Chapter 1.5 - 'Convection' Flashcards
Briefly explain the concept of ‘convection’.
The transfer of thermal energy within a gas or liquid through a mass movement of particles within a system over a distance.
Explain why colder molecules sink.
The energy within hotter molecules pushes the particles apart through kinetic energy. This causes the density of the hotter molecules to decrease and so the colder molecules which are denser and heavier therefore fall and push the hotter molecules upwards.
State the variables impacting the rate of convection.
Temperature difference between the heat source and convective gas/ fluid.
Surface area exposed to convective fluid.
State and define the two main causes of convection.
Forced convection - Ducted heating in which air is heated and then blown into a room.
Natural convection - When a fluid or gas rises as it is heated.
Explain the concept of ‘Wind chill’.
The wind blows away the relatively thin layer of relatively still air near the skin that would normally act as a partial insulator. Cooler air comes into contact with the skin and heat loss increases.
Increases when the body or clothing is wet as evaporation occurs.
Explain the concept of ‘thermals’.
Give examples.
Columns or rising not air created by dark regions on the ground that have been heated up by the sun.
Roads, rock faces and ploughed fields.
