Energy transfers Flashcards
Convection, conduction, radiation and insulation
What are the three methods of energy transfers
Convection, conduction and radiation
Where does thermal energy move from
A hot area to a cold area
Are liquids and gases good or bad conductors
bad
How does thermal energy transfer via conduction
Atoms in a solid vibrate if a part of the solid is heated, atoms vibrate more vigorously, atoms collide into neighboring atoms making them vibrate more vigorously, because intermolecular forces are stronger in solids increased vibrations are passed on
Why are metals a better conductor of thermal energy
Metals have a sea of free electrons so they are free to move, so when electrons gain thermal energy they increaese their velocities and move over distances more quickly, leading to a FASTER RATE OF CONDUCTION
Explain how are fire can heat up a whole room and name the process
- Fire heats air above it
- air expands, becomes less dense and rises
- cooler more dense air is drawn in to takes its place
- the process repeats
CONVECTION CURRENT
In a experiment why would you stir a beaker of heated water before taking its temperature
You would stir beaker to mix up the convection currents so all parts of liquid are the same temperature
What is infra red radiation
electromagnetic waves
How does temperature effect radiation
The HIGHER the temperature the more radiation emitted
What does radiation not need to travel
A medium - it can travel through a vacuum
What are good absorbers of IR radiation
Dull black surfaces
What are good reflectors of IR radiation
Shiny silver surfaces
What are the best and worst emitters of IR radiation
Dull black surfaces - best
Shiny silver - worst
What does the object have to be to emit IR radiation
Hotter then the surroundings
Why do birds use feathers to stay warm
Feathers trap air which is a good insulator, and this also means convection currents can’t occur
How do layers of clothing, loft insulation, double glazing and cavity walls all provide insulation (prevent energy loss)
Trap air which is a good insulator and stoop the air circulating which prevents a convection current being set up
How does a thermos prevent energy loss
- Shiny surfaces inside to reflect IR radiation back in
- Silver surface on outside to reduce IR radiation being emitted
How does a vacuum prevent thermal energy loss
there are no particles no neither conduction or convection can occur
What are the energy stores
- kinetic
- Gravitational potential
- chemical
- Elastic potential
- magnetic
- electrostatic
- Nuclear
- Thermal
What are the energy transfers/pathways
- Heating
- Electrically
- Radiation
- Mechanically
What is the equation for efficiency
efficiency = useful energy output/ total energy input x 100
What does Gravitational Potential energy equal
mass x gravity x height
gravity = 10
What is GPE measured in
Joules
How does GPE increase
When work is done to it
