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An aluminium rod is joined end-to-end with a copper rod. Each rod is 20 cm long with cross-section 0.20 cm². The junction is held at 40 C and both outer ends are kept at 80 C. After steady state, how much heat is removed from the cold junction in one minute? (K_Al = 200 W/m-C, K_Cu = 400 W/m-C)

1. 144 J
2. 192 J
3. 240 J
4. 288 J

Correct answer: 288 J

Solution

Heat flows from both 80 C ends to the 40 C junction; summing the two rod contributions over 60 s gives 288 J.

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