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An aluminium rod and a copper rod, each 1.0 m long with cross-sectional area 1 cm², are joined end to end in series. The free aluminium end is at 20 deg C and the free copper end is at 60 deg C. In steady state, find the heat conducted per second out of the hot end. (Thermal conductivity: aluminium = 200 W/(mdeg C), copper = 390 W/(mdeg C).)

1.18 J
2.36 J
3.54 J
4.72 J

Correct answer: 2.36 J

Solution

Using series thermal resistance, the heat current is about 2.36 W, i.e. 2.36 J per second.

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