1Insulation slows energy transfer
Insulation slows down energy transfer. A coat doesn't make heat: it traps a layer of still air, which slows the energy escaping from your warm body.
insulation
Lesson 15.4 notes
Insulation
Insulators and trapped air, keeping homes warm, testing insulators, the vacuum flask, and animals.
2Trapped air
Many insulators trap air. Air is a very poor conductor, and trapped air can't flow, so there are no convection currents to carry energy away.
3Where a house loses heat
An uninsulated house loses about a third of its heat through the walls and about a quarter through the roof. The rest is lost through draughts, windows and the floor.
4Insulating a home
Loft insulation, cavity wall insulation, double glazing and draught excluders all trap air or stop it flowing. Less energy escapes, so heating bills fall.
loft insulationcavity walldouble glazing
5Testing insulators
Wrap identical beakers of hot water in different materials and record their temperatures. The water in the best insulator cools the slowest. Keep the volume and starting temperature the same.
6The vacuum flask
A vacuum flask has a vacuum between two glass walls, so there's no conduction or convection across it. Silvered walls reflect infrared, and the stopper keeps warm air in.
vacuum flask
7Animals keep warm
Animals insulate themselves too: fur and feathers trap air, seals and whales have thick blubber, and penguins huddle so that less of each body is open to the cold.
Explore: Insulate a house
Add loft insulation, cavity wall insulation, double glazing and more. See how much less heat escapes.
Common mistake: Insulation does not add heat
A coat doesn't give you energy. It slows down the transfer of energy from your warm body to the colder air. The same insulation keeps a cold drink cold.
Remember
- Insulation slows down energy transfer, usually by trapping still air.
- An uninsulated house loses the most heat through its walls and roof, so cavity wall and loft insulation help most.
- A vacuum flask: the vacuum stops conduction and convection; silvered walls reflect infrared radiation.
Going further at GCSE