Thermal Conductivity (OCR GCSE Physics A (Gateway))

Thermal Conductivity

• Thermal conduction is the process where energy is transferred by vibrating particles in a substance

• The vibrating particles transfer energy from their kinetic store to the kinetic store of neighbouring particles

• The direction of energy transfer is always from hot to cold

• The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across the material

• Materials with high thermal conductivity heat up faster than materials with low thermal conductivity

Materials with high and low thermal conductivity

Insulating a Building

• Insulating the loft of a house lowers its rate of cooling, meaning less energy is lost to the outside

• The insulation is often made from fibreglass (or glass fibre)

  • This is a reinforced plastic material composed of woven material with glass fibres laid across and held together

  • The air trapped between the fibres makes it a good insulator

• It has a much lower thermal conductivity than the roof material

• Several layers of insulation make it very thick and therefore decrease the rate of cooling

Less heat is lost from a building with the help of insulation (filled cavity in walls) 

• Another aspect that affects the cooling of buildings is the walls

• Houses in cold countries are fitted with cavity wall insulation which is made from blown mineral fibre filled with gas

  • This lowers the conduction of heat through the walls from the inside to the outside