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PHYSICS > SP3: conservation of energy > Flashcards

SP3: conservation of energy Flashcards

1
Q

mnemonic for types of energy store

A

naomi - nuclear
campbell - chemical
met - magnetic
grace - GPE
kelly - kinetic
to - thermal
eat - elastic potential
enchiladas - electrostatic

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2
Q

energy pathways

A

-mechanical work
-electrical work
-heating
-radiation

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3
Q

mechanical work

A

a force moving an object through a distance

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4
Q

electrical work

A

charges moving due to a potential difference

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5
Q

heating

A

due to temperature difference caused electrically or by chemical reaction

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6
Q

radiation

A

energy transferred as a wave

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7
Q

how long can energy stay in stores?

A

million of years or for fractions of a second

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8
Q

how often do energy transfers happen?

A

all the time

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9
Q

what is an energy transfer?

A

how energy is moved from one object to another

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10
Q

transfer diagrams

A

-the boxes show the energy stores
-arrows show the energy transfers

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11
Q

sankey diagrams

A

-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

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12
Q

can energy be created or destroyed?

A

no, it can only change in form or be dissipated

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13
Q

energy transfers in smartphone

A

-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

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14
Q

GPE formula

A

mass × gravity × height

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15
Q

what is a system?

A

an object or group of objects

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16
Q

what is caused by the transfer of wasteful energy in mechanical processes?

A

a temperature rise, this energy is dissipated into the system

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17
Q

when is energy dissipated in a mechanical system?

A

-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

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18
Q

examples of helpful & wasteful energy

A

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

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19
Q

how can dissipation in devices be reduced?

A

lubrication being used to reduce the friction between moving parts of a machine, this reduces the thermal energy transferred

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20
Q

efficiency in devices

A

-a very efficient device will waste very little of its input energy
-a very inefficient device will waste most of its input energy

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21
Q

how are devices designed?

A

to waste as little energy as possible

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22
Q

efficiency formula

A

useful output/total input × 100%

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23
Q

why can’t efficiency be greater than 1 or 100%?

A

-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

24
Q

how can efficiency be improved in systems that are designed to transfer thermal energy?

A

by reducing the wasteful dissipation of thermal energy to the surroundings, for example by using insulation

25
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
26
which materials are good for keeping houses warm?
poor conductors such as brick, wood, plastic and glass
27
what is thermal conductivity?
a measure of how quickly energy is transferred through a material via conduction
28
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)
29
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
30
dissipation
the spreading out and transfer of energy stores into less useful forms
31
what are systems that can store lots of energy called?
energy resources
32
what are some major energy resources that can produce electricity?
fossil fuels, wind, hydroelectricity, water waves, the sun
33
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
34
global energy consumption 2014
oil = 32% gas = 24% coal = 30% nuclear = 4% hydro = 7% other = 3% (fossil fuels = 86%)
35
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)
36
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)
37
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)
38
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
39
what is a renewable resource?
one that can be replenished as it is used
40
what is a non-renewable resource?
a resource that can't be replenished as it is being used
41
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
42
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)
43
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)
44
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
45
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
46
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
47
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
48
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
49
description of magnetic energy store:
energy stored when repelling poles have been pushed closer together or when attracting poles have been pulled further apart
50
description of internal energy store:
-the total kinetic and potential energy of the particles in an object
51
description of chemical energy store:
the energy stored in chemical bonds
52
description of kinetic energy store:
the energy of a moving object
53
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
54
description of GPE store:
the energy of an object at height
55
description of nuclear store:
the energy stored in the nucleus of an atom

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