Convection Currents
Physics: Cambridge International GCSE Supplement, topic 2.3.3
Convection
Liquids and gases are called fluids because they can flow. They do not conduct heat well, but they can transfer heat energy using convection currents. Convection currents are created by areas of different densities in a fluid. They work like this:
Stage 1
- When part of a fluid is heated, the particles in this area gain kinetic energy.
- When the particles gain kinetic energy they move away from each other, so the area that has been heated becomes less dense and the warm fluid particles rise.
Stage 2
- The warm fluid rises and transfers some thermal energy to nearby fluid.
- As a consequence the warm fluid becomes less dense and starts to sink.
Stage 3
- At the bottom, colder parts of the fluid that hasn’t been heated yet will replace the warm fluid that has risen.
- These colder particles are then heated. They move apart and start to rise.
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Stage 4
- This cycle creates convection currents. Convection currents are the result of different densities in the fluid. These different densities are created by heating.
Convection Currents - Examples
Convection currents are used in:
Radiators
- In colder countries, most homes have heaters (called radiators) fixed at around floor level.
- They heat rooms using convection currents. The warm air rises and pushes cold air down to floor level, where it is heated up by the radiator.
Air Conditioning
- In hot countries, most homes have air conditioning (AC) units fixed at the top of the wall.
- Hot air rises up to where the AC unit is fixed. It is cooled down and falls, pushing up more hot air to be cooled by the air conditioning unit.
Weather
- Convection currents can create wind, clouds and other more extreme weather in the atmosphere.
Test yourself on Convection Currents
Which of the following are true of convection currents in a kettle?
What causes convection currents?
Convection Currents
What can cause extreme weather events?
Suggest how hot air balloons work.