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Chapter 14 | Heat and Heat Transfer Methods 583
14 HEAT AND HEAT TRANSFER METHODS
Figure 14.1 (a) The chilling effect of a clear breezy night is produced by the wind and by radiative heat transfer to cold outer space. (b) There was once great controversy about the Earth’s age, but it is now generally accepted to be about 4.5 billion years old. Much of the debate is centered on the Earth’s molten interior. According to our understanding of heat transfer, if the Earth is really that old, its center should have cooled off long ago. The discovery of radioactivity in rocks revealed the source of energy that keeps the Earth’s interior molten, despite heat transfer to the surface, and from there to cold outer space.
Chapter Outline
14.1. Heat
14.2. Temperature Change and Heat Capacity 14.3. Phase Change and Latent Heat
14.4. Heat Transfer Methods
14.5. Conduction
14.6. Convection
14.7. Radiation
Connection for AP® Courses
Heat is one of the most intriguing of the many ways in which energy goes from one place to another. Heat is often hidden, as it only exists when energy is in transit, and the methods of transfer are distinctly different. Energy transfer by heat touches every aspect of our lives, and helps us to understand how the universe functions. It explains the chill you feel on a clear breezy night, and why Earth’s core has yet to cool.
In this chapter, the ideas of temperature and thermal energy are used to examine and define heat, how heat is affected by the thermal properties of materials, and how the various mechanisms of heat transfer function. These topics are fundamental and practical, and will be returned to in future chapters. Big Idea 4 of the AP® Physics Curriculum Framework is supported by a discussion of how systems interact through energy transfer by heat and how this leads to changes in the energy of each system. Big Idea 5 is supported by exploration of the law of energy conservation that governs any changes in the energy of a system. Heat involves the transfer of thermal energy, or internal energy, from one system to another or to its surroundings, and so leads to a change in the internal energy of the system. This is analogous to the way work transfers mechanical energy to a mass to