temperature in
the point where copper and steel meet in the upper rod.
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