大象传媒

Work, power and efficiency - CCEAReducing unwanted energy transfer

When work is done on an object, energy is transferred. Power is the amount of work done in one second. Efficiency is a measure of how much useful energy is converted.

Part of Combined ScienceEnergy

Reducing unwanted energy transfer

There are two main ways to reduce unwanted energy transfers by heating:

  • use - materials with low ;
  • use thicker materials.

The table shows some ways in which this is achieved in homes and other buildings.

MethodDetails
Cavity wallA gap between two brick walls contains air, which has a lower thermal conductivity than brick.
Cavity wall insulationThe gap between two brick walls is filled with material that has a lower thermal conductivity than air.
Loft insulationA thick layer of material with a low thermal conductivity reduces the rate of heat transfer through the ceiling.
Double glazed windowsA gap between two panes of glass contains air or another gas, which has a lower thermal conductivity than glass.
MethodCavity wall
DetailsA gap between two brick walls contains air, which has a lower thermal conductivity than brick.
MethodCavity wall insulation
DetailsThe gap between two brick walls is filled with material that has a lower thermal conductivity than air.
MethodLoft insulation
DetailsA thick layer of material with a low thermal conductivity reduces the rate of heat transfer through the ceiling.
MethodDouble glazed windows
DetailsA gap between two panes of glass contains air or another gas, which has a lower thermal conductivity than glass.