P2: Energy transfer by heating Flashcards
good insulators have a….
low thermal conductivity
how can we make an insulator as good as possible
-lowest conductivity
-thick as possible
what is the energy we absorb from the sun
infrared radiation
how does temperature affect infrared radiation
the higher the temperature of an object, the more infrared radiation it emits in a given time
what is a perfect black body
an object that absorbs and emits all radiation.
what is the radiation that a black body emits
black body radiation
an object that has a constant temperature…
emits radiation across a continuous range of wavelengths.
how can we use infrared radiation?
-rescue blankets, shiny surface emits less than absorbed, staying warm
-thermal imaging cameras
how does infrared affect the earth’s temperature
-more reflected light means colder temps, more absorbed means warmer.
-more emitted from the Earth’s surface means warmer
how does the absorption and emission of infrared work
- infrared radiation from the Sun warms the ground
- ground becomes warm and emits longer-wavelength infrared radiation
- CO2 molecules absorb and re-emit infrared radiation back into the ground.
what is specific heat capacity
the energy needed to raise the temperature of 1kg of the substance by 1 degrees celsius
unit of specific heat capacity
J/kg degrees celsius
how do storage heaters work
uses electricity at night to heat special bricks and concrete blocks in the heater.
energy transfer keeps the room warm.
bricks have higher specific heat capacity, slowly warm up and cool down.
how can we insulate a home
-loft insulation
-cavity wall insulation
-aluminium foil between radiator and wall
-double glazed windows
-thicker bricks
loft insulation
e.g. fibreglass
reduces the rate of energy transfer through the roof.
cavity wall insulation
reduces energy transfer out the walls of the house. placed in between two layers of brick that make up the wall.
traps air in small pockets, reducing rate of energy transfer by conduction
aluminium foil
reflects radiation away from the wall and reduces energy transfer by radiation
double-glazed windows
thicker glass means lower thermal conductivity, meaning slower energy transfer.
Dry air is also good insulator.
Vacuum prevents energy transfer by convection.
how can we use infrared as energy
solar panels
