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THERMAL (HEAT) ENERGY TRANSFERS - Coggle Diagram
THERMAL (HEAT) ENERGY TRANSFERS
CONDUCTION
In conduction, energy is transferred through a material from a warmer place to a cooler place without the material itself moving.
1.
If our finger touches a metal object, heat is conducted out of our finger and into the metal. It leaves our finger colder then before.
Why does this happens?
Because metal is a good
conductor
.
2.
If we touch a plastic object, heat conducts into the area that our finger is in direct contact with. The heat travels no further and our finger remains warm.
Why does this happens?
Because plastic is a good
insulator
.
BEST CONDUCTORS
: diamond, silver, copper, steel, aluminium
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CONVECTION
In convection, energy is transferred from a warmer place to a cooler one by the movement of the material itself.
This phenomenon can be observed in any fluid (liquid or gas)
An example of convection is the rising of hot air.
When air is heated, it expands (its volume increases while its density decreases). Since it is less dense than its surroundings, it floats upwards.
RADIATION
In radiation, thermal energy travels through empty space.
The Earth is bathed in various forms of electromagnetic radiation from the Sun, such as light, infrared radiation e ultraviolet radiation.
The hotter an object, the more
infrared radiation
it gives out.
Characteristics of infrared radiation:
it is produced by warm or hot objects
it is a form of electromagnetic radiation
it travels through empty space in the form of waves
it travels in straight lines
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CONSEQUENCES OF THERMAL (HEAT) ENERGY TRANSFERS
Energy tends to escape from a hot object.
To keep energy in something that is hotter than its surroundings, we need to insulate it.
Home insulation
Loft and underfloor insulating materials and cavity walls reduce heat losses by cunduction.
Thick curtains, draught excluders and foam or rockwool in wall cavity reduce heat losses by convection.
Double and triple glazing of windows reduce heat losses by conduction and convection.
Vacuum (thermos) flasks
They are used to keep hot drinks hot and cold drinks cold.
They are structured with a stopper, a metal or plastic case, a double-walled glass flask, insulating supports, a vacuum between walls and silvered inner surfaces.