Heat transfer

P1a 1.1 for AQA'S GCSE physics

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Thermal radiation + Surfaces and radiation

  • Thermal radiation is energy transfer by electromagnetical waves.
  • All objects emit thermal radiaton.
  • The hotter/more energy an object is the more energy it emits.
  • Dark matt surfaces are better emitters of thermal radiation than light shiny surfaces.
  • Dark matt surfaces are better absorbers of thermal radiation than light shiny surfaces.
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Conduction and Convection

  • Conduction in a metal is due to mainly to free electrons inside the metal.
  • Non-metals are generally poor conductors as they do not contain free electrons.
  • Materials such as fiberglass are good insulators because they contain pockets of trapped air.
  • Convection takes place only in fluids (liquids and gases)
  • Heating a fluid makes it less dense.
  • Convection is due to a hot liquid or gas rising.
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Heat transfer by design

  • Small objects lose heat more easilly than large objects.
  • Heat loss from a building can be reduced by using: aluminum foil behind radiators, cavity wall insulating, double/ triple glazing, loft insulation and under floor insulation.
  • Example: radiators have a large surface area to disperse its heat quickly.
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