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Energy Resources & Transfers, the transfer of energy by heating by…
Energy Resources & Transfers
energy stores
chemical
kinetic
gravitational potential
elastic potential
thermal
magnetic
electrostatic
nuclear
energy transfers
mechanically
by heating
electrically
by radiation (light and sound)
the principle of the conservation of energy
energy can be
stored or transferred
but can never be
created or destroyed
the total energy of a closed system has no net change
EQUATION:
efficiency = (100 x for percentage) useful energy output
/
total energy output
sankey diagrams
can be used to show how much of the input energy is useful, and how much is wasted
conduction, convection and radiation
the transfer of thermal radiation
conduction
- the process where vibrating particles transfer energy from their kinetic energy store to the kinetic store of neighbouring particles
mainly occurs in solids
metals are the best - free electrons
can be seen by attaching beads to a metal bar by wax (heat the opposite end of the bar, wax will melt, beads will fall off)
convection
- occurs when the more energetic particles move from the hotter region to the cooler region, transferring energy as they do
convection currents
occurs in kettles and hot water tanks
can be seen using coloured (potassium permanganate) crystals
radiation
- the only type of radiation that can occur through a vacuum
emission and absorption of radiation
temperature
hotter
objects
emit
more radiation
cooler
objects
absorb
more radiation
surface
black
surfaces are better at
absorbing and emitting
radiation than white surfaces
matt
surfaces are better at
absorbing and emitting
radiation than a shiny one
Leslie's cube
can be used to investigate the emission of thermal radiation
reducing unwanted energy transfer
insulation
EQUATION:
work done = force x distance moved
(work done = energy transferred) W = F x d
EQUATION:
gravitational potential = mass x gravitational field strength x height
GPE = mgh
EQUATION:
kinetic energy = 1/2 x mass x speed²
KE = 1/2 x m x v²
power
the rate of doing work / the rate of energy transfer
EQUATION:
power = work done
/
time
P = W
/
t
generating electricity
the transfer of energy by heating by infrared radiation
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