P2 - energy transfer by heating Flashcards
which is a better conductor, copper or steel
copper
what does the energy transfer/second through a layer of insulating material depend on?
temperature difference across material
thickness of material
thermal conductivity of material
how do you reduce energy transfer?
thermal conductivity of insulating material must be low
thickness of insulating material should be extremely thick
what is the relationship between the temperature of an object and it’s 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 all the radiation that hits it, and doesn’t reflect any or transmit any
what is the radiation emitted by a perfect black body called
black body radiation
what does an object that has a constant temperature emit
radiation across a continuous range of wavelenths
the same infrared radiation as it absorbs
what does the temperature of the earth depend on
the rate that light + infrared radiation from the sun are:
reflected back into space or absorbed by the earths atmosphere by the earths surface
emitted from the earths surface and from the earths atmosphere into space
what would happen if the earth had no atmosphere
the temperature on the surface will plunge to about -180 degrees C
what do gases like water vapour, methane and carbon dioxide (greenhouse gases) do
absorb longer wavelength infrared radiation from earth and prevent it from escaping into space
the amount a substances temperature rises by depends on
the amount of energy supplied to it
the mass of the substance
what the substance is
what is specific heat capacity
the energy needed to raise the temperature of 1kg of a substance by 1°C
what is a storage heater
a storage heater is uses electricity at night to heat special bricks or concrete blocks in the heater
how are houses heated
electric/gas heaters, oil, gas central heating systems, solid fuel in stoves or in fireplaces
how do you insulate a home
lost insulation (fibreglass) - it’s a good insulator, the air between the fibre helps reduce the rate of energy transfer by conduction
cavity wall insulation - insulation is pumped into the cavity, traps air in small pockets
aluminium foil between radiator panel and wall - reflects radiation away from the wall
double glazed windows - dry air vacuum is a good insulator
thicker bricks - lower energy transferred to outside
