Convection

A convection current arises when less dense warmer air (water etc.) is forced upwards by buoyancy forces. Convection currents are fluid flows that carry heat - not heat flows.

Convection is an important mode of heat transfer in poor conductors such as air and water. Convection is the 'pump' that drives the fluid flow in passive solar water heaters, air conditioned rooms, and hurricanes.

If you want a solar water heater to work unassisted, put the hot water collection tank above the heat collecting pipes. If you want your upstairs bedroom to stay cool, close the door. If you want to avoid Hurricanes do not live on exposed coastlines, within 20° of the equator, where the sea temperature is above 26°C.

Convection in water is made visible with a suspension of plastic chips. Make your own bottle by cutting up 50 yoghurt pots and suspending the chips in brine.

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