EasyPhysicsHigh School (11–12)Heat & Thermodynamics › Heat TransferNumericalBoard Exam AP IB

A pane of glass has an area of 1.2 m² and a thickness of 3.0 mm.

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A pane of glass has an area of $1.2\ \text{m}^2$ and a thickness of $3.0\ \text{mm}$ . Its inside face is $10\ \text{K}$ warmer than its outside face. How much heat flows through it each second? ( $k = 0.8\ \text{W m}^{-1}\text{K}^{-1}$ .) Why do double-glazed windows lose far less?

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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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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