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Unit 4 - Energy Transfers - Coggle Diagram
Unit 4 - Energy Transfers
conduction
the transfer of thermal (heat) energy through a substance by the vibration of atoms within said substance
as a result of the different states of matter having different particle arrangements, each state conducts differently
solids - good conductors ( particles close together so transfer energy more quickly)
and just because, some materials conduct heat better than others too
for example, copper is a good conductor of heat, found on the base of cooking pans in heat exchanges
steel is not a good conductor, and is found in high temperature environments such as aeroplane engines
liquids - bad conductor ( particles still close together but can be compressed, and therefore separated )
gases - extremely bad conductors (particles very far away from each the so cannot transfer vibrations to each other very fast
covection
when particles with high levels of energy in a liquid/gas move and take the place of particles with less heat energy
warm, less dense particles rise when heated in a container, and colder, more dense particles take their place to then be heated an rise themselves
this creates a 'convection current' when the particles continuously warm up, rise, get colder, and fall again to be heated up once more
radiation
the transfer of radiation by IR (infrared) waves
shiny, bright surfaces are radiate and absorb heat poorly
matte, dark surfaces radiate and absorb heat well
Power
Power (W) = Work done (J) / time (s)
P = W/t
W = P * t
t = W/P
Power is a measure of how quickly work is being done, and therefore how quickly energy is being transferred
Power = current * voltage
P = I * V
Work Done
work (J) = force (N) * distance moved (m)
W = F * d
also the same as amount of energy transferred
lifting:
change in GPE = work done
pushing
change in kinetic energy = work done
Efficiency
efficiency = (useful energy output/total energy output) * 100
the proportion of energy supplied that is transferred in useful ways
e.g Television
input - 200000 J
light energy - 12000
sound energy - 6000
efficiency = 18000/20000
efficiency = 90%
Units
Power - Watts (J)
Energy/Work - Joules (J)
distance - metres (m)
velocity - metres per second (m/s)
force - Newtons (N)
mass - kilograms (kg)
time - seconds (s)
efficiency - per 100 (%)
Energy transfers
ways of being presented
Sankey diagrams
energy transfer diagram
stores
kinetic
thermal(heat)
chemical
magnetic
electrostatic
gravitational (GPE)
kinetic
nuclear
elastic
ways of being transferred
mechanically
when a force acts on a body
through
radiation
light and sound: carries energy via the vibration between particles, and can therefore transfer it between places
heating
thermal energy can be transferred by convection, conduction and thermal radiation
electrically
electricity can transfer energy from a power source
Gravitational Potential Energy and Kinetic Energy
KE = 1/2 x mass (kg) x velocity^2 (m/s)
GPE = g x mass (kg) x height (m)
g = gravitational field strength (always 10 on earth)