Edexcel IGCSE Physics: Double Science 复习笔记：4.1.6 Reducing Energy Loss

• Energy loss can be reduced by doing one of two things:
  • By reducing the amount of unwanted (wasted) energy that is produced
  • By preventing the energy from dissipating (if, for example, it has been produced deliberately)

   

Insulation

• In many situations, the heat that is produced is wanted. For example:
  • When heating a home
  • When boiling a kettle

   

• If this heat can be prevented from dissipating, then less thermal energy will be needed to replace the heat that has been lost
  • This can be achieved by surrounding the appliance with insulation

   

• The effectiveness of insulation depends upon:
  • How well the insulation conducts heat
  • How thick the insulation is

   

• Insulating the loft of a house lowers its rate of cooling, meaning less heat 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 rate of energy lost as heat is through 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