4.6 describe how energy transfer may take place by conduction, convection and radiation

Conduction

  • Conduction: Transfer of heat energy through a substance without itself moving
  • It is when atoms vibrate and heat is transferred from one atom to another
  • It is when electrons move from hot –> cold
  • Metals are good conductors of heat because this movement is faster, as the electrons are free to move
  • An increase in temperature = Increase in the average amount of movement/energy vibration

Convection

  • Convection: The transfer of heat energy through fluids (liquids and gasses) by the upward movement of warmer, less dense regions of fluid
  • When a gas or liquid is heated, it expands. As most fluids are poor thermal conductors, it happens to the closest source of heat
  • PROCESS OF EXPANSION: Density of the fluid reduces and floats upwards (Warmer fluid). Pushed out of the way by colder, denser fluid.
  • Cold water is more dense than hot water. 

Radiation

  • Radiation: Transfer of heat energy in the form of infrared waves
  • Radiation is the only method of heat transfer through a vacuum
  • Energy is transferred by electromagnetic, infrared waves at the speed of light
  • Dull, dark surfaces absorb the infrared radiation faster and are better emitters of radiation (They cool down faster)
  • Shiny, bright surfaces reflect radiation and absorb much less of it (much slower to cool down)

 

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