Energy Flashcards
(135 cards)
1
Q
is energy ever used up ?
A
no, just transferred between different energy stores and different objects
2
Q
which are the energy stores ?
A
thermal energy stores
kinetic energy stores
gravitational potential energy stores
elastic potential energy stores
chemical energy stores
magnetic energy stores
electrostatic energy stores
nuclear energy stores
3
Q
how is energy transferred?
A
mechanically (doing work)
electrically (work done by moving charges)
heating
radiation
4
Q
what happens when a system changes?
A
energy is transferred
5
Q
what is a closed system?
A
systems where neither matter nor energy can enter or leave
net change in total energy is always zero
6
Q
what is work done?
A
energy transferred
7
Q
when can work be done?
A
when current flows
a force moving an object
8
Q
what happens when a falling object has no air resistance?
A
energy lost from gpe store = energy gained in the kinetic energy store
9
Q
what happens to a falling object with air resistance?
A
energy is transferred to other stores of the object and surroundings
10
Q
kinetic energy equation
A
kinetic energy = 1/2 x m x v^2
11
Q
gravitational potential energy equation
A
gpe= m x g x h
12
Q
elastic potential energy equation
A
elastic potential = 1/2 x spring constant x extension^2
13
Q
what is specific heat capacity
A
the amount of energy needed to raise the temperature of 1kg of a substance by 1 degree
14
Q
why do some materials have different specific heat capacities
A
more energy needs to be transferred to thermal energy store to increase temp than others
materials that need to gain energy to warm up transfer energy to cool down so can store lots of energy
15
Q
specific heat capacity equation
A
change in energy = mass x specific heat capacity x temp change
16
Q
what is the law of conservation of energy
A
energy can be transferred, stored or dissipated but never created or destroyed
17
Q
what is power
A
the rate at which energy is transferred or the rate at which work is done
18
Q
power equation
A
power = energy transferred / time
19
Q
what is a watt
A
1 joule of energy transferred per second
20
Q
how does lubrication reduce energy waste
A
oil in a motor
reduces friction
less energy is lost as heat through friction
21
Q
how does thermal insulation reduce energy waste
A
double glazing
less useful thermal energy is lost
22
Q
what is conduction
A
the process where vibrating particles transfer energy to neighbouring particles
23
Q
what happens when the thermal conductivity of a material is high
A
heat is allowed to travel through the material more easily
rate of energy transfer by conduction is higher
24
Q
what would happen to heat in a building with thin metal walls
A
lost very quickly
25
what would happen to heat in a building with thick walls
rate of cooling is low
thermal conductivity low
26
what is convection
when energetic particles move away from hotter to cooler regions
27
where can convection happen
gases and liquids
28
how do radiators heat a room
create convection currents in the air of the room
29
what is the difference between convection and conduction
convection particles move by taking their energy with them
conduction vibrating particles transfer energy to other particles
30
what are the two ways to reduce unwanted energy transfers
lubrication
thermal insulation
31
how does lubrication avoid wasting energy
reduces frictional forces
32
how does insulation reduce unwanted energy transfers
heating
33
what are the examples of thermal insulation in houses
cavity walls (air gap or foam)
loft insulation (fibreglass wool)
double glazed windows
draught excluders (around doors and windows to avoid convection)
34
efficiency equation
efficiency = useful energy output/ total energy input
35
how can efficiency of a system be increased
reducing waste output (lubrication, thermal insulation)
recycling waste output ( absorbing thermal waste and recycling as input energy)
36
what are the non renewable energy sources
fossil fuels
nuclear fuel
37
what are the renewable energy sources
biofuel
wind
hydroelectricity
geothermal
tidal
solar
water waves
38
what is renewable energy
energy which can be replenished as it is used
39
what is non renewable energy
energy that has a finite supply that will run out
40
why is non renewable energy helpful for large scale energy supplies
large energy output per kilogram of fuel compared to renewable resources
41
why has renewable energy become more important
development has become more important due to fossil fuels finite lifetime
42
why is renewable energy not always reliable
solar doesn't work in bad weather or night
wind is only intermittent
43
what are the main energy uses
transport
electricity generation
heating
44
what is the environmental impacts from the extraction of energy
fossil fuels involve destroying landscapes
wind turbines can be considered an eyesore
45
what is the environmental impact of the use of energy sources
fossil fuels release harmful emissions
solar, wind directly create electricity with no emissions
46
when were fossil fuels most popular
industrial period - they were easy t0 mine and gave a lot of energy
47
when has renewable energy become more popular
modern times , technology developed to harness such energy sources efficiently
48
why is it easier to use energy resources
increasing pressure ti cope with power demands
49
why is it difficult to use energy resources
harder to solve environmenta issues due ti political social ethical and economic considerations
50
what is electrical energy
energy transfer due to an electrical current
51
why is electrical energy useful
it is easy to transfer into other more useful tupes of energy
52
what is total cost
no of kwh x cost of 1kwh
53
what is the efficiency equation
useful energy/ total energy in x100
54
what is efficiency
a measure of how good a device is at changing energy from one form to another
55
what can efficiency not be greater than
1
56
what is the power equation
energy / time
57
what is power
the amount of energy transferred by a device in one second
58
what does the gpe depend on
its mass and height above the earths surface
59
what is the law of conservation of energy
if an object falls, the gpe it loses must turn into a different form
60
what is a constant
value of something that never changes
61
how can heat travel
conduction
convection
radiation
62
what is the 2nd law of thermodynamics
heat always travels from regions of hot to regions of cold
63
how do conductors work (particle wise)
particles gain more energy, vibrate more vigorously and collide with their neighbours. the free electrons gain kinetic energy when a metal is heated.
