Infrared Radiation, Conduction and Convection
- Created by: Becka Sharp
- Created on: 14-06-14 15:37
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- Infrared Radiation, Convection and Conduction
- Convection
- Liquids and Gases Only
- When particles move from the hotter region to the cooler region and take their heat energy with them
- More effective than Convetion
- Convection Currents are all about Changes In Density
- Convection can't happen in solids as the particles can't move
- Convection is most efficient in roundish or squarish containers because they allow the convection currents to work best
- Because hot water rises (because of the low density) you only get convection currents in the water above the heater. The water below it stays cold because there's almost no conduction.
- Conduction
- Conduction occurs mainly in solids
- Conduction of heat energy is the process where vibrating particles pass on their extra kinetic energy to neighboring particles
- The process continue down the solid and gradually the heat passes all the way through the solid causing a rise in temperature at the other side of the solid
- Conduction occurs faster in denser solids, because the particles are closer together so collide more often and pass the energy between them
- Materials that have larger spaces between the particles conduct heat energy slower
- These materials are insulators
- Infrared Radiation
- Emission of electromagnetic waves
- All objects are continually emitting and absorbing infrared radiation
- An object that's hotter than its surroundings emits more radiation than it absorbs
- An object that is cooler than its surroundings absorbs more radiation than it admits
- The hotter an object is, the more radiation it radiates in a given time
- Dark, matt surfaces absorb infrared radiation falling on them much better than light, shiny surfaces such as gloss white and silver.
- They also emit much more infrared radiation (at any given temperature)
- Light, shiny surfaces reflect a lot of the infrared radiation falling on them.
- E.g Vacuum flasks have silver inner surfaces to keep heat in/out.
- Depending on whether it's storing hot or cold liquid
- E.g Vacuum flasks have silver inner surfaces to keep heat in/out.
- Solar hot water panels contain water pipes under a black surface
- Radiation from the Sun is absorbed by the black surface to heat the water in the pipes
- The water can be used for washing or pumped to heat the buildings
- Radiation from the Sun is absorbed by the black surface to heat the water in the pipes
- Convection
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