P2 Flashcards
How are solar panels used
Solar panels absorb infrared radiation from the sun and is used to generate electricity directly or heat water.
in the northern hemisphere the solar panels are normally situated on the roof facing the south so it absorbs as much light as possible.
It’s used to heat homes using electricity or gas but can be expensive.
What must insulation materials have
Materials that are good insulators are necessary to keep you warm. They must have low conductivity so energy transfer is as low as possible.
What does the energy per second through a layer of insulating material depend on:
- temperature difference across a material
- thickness of the material
- thermal conductivity of a material
What ways reduce energy transfer as much as possible
- thermal conductivity of the insulating material should be as low as possible
- thickness should be as shuck as possible such as insulating a loft
When testing rods if different materials as conductors what must be kept the same CV
Rods need to be same length/width
For a fair test each rod is coated with a wax near one end
The unwaxed area in the other end is heated
The wax melts fastest on the rods is due to…
Metal conducts energy better than non-metals
Copper is a better conductor than steal
Glass conducts better than wood
What is thermal conductivity
In terms of the testing rod experiment
Each rod has the same temperature difference between its ends. The energy is transferred by conduction through a material depending on its thermal conductivity.
What is specific heat capacity
Increasing the temp of 1kg of water by 1(degrees) requires 1000J of energy l: More accurate measurements would give 4200J per Kg per degree for water. This is SHC. The energy needed to increase the temperature of something.
What’s the equation for energy transfer
Energy transfer= mass x SHC x temp change
How does loft insulating help reduce rate of energy transfer at home
Such as fibre glass reduces rate if energy transfer through the roof.
Fibre glass JD a good insulator as the air between the fibre reduces energy transfer by conduction
The greater number of layers crates a thicker insulation so rate if energy transfer decreases
How does a cavity walk below reduce the rate if energy transfer at home
It reduces energy transfer from the outer walls if the house. It’s placed between 2 brick walls and traps air in small pockets reducing energy transfer by conduction.
How does aluminium foil reduce energy transfer in the house
Between radiation label and a walk if reflects radiation away from the wall reducing rate of Ernest transfer by radiation.
How does double glazed windows help reduce we get transfer in a home
2 glass panels with a vacuum. Thicker the glass the lower the thermal conductivity. Dry air reduces rate of energy transfer by conduction and convection.
How does in external walls reduce energy transfer in a home
Thicker walls/brick had lower thermal conductivity from the inside of the building to the outside so cost of living will be less
