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section 4: Energy resources & energy transfers original (work and…
section 4: Energy resources & energy transfers original
Units
mass=kilogram (kg)
energy=joule (J)
distance=metre (m)
speed=metre/second (m/s)
force=newton (N)
power=watt (w)
time=seconds (s)
acceleration=metre/second squared (m/s² )
energy resources and electricity generation
various renewable and non-renewable methods of large-scale electricity production
see separate spider diagram
Energy transfers
herm
radiation
mechanically
electrically
heating
efficiency = (useful energy output ÷ total energy input) × 100%
sankey diagrams
energy efficiency is a measure of how usefully energy is converted by a device
as the useful energy output can never be greater than the energy input the efficiency can never be greater than 1.0
houses-insulation
power stations
law of conservation of energy
energy cannot be created or destroyed, it can only be transferred from one form to another
Energy stores
cakehelps
chemical energy= this is the energy that is released when chemical reactions take place
sound energy= this is the energy in the form of a sound wave
atomic energy (nuclear)= energy that is released when nuclear reactions take place e.g. the sun's energy
potential (gravitational)= this is the energy possessed by an object increased when it is raised up
kinetic energy= this is the energy possessed by a moving objects
light energy= this is the energy in the form of visible electromagnetic radiation
elastic potential= stored in a stretched or squashed object
electrical energy= this is the energy transferred by an electric current
heat (thermal) energy= this is the energy of an object due to its
temperature
work and power
work done= force × distance moved
w=f × d
work done is equal to energy transferred
power=work done ÷ time taken
gravitational potential energy=mass x gravitational field strength x height
GPE=m x g x h
kinetic energy=1/2 x mass x speed²
KE=1/2 x m x v²
GPE is a way of storing kinetic energy. You have to put work in to move something to increase its gravitational potential energy, and that energy is only released when the object falls (movement again)
kinetic energy gained=gravitational potential energy lost
power is the rate of doing work i.e. how much per second
heat energy
conduction= particles that are very close together can transfer heat energy as they vibrate. Transfer in solids not liquids or gases. metals=good conductors of heat.
during heat transfer thermal energy always moves in the same direction. Heat energy only flows when there is a temperature difference from a warmer area to a cooler area
convection= the heat transfer in gases and liquids involving the transfer of energy by particles. It can take place in a fidge, an oven or even the vacuum of space. good experiment-purple crystals + vacuum flask
radiation= thermal radiation is a type of electromagnetic radiation that involves infrared waves. No particles are involved, unlike in the processes of conduction and convection. Can occur in solids, liquids or gases. Object hotter than its surroundings emits more radiation than it absorbs (as it cools down). Object cooler than it surroundings absorbs more radiation than it emits (warms up)
reducing unwanted energy transfer
insulation
draught proofing
loft insulation
cavity wall insulation
double-glazing
thatched roof
foil behind radiatiors
payback time
the time taken to get your money back in savings
payback time=cost of insulator (£) ÷ annual fuel savings (£/yr)
