SP3: conservation of energy Flashcards
mnemonic for types of energy store
naomi - nuclear
campbell - chemical
met - magnetic
grace - GPE
kelly - kinetic
to - thermal
eat - elastic potential
enchiladas - electrostatic
energy pathways
-mechanical work
-electrical work
-heating
-radiation
mechanical work
a force moving an object through a distance
electrical work
charges moving due to a potential difference
heating
due to temperature difference caused electrically or by chemical reaction
radiation
energy transferred as a wave
how long can energy stay in stores?
million of years or for fractions of a second
how often do energy transfers happen?
all the time
what is an energy transfer?
how energy is moved from one object to another
transfer diagrams
-the boxes show the energy stores
-arrows show the energy transfers
sankey diagrams
-sankey diagrams start off as one arrow that splits into two or more points
-this shows how all the energy in a system is transferred into different stores
-the width of the arrow is drawn to scale to show the amount of energy
can energy be created or destroyed?
no, it can only change in form or be dissipated
energy transfers in smartphone
-in use, the battery’s chemical energy store decreases
-the energy is transferred via the electrical work pathway to light the screen and produce sound
-the light that comes from a smartphone is emitted via the light radiation pathway, and the sound waves are emitted via the sound radiation pathway
GPE formula
mass × gravity × height
what is a system?
an object or group of objects
what is caused by the transfer of wasteful energy in mechanical processes?
a temperature rise, this energy is dissipated into the system
when is energy dissipated in a mechanical system?
-when two surfaces rub together
-work is done against friction and the two surfaces heat up, thermal energy increases and is transferred to the surroundings
examples of helpful & wasteful energy
kettle
(helpful) energy that heats the water (wasted) thermal energy heating the kettle
light bulb
(helpful) light radiation given out by the hot filament
(wasted) infrared radiation transferred to the surroundings
how can dissipation in devices be reduced?
lubrication being used to reduce the friction between moving parts of a machine, this reduces the thermal energy transferred
efficiency in devices
-a very efficient device will waste very little of its input energy
-a very inefficient device will waste most of its input energy
how are devices designed?
to waste as little energy as possible
efficiency formula
useful output/total input × 100%
why can’t efficiency be greater than 1 or 100%?
-this would mean that more energy is being transferred than is being supplied, which would mean that energy is being created
-this would break the law of conservation of energy
how can efficiency be improved in systems that are designed to transfer thermal energy?
by reducing the wasteful dissipation of thermal energy to the surroundings, for example by using insulation
why is increasing efficiency of heating of buildings important?
-the amount of energy required for heating can be very large
-thermal energy will transfer from inside warm buildings to the cooler surroundings outside
which materials are good for keeping houses warm?
poor conductors such as brick, wood, plastic and glass
what is thermal conductivity?
a measure of how quickly energy is transferred through a material via conduction
how can you reduce the transfer of thermal energy in buildings? (walls)
-the walls can be built thicker, so the energy must travel further before it is transferred to the outside
-two walls with an air gap between them, as air has a lower thermal conductivity than brick (cavity wall)
why is it good to have a window made of two layers of glass with a layer of air between them?
-both glass and air are insulators because they have low thermal conductivities
-the air has the lowest thermal conductivity and reduces the overall conductivity of the window unit
-air and glass are both transparent so people can still see through the windows
dissipation
the spreading out and transfer of energy stores into less useful forms
what are systems that can store lots of energy called?
energy resources
what are some major energy resources that can produce electricity?
fossil fuels, wind, hydroelectricity, water waves, the sun
patterns of energy use throughout the day
-during early evenings a lot of energy is needed for heating, lighting and cooking but overnight there is very little needed while people sleep
-during winter there is more heating and lighting required than in summertime
global energy consumption 2014
oil = 32%
gas = 24%
coal = 30%
nuclear = 4%
hydro = 7%
other = 3%
(fossil fuels = 86%)
why is most electricity still produced by fossil fuels?
-fossil fuels give out a high power output compared to other energy resources
-the existing infrastructure for extracting, transporting and processing fossil fuels (continuing to use this is cheaper than setting up new alternatives)
why is nuclear power stations use growing in developed countries?
-nuclear fuel can release large amounts of energy compared to fossil fuels and doesn’t emit carbon dioxide (however the radioactive waste that is produced is difficult to store and dispose of)
factors that affect governments’ decisions on the use of energy resources
-political and economic pressures
(eg:
-saudi arabia’s economy is heavily based in extracting and exporting oil it has a strong interest in fossil fuels being used to generate electricity)
how are renewable resources replenished?
-human action, eg trees cut down for biofuel are replaced by planting new trees
-natural processes, eg water let through a dam for hydroelectricity is replaced through the water cycle
what is a renewable resource?
one that can be replenished as it is used
what is a non-renewable resource?
a resource that can’t be replenished as it is being used
fossil fuels facts (energy store, uses, energy output, impact on enviro)
-non-renewable
energy store: chemical
uses: transport, heating, electricity generation
energy output: high
impact on enviro: causes global warming
nuclear fuels facts (energy store, uses, energy output, impact on enviro)
-non renewable
energy store: nuclear
uses: electricity generation
energy output: very high
impact on enviro: radioactive waste (needs to be disposed of safely)
biofuel facts (energy store, uses, energy output, impact on enviro)
-renewable
energy store: chemical
uses: transport, heating, electricity generation
energy output: medium
impact on enviro: carbon-neutral (low impact)
wind energy facts (energy store, uses, energy output, impact on enviro)
-renewable
energy store: kinetic
uses: electricity generation
energy output: very low
impact on enviro: take up areas that could be used for farming, said to spoil people’s view of scenery
hydroelectricity facts (energy store, uses, energy output, impact on enviro)
-renewable
energy store: gravitational potential
uses: electricity generation
power output: medium
impact on enviro: local habitats are affected by the large areas that need to be flooded for dams
geothermal energy facts (energy store, uses, energy output, impact on enviro)
-renewable
energy store: thermal
uses: electricity generation, heating
power output: medium
impact on enviro: very low
tidal energy facts (energy store, uses, energy output, impact on enviro)
-renewable
energy store: kinetic
uses: electricity generation
power output: potentially very high, but hard to harness
impact on enviro: tidal barrages can block sewage which needs to go out to sea
sun energy facts (energy store, uses, energy output, impact on enviro)
-renewable
energy store: nuclear
uses: electricity generation
power output: potentially very high, hard to harness
impact on enviro: very low
description of magnetic energy store:
energy stored when repelling poles have been pushed closer together or when attracting poles have been pulled further apart
description of internal energy store:
-the total kinetic and potential energy of the particles in an object
description of chemical energy store:
the energy stored in chemical bonds
description of kinetic energy store:
the energy of a moving object
description of electrostatic energy store:
the energy stored when repelling charges have been moved closer together or when attracting charges have been pulled further apart
description of GPE store:
the energy of an object at height
description of nuclear store:
the energy stored in the nucleus of an atom
