chapter 2 Flashcards
describe the rod test to test thermal conductivity
The rods need to be the same width and length for it to be a fair test. Each rod is coated with a thin layer of wax near one end, the uncoated ends are then heated together. The wax then melts fastest on the one with that best conducts energy.
what conducts energy better. Metals or non metals
metals
what is a batter conductor copper or steel
copper
what is a better conductor , glass or wood
glass
what does a greater thermal conductivity mean
the more energy per second it transfers by conduction
what type of thermal conductivity do insulators need to have and why
a low thermal conductivity, so the energy transfer through them is as low as possible
what does the energy transfer per second through a layer of insulating material depend on
temperature difference across the material, thickness, thermal conductivity of the material
what 2 ways reduce energy transfer as much as possible
the thermal conductivity being as low as possible, the material should be as thick as it can be
what type of radiation comes from the sun
infrared radiation
what happens to the wavelength of visible light spectrum as you go from blue to red light
it increases
which has a longer wavelength infrared or visible light
infrared
what does a higher temperature of an object mean
the more infrared radiation it gives out in a given time
what is a body
object
how does a body have an constant temperature
when it emits infrared radiation at the same rate it absorbs it
what is a perfect black body
an object that absorbs all the radiation that hits it , it doesn’t reflect any radiation and doesn’t transmit any (no radiation passes through it )
what is a good absorber also
a good emitter
what else is a perfect black body, other than absorbing all infrared radiation
a good emitter
what is the radiation emitted by a black body called
black body radiation
what is the relationship between an object having a constant temperature and the wavelength’s it emits
it emits radiation across a continuous range of wavelengths
what happens to the intensity of wavelengths an object emits if its temperature is increased
the intensity of the radiation it emits is greater at every wavelength
what happens to the increase in intensity of radiation emitted when there is a shorter wavelength of radiation
there is a greater increase in intensity at that wavelength
how does an objects temperature increase
when it absorbs radiation faster than it emits it
why do rescue teams use light coloured shiny blankets (foil) to keep people warm
a light shiny surface emits less radiation then a dark matt surface- this keeps the person warm
What factors affect the Earth’s temperature in relation to radiation from the Sun?
How much light and infrared radiation from the Sun is reflected back into space or absorbed by the Earth’s atmosphere or surface.
How much radiation is emitted from the Earth’s surface and atmosphere into space.
what would happen to the temperature if the earth had no atmosphere and why
it would go really cold - particles in the atmosphere re-emit infrared radiation back into the ground, without the atmosphere the surface would emit radiation back into space
what gasses absorb longer wavelength radiation and prevent it escaping into space, and what is this effect
water vapour, methane and carbon dioxide. The process makes the earth warmer than it would be if these gases weren’t in the atmosphere, as they emit radiation into the earths surface
what does an experiment on a substances temperature rise depend on
that amount of energy supplied, mass of substance, what the substance is
what is specific heat capacity
the energy needed to raise the temperature of 1kg of the substance by 1 degree Celsius
what is equation for energy transferred
energy transferred=mass x specific heat capacity x temperature change
what are ways you can reduce the rate of energy transfer at home
loft insulation, thicker bricks with lower thermal conductivity, double glazed windows, aluminum foil between a radiator panel and the wall
what is a loft insulation material and why is it good
fiberglass - It is a good insulator as the air between the fibers reduces the rate of energy transfer through conduction. The thicker the insulation the lower the rate of energy transfer is
how does cavity wall insulation work
it traps air in small pockets, reducing the rate of energy transfer by conduction
how do double glazed windows work
they are 2 layers of glass with dry air or a vacuum between the layers. The thicker the glass the lower the rate of energy transfer by conduction will be
how do thicker bricks help
they lower the rate of energy transfer from in the building
what do solar panels do
absorb infrared radiation from the sun to generate electricity (solar cell panels) or to heat water ( solar heating panels)
