Understand that convection is an important method of thermal energy transfer in liquids and gases.
What is Convection?
Convection is the transfer of heat by the bulk movement of a fluid (liquid or gas). The fluid carries thermal energy from a hotter region to a cooler region as it circulates.
How Convection Works
When a portion of a fluid is heated, its temperature rises.
Heating reduces the fluid’s density (most fluids expand when heated).
The less‑dense, warmer fluid rises under the influence of gravity.
Cooler, denser fluid moves down to replace the rising warm fluid.
This continuous circulation creates a convection current.
Key Features
Requires a fluid medium – does not occur in solids.
Driven by differences in density caused by temperature gradients.
Can be natural (driven solely by buoyancy) or forced (driven by a pump or fan).
Examples of Convection
Boiling water in a kettle – hot water rises, cool water descends.
Atmospheric circulation – warm air rises at the equator, cool air sinks at the poles.
Heating a room with a radiator – warm air circulates around the room.
Ocean currents – warm surface water moves toward colder regions.
Factors Affecting the Rate of Convection
Factor
Effect on Convection
Temperature difference (ΔT)
Larger ΔT increases buoyancy forces, speeding up the flow.