Heat Transfer Examples in Physics

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Heat Transfer.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.

Concept Recap

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

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

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Heat is energy in transit between objects — it flows, it is not stored in an object.

Common stuck point: Objects don't 'have' heat—they have thermal energy. Heat is the transfer.

Sense of Study hint: When solving a heat transfer problem, first identify which mechanism is involved (conduction, convection, or radiation). Then determine the temperature difference, as heat always flows from higher to lower temperature. Finally, use the appropriate formula: Q = mc\Delta T for the amount of heat causing a temperature change, or specific formulas for each mechanism.

Worked Examples

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.

Solution

  1. 1
    (a) The metal spoon heats up by conduction — direct contact transfers energy through molecular collisions.
  2. 2
    (b) The campfire warmth reaches you by radiation — infrared electromagnetic waves carry energy through air.
  3. 3
    (c) The water circulates by convection — hot water rises and cool water sinks, creating circulation currents.

Answer

\text{(a) Conduction, (b) Radiation, (c) Convection}
Heat transfers through three mechanisms: conduction (direct contact), convection (fluid circulation), and radiation (electromagnetic waves). Most real situations involve a combination of all three.

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?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

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 2

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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Background Knowledge

These ideas may be useful before you work through the harder examples.

thermal energy