A copper rod and an aluminium rod, each 0.80 m long with a cross-section of 1.5 cm², lie side by…

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A copper rod and an aluminium rod, each $0.80\ \text{m}$ long with a cross-section of $1.5\ \text{cm}^2$ , lie side by side, lagged, with one end of each at $100\ ^\circ\text{C}$ and the other at $0\ ^\circ\text{C}$ . Find the total heat flow, and how much goes through the copper. ( $k$ : copper $385\ \text{W m}^{-1}\text{K}^{-1}$ , aluminium $205\ \text{W m}^{-1}\text{K}^{-1}$ .)

Need a reminder? The key ideaShow

Conduction: $H = \dfrac{kA\,\Delta T}{L}$ ; thermal resistance $\dfrac{L}{kA}$ , adding for layers in series. $k$ : copper $385\ \text{W m}^{-1}\text{K}^{-1}$ , aluminium $205\ \text{W m}^{-1}\text{K}^{-1}$ , steel $50\ \text{W m}^{-1}\text{K}^{-1}$ , glass $0.8\ \text{W m}^{-1}\text{K}^{-1}$ .

The worked solution

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