energy transfer by heating Flashcards
2 (29 cards)
which materials conduct best
metals conduct better than non metals
copper conducts better than steel
glass conducts better than wood
how to do you compare conductors in a practical
rods same width and length
rods coated with thin layer of wax on one end
wax melts fastest on best conductor
the greater the thermal conductivity of an object…
the more energy per second it transfers by conduction
what is thermal conductivity
a measure of how well a material conducts energy when it is heated
The energy transfer per second through a layer of insulating material depends on
the temperature difference across the material
the thickness of the material
the thermal conductivity of the material
what do good insulators need to have
- a low thermal conductivity
- as thick as possible
What kind of material makes a good insulator
- non metals
- wool and fibreglass
the higher the temperature of an object…
the more infrared radiation it emits in a given time
what do all objects emit and absorb
infrared radiation
how can you conduct a practical to detect infrared radiation
- glass prism splits a narrow beam of white light into the colours of the spectrum
- thermometer reading rises when placed just beyond red part of spectrum because some of the IR in the beam goes there
a body at a constant temperature …
emits infrared radiation at the same rate it absorbs it
what is a black body
- an object that absorbs all radiation that hits it (doesn’t reflect or transmit any radiation)
- best possible emitter
- emits black body radiation
an object that has a constant temperature emits radiation across
a continuous range of
wavelengths
if the temperature of the object is increased
the intensity of the radiation it emits is greater at every wavelength
the shorter the wavelength of the radiation
the greater the increase in intensity in that wavelength. so peak intensity is at a shorter wavelength at a higher temperature than in was at the lower temperature.
if an object has a constant temperature, the objects emits infrared radiation at
the same rate it absorbs it
a light coloured, shiny blanket emits a lot less radiation than a dark, matt surface. True or False?
True - this keeps the patient warm
what factors affect the temperature of the earth?
the rate that light and infrared from the sun are:
- reflected back into space or absorbed by the earths atmosphere or surface
- emitted from the earths surface and atmosphere into space
what wavelength do greenhouse gases absorb
longer wavelength reflecting off the earths surface
what factors does temperature rise depend on
- amount of energy supplied to it
- mass of the substance
- what the substance is
what is the definition of specific heat capacity
the energy needed to raise the temperature of 1kg of a substance by 1 degree
what is the equation for specific heat capacity
for a known change of temperature of a known mass of a substance
energy transferred = mass * shc * temperature change
what are the units for shc
J/kg’C
the energy transferred to the substance increases the…
thermal energy store of the substance by an equal amount
