physics 1a and 1b core foundation

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  • Created by: mn25
  • Created on: 04-05-16 11:35

HEAT RADIATION-

Heat is transferred by...

  •      conduction through solids
  •      convection through liquids and gases
  •      radiation through infrared

infrared- gives out electromagnetic waves:

  • all objects emit and absorb infrared radiation
  • hotter-more infrared radiation
  • hotter- emits more

                               bigger the temperature change, faster the heat is transferred.

  • cooler- absorbs more

radiation depends on the surface colour and texture:

  • dark/matt surface= good absorbers/emmitters
  • light/shiny= poor absorbers/emmitters but are good reflectors of radiation.

KINETIC THEORY AND CONDUTION

(http://physicsnet.co.uk/wp-content/uploads/2010/06/solid.jpg)solid- strong forces of attraction and are arranged into a pattern but done have much energy therefore they vibrate.

(http://physicsnet.co.uk/wp-content/uploads/2010/06/liquid.jpg)liquid- weak forces of attraction as are closer together but cannot move therefore they gain more energy then a solid particle.

(http://physicsnet.co.uk/wp-content/uploads/2010/06/gas.jpg)gas- no forces of attraction between particles as they have more energy therefore the particles are free to move in any direction.

CONDUCTION-Conduction occurs through solids- it is where vibrating particles pass on their energy to the particles next to them.

Materials with close packed particles are conductors.

  • materials with large spaces between particles will conduct slower.

CONVECTION-

Convection only occurs through liquids and gases only - it is when the particles with the most energy move from the hottest place to the cooler place taking all the heat energy with them.

Convection currents are all about the changes in density.

CONDENSATION AND EVAPORATION-

Condensation is when a gas turns into a liquid.

  • gas cools
  • particles slow down
  • particles lose energy
  • attractive forves become stronger
  • temperature is low

Evaporation is when a liquid turns into a gas.

  • particles with the most energy escape from the liquid
  • the temperature of the liquid falls and the liquid cools.

The speed can vary:

  • Evaporation:

+ The temperature is high

+ The density is low

+ The surface area is large

+ The airflow is greater

  • Condensation:

+ The temperature is low.

+ The surface area is larger

RATE OF HEAT TRANSFER

The rate an object transfers heat energy depends on...

  • The surface area and volume

          - The bigger the surface area, the more infrared waves can be emmittes or absorbed from the surface. This means heat transfer is quicker

          - If two objects at the same temperature have the same surface area but different volume, the object with the smaller volume will cool more quickly.    #

  • The materical of the object and what its touching.

          - Objects made from conductors will transfer heat more quickly than objects made from insulators therefore heat will

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