P2.1 - Conduction. Flashcards
Metals conduct energy better than..
non-metals do
Copper is a better conductor than..
steel
Glass conducts better than..
wood
The best insulators are…
- non-metal materials
- eg wood/fibre glass
Conduction of energy depends on..
the material
The greater the thermal conductivity of a material…
the more energy per second it transfers by conduction
The bigger the temperature gradient…
the more thermal energy will be transferred
Energy transfer per second through a layer of insulating material depends on:
- temperature difference across the material
- thickness of the material
- thermal conductivity of the material
Good insulators have to have …
a low thermal conductivity
Why do good insulators have to have a low thermal conductivity?
so energy transfer through them is very low
Ways to increase insulation:
- thermal conductivity of material should be as low as possible
- thickness of material should be a thick as possible
Why are metals good conductors?
- metal atoms have many free electrons
- these move around/vibrate
- energy is transferred to neighbouring electrons like this
Why are metals cold to human touch?
because they are transferring the heat
- from you hand
- at a very fast pace
Why are some metals better conductors than others?
- atoms have different sizes/atomic weights
- which changes the pattern of thermal conductivity
Low thermal conductivity is caused by? (particles)
as there is less energy transfer between electrons
The rate of energy transfer in houses can be reduced by? (5 points)
- loft insulation
- cavity wall insulation
- double glazed windows
- aluminium foil behind radiators
- external walls thicker bricks and lower thermal conductivity
Loft insulation description
layer of insulating material over/under loft floor
Loft insulation process
- slows convection (warm air rising to the top of the house)
- through ceilings and then from escaping to outside
Convection
causes warm air to rise
Cavity wall insulation description
insulating layer between inner/outer walls
Cavity wall insulation process
-slows convection of heat from rooms to outside
Example of trapped heat being a great insulator
- padded jackets
- maintain body heat
Double glazing description
-2 panes of glass in window with air/vacuum in space between them
Double glazing process
- as air is a great insulator
- slows conduction of heat from rooms to outside through windows
- vacuum prevents convection of heat
Foil behind radiators description
-layer of reflective material on walls behind radiators
Foil behind radiators process
- reflects radiation back into room
- reduces rate of heat loss by radiation from radiators towards wall
Most common ways of heating homes:
- electric/gas heaters
- gas/oil-fired central heating
- solid fuel stores
