Practice Heat Transfer in Physics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

The spontaneous flow of thermal energy from a hotter object to a cooler one until they reach the same temperature.

Heat always flows from hot to cold on its own — reversing this requires external work.

Example 1

easy
Identify the primary mode of heat transfer in each case: (a) a metal spoon in hot soup, (b) warmth from a campfire, (c) a pot of water being heated on a stove.

Example 2

medium
A glass window (k = 0.8 \text{ W/(m·K)}, area 2 \text{ m}^2, thickness 0.005 \text{ m}) has 20°\text{C} inside and 5°\text{C} outside. What is the rate of heat loss through the window?

Example 3

medium
A thermos flask uses a vacuum between its double walls. Explain why this reduces heat transfer, and which mode(s) of heat transfer it primarily blocks.

Example 4

hard
A copper rod (k = 385 \text{ W/(m·K)}) and an iron rod (k = 80 \text{ W/(m·K)}) have the same length (0.5 \text{ m}) and cross-sectional area (0.001 \text{ m}^2). Both connect a 100°\text{C} source to a 25°\text{C} sink. What is the rate of heat conduction through each?
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