IB Physics SL B 1 12 Conduction Rate Questions

Practise conduction-rate calculations with conductivity, area, thickness, temperature difference and graphs in exam questions.

Exam points

Apply ΔQ/Δt = kAΔT/Δx to relate conduction rate to conductivity, area, temperature gradient and thickness.
Calculate or compare conduction rates using consistent units and complete mark-scheme evidence.

[Maximum number: 3]

A cylindrical cork of height H and cross-sectional area A is floating stationary in water. Its depth below the water surface is D.

Figure for Question IB Physics SL B 1 12 Conduction Rate Questions question 1 — IB Physics SL

(a)

On a winter day, the surface of a lake is frozen. The temperature of the air above the lake is $-6.0^{\circ} \mathrm{C}$ . The layer of ice frozen on the surface of the lake has a thickness of 1.9 cm .

[ 3 ]

(i)

The thermal conductivity of ice is $2.3 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}$ . Calculate the rate per unit area at which thermal energy leaves the lake by conduction through the ice layer.

[ 2 ]

$\begin{aligned} \text { use of } \Delta \mathrm{T}=6<^{\circ} \mathrm{C} \gg \frac{\Delta Q}{\Delta t A}=\ll \frac{2.3 \cdot 6}{0.019}=\gg 730<\mathrm{W} \mathrm{~m}^{-2} \gg \end{aligned}$

(ii)

Explain how the rate per unit area at which thermal energy leaves the lake by conduction through the ice layer changes as the layer of ice grows thicker.

[ 1 ]

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IB Physics SL B 1 12 Conduction Rate Questions question 1

Question (a)

Question (i)

Question (ii)