Thermal Energy Transfer: Conduction, Convection, Radiation

   
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  • All things are made up of molecules
  • When things get heated, they absorb heat energy
  • With more energy, molecules are able to move faster
  • When molecules move faster, the temperature rises

What is Thermal Energy???

  • Thermal Energy is energy resulting from the motion of particles
  • It is a form of kinetic energy and is transferred as heat
  • Thermal Energy Transfer can occur by three methods:
  • Conduction
  • Convection
  • Radiation

Conduction

  • Conduction is the transfer of thermal energy through direct contact between Convection Conduction Thermal Energy Transfer: Conduction, Convection, Radiationparticles of a substance, without moving the particles to a new location
  • Usually occurs in solids
  • When heat is supplied to one end, molecules at that end start to move more quickly
  • In the process, they bump into their neighbours, transferring the kinetic energy

Convection

  • Convection is the transfer of thermal energy through movement of particles from one location to another
  • Usually occur in fluids (liquids and gases)
  • Example with boiling water:
  • Water at bottom of pan is heated first
  • Heated water expands and density decreases
  • Heated water begins to rise
  • Cooler water with higher density from the sides of the pan rush down to take its place
  • The cooler water gets heated and the cycle repeats
  • We call these Convection Currents

Radiation

  • Radiation is the emission of energy as waves or particles or rays
  • Radiation does not require a medium to transfer energy
  • Radiant energy is either reflected or absorbed by matter
  • Energy that is absorbed increases the kinetic energy of the object
  • This increases the temperature of the object
  • Example … frying pan on a stove top
  • Energy is radiated from the heat source and absorbed by the lower surface of the pan
  • Example … the sun
  • Sun radiates energy in form of solar radiation
  • When this energy reaches Earth, it is absorbed by matter (air, water, land)
  • Absorbed radiant energy increases kinetic energy of the matter, raising its temperature
  • The sun is an emitter
  • It gives out heat
  • The Earth is an absorber
  • It takes in the heat

Factors Affecting Radiation

ALBEDO

  • Colour of the surface
  • Albedo is the percentage of the incoming solar radiation that it reflects
  • Albedo of Earth is about 30%
  • Light-coloured, shiny objects reflect more solar radiation and have a high albedo (ice, snow, sand)
  • Darker, dull objects absorb more solar radiation and have a low albedo (forests, soils)
  • Factors Affecting Radiation
  • Surface Temperature
  • The higher the surface temperature, the higher the rate of transfer

ALBEDO1 Thermal Energy Transfer: Conduction, Convection, Radiation

Surface Area

  • The larger the surface area, the higher the rate of transfer
  • Thermal Energy Transfer in the Atmopshere
  • Things to Know:
    • Atmospheric Pressure > the pressure exerted by the mass of air above any point on Earth’s surface
    • Warm air is less dense than cold air
    • Warmer regions generally have less atmospheric pressure than colder regions
    • Wind > the movement of air from areas of high pressure to areas of low pressure
    • The rising and sinking masses of air in convection currents cause changes in atmospheric pressure … causing wind

Wind Patterns and Coriolis Effect:

  • Moves from WEST to EAST
  • Closer to equator in colder monthes
  • Closer to Poles in warmer months
  • Thermal Energy Transfer in the Hydrosphere
  • Effect of water on transfer of heat is significant
  • Earth’s climate is effected by phase changes in the water cycle

Water Cycle

  • Water molecules undergo changes of state (e.g. solid to liquid)
  • When these changes occur, thermal energy is either released or absorbed
  • Released from liquid > solid
  • Absorbed from Liquid > gas
  • Temp. remains the same between phase changes
  • Through changes of state is how thermal energy is transferred through the biosphere

Ocean Currents

  • Main pathways to transfer thermal energy from warmer regions to cooler regions
  • Global winds push the water, driving the surface currents of the ocean
  • Pattern of ocean currents is modified by the Coriolis Effect
  • Currents in North veer to the right
  • Currents in South veer to the left
  • Thermal energy is also transferred vertically via convection currents
  • (same principles as with air)
 

Citation


St. Rosemary Educational Institution. "Thermal Energy Transfer: Conduction, Convection, Radiation." http://schoolworkhelper.net/. St. Rosemary Educational Institution, Last Update: 2014. Web. Retrieved on: Wednesday 23rd April 2014. http://schoolworkhelper.net/thermal-energy-transfer-conduction-convection-radiation/.
6 responses to “Thermal Energy Transfer: Conduction, Convection, Radiation”
  1. Halil says:

    thanks so much! I’ve got GCSE physics unit 1 exam tomorrow and this has helped loads!

  2. may says:

    this did not help at all!!!!! :(

  3. MacB says:

    Re: May.

    What are you having trouble with in this subject matter?

  4. grrrrr says:

    did not help at all

  5. kenjay says:

    You didn’t answer my question! :(

  6. @kenjay

    What is your question?

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