MEPX
Chapter 5 of 10All chapters
  1. 1Heat and temperature
  2. 2The first law
  3. 3The second law
  4. 4Engines and efficiency
  5. 5How heat moves
  6. 6Gases
  7. 7Phase changes
  8. 8Thermodynamics in the world
  9. 9The statistical view
  10. 10Time and the universe

Chapter 5 of 10

How heat moves

Three mechanisms.

The three

Conduction passes energy through contact. Convection carries it in a moving fluid. Radiation sends it as electromagnetic waves and needs no medium at all.

  • Metals conduct well because free electrons carry energy quickly.
  • A vacuum flask defeats all three: vacuum, silvering and a sealed lid.

Insulation

Insulators work by trapping air so convection cannot start and conduction is slow. That is why fibrous and foamed materials work and dense ones usually do not.