P2 - Energy Flashcards
Best conductors is energy?
Metals.
Best insulators?
Non metals - fibreglass, wool etc.
Thermal conductivity?
Rate of energy transfer through an object. The higher the thermal conductivity he higher the rate of energy transfer.
Insulation slows down the…
Rate of transfer of energy.
Factors that impact the energy transfer per second through a layer of insulation?
Temp difference across the material
Thickness
Thermal conductivity of the material. (Lower the better)
Where is infrared radiation from?
The sun. (All of them are 😂)
Which emits more IR radiation;
A cold object
A warm object
A warm. The hotter the temp the more IR radiation It emits.
Constant temp?
Emits IR radiation at the same rate that absorbs it.
Perfect black body?
TRIPLE
An object that absorbs all radiation that hits it. Also the best possible emitter.
Black body radiation = radiation emitted by a black body.
Why do objects change colour when they heat up?
Because at first it emits only IR radiation, but as it gets hotter it changes to red, then orange, then white because as it emits more radiation at shorter wavelengths as it gets hotter.
Specific heat capacity?
Energy needed to raise 1kg of a substance by 1 degree C.
How does the mass of the object effect the rate of heating?
The greater the mass of the object, the slower the rate of temperature increase.
Rate of transfer of energy from houses can be reduced by….
- loft insulation - fibreglass, traps air, insulated
- cavity wall insulation
- double glazed windows
- aluminium foil behind radiators - reflects radiation away from the wall.
- external walls with thicker bricks and a lower thermal conductivity - makes rate of transfer from inside to out less.
Order of Electromagnetic spectrum?
Radio Micro Infrared Visible light Ultraviolet X-rays Gamma
Which type of electromagnetic radiation has the longest wavelength and the lowest frequency?
Radio waves
