P2.5 - Heating And Insulating Buildings (Finished) Flashcards
What can reduce frictional forces?
Lubrication
How does loft insulation work and give an example?
The air between fibres of fibreglass helps reduce energy transfer rate by conduction and is also a good insulator
How does cavity wall insulation work?
Cavity walls have an inner and outer wall with insulation (foam) pumped in between. It traps air in small pockets reducing the rate of energy transfer by conduction
How do double glazed windows work?
They have an inner and outer glass with dry air or a vacuum in the middle which reduces the energy transfer by conduction as dry air is a good insulator and a vacuum prevents transfer by convection
How does aluminium foil between radiator and wall reduce energy loss?
Reflects radiation away from the wall, so reduces energy transfer by radiation
How can external walls of a house be used to reduce energy transfer?
Using thicker bricks and bricks with a low thermal conductivity
How can solar panels be used to heat a building?
Solar panels will absorb infrared radiation from the sun and can be used to heat water directly to use for heating
What is convection?
Where energetic particles move away from hotter regions to cooler regions
Describe the process of convection?
1) Energy is transferred by heating to a gas/liquid’s thermal energy store
2) This is shared across the kinetic energy of the particles
3) These particles vibrate faster and therefore increase the space between them causing the region’s density to decrease
4) Warmer less dense region will rise above cooler region
How does a radiator heat a room?
1) Radiator transfers energy to air particles by conduction
2) When that air rises (explain) cooler air replaces it being heated
3) previously heated air transfers energy to surroundings, cools, sinks
Makes a convection current
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