64
what is thermal conductivity
the rate at which a material transfers heat energy
65
what does insulate mean
reduce the amount of energy transfers across a material
thermal insulation is to reduce the rate of heat energy transfer
66
what is specific heat capacity
the amount of energy needed to change the temperature of 1kg of a substance by 1 degree
67
what does the rate of energy transfer across a material depend on
temperature difference across the material
thickness of the material
thermal conductivity of the material
68
what properties should thermal insulation have
as low thermal conductivity as possible
be as thick as practically possible
69
what is payback time
how long it takes for the cost of installing insulation to be equalled by the savings from reduced energy costs
70
what is the payback time equation
payback time = cost to install/savings each year
71
what does the amount of energy needed to heat a substance depend on
mass of substance
substance itself
temperature change
72
what do all objects emit
radiation
73
what can detect radiation
a thermal camera
74
what comes up when we image infrared
shows up as a bright patch
75
what colours indicate a high level of infrared
yellow , oranges
76
what does amount of heat out equal
amount of heat in
77
what is thermal equilibrium
where the heat matches its surroundings
78
what is infrared radiation
a type of electromagnetic wave which transfers heat energy
79
how is the thermal heat emitted from objects
as infrared radiation
80
what are the best emitters of radiation
matte black
81
what is the best absorber of radiation
matte black
82
what are the worst emitters of radiation
silver shiny surfaces
83
what is the best reflector of radiation
silver shiny
84
what is a black body emitter
an object that absorbs all radiation that hits it and does not reflect any
85
how can an object stay at a constant temp (radiation)
a body that absorbs infrared radiation at the same rate as it emits it
(thermal equilibrium)
86
what does a black body not do
reflect radiation
87
what happens to the temperature when the rate of absorption is the greater than the rate of emission
increases
88
what happens to the temperature when the rate of absorption is equal to the rate of emissio
constant
89
what happens to the temperature when the rate of absorption is less than the rate of emission
decrease
90
what is biofuel
fuel taken away from living or recently living organisms
91
why are biofuels renewable
can be grown or continually produced
92
how are biofuels carbon neutral
they take in the same amount of carbon they release when burnt
93
how does nuclear power work
nuclear fuel uses the energy released from unstable atoms when they split (nuclear fission)
94
how does nuclear fuel release heat energy
the energy from the nuclear material in the core releases a lot of heat energy which is transferred to a fluid which is pumped through the core
95
what are the advantages of nuclear fuel
reliable generation of electricity
no co2 or SO2 produced
96
how much energy does nuclear power use
300,000 MJ
97
what kind of fuel does nuclear power use
uranium, plutonium
98
what waste products does nuclear power release
radioactive fuel rods
99
what does nuclear power emit into the atmosphere
none
100
what fuels are used in fossil fuels
coal, oil, gas
101
how much energy is used for fossil fuel power
30MJ
102
what are the waste products of fossil fuel power
ash
103
what does using fossil fuel power emit into the atmosphere
co2 - greenhouse gas
so2 - acid rain
104
what does carbon neutral mean
net carbon is 0
105
what does recyclable mean
can be made into something else
106
how does hydroelectric power work
a dam is built, water is stored and allowed to flow town, turning a turbine
turbine is connected to a generator
107
what are the advantages of hydroelectric power
no co2 released because no fuel is burnt
renewable
we can store water up high and whenever we need the energy we can let the water out
108
what are the disadvantages of hydroelectric power
costs a lot of money to build a dam
dam can ruin the local environment as it changes where water naturally flows
some animals and plants could die
109
how does tidal energy work
dam is built across a river estuary
water flows in and out of the estuary through turbines in the dam which harness the tidal energy
110
what are the advantages of tidal energy
renewable
no co2 produced because fuel isn't burnt
reliable, two tides everyday
cheap to run once its built
111
what are the disadvantages of tidal energy
costs a lot to build the dam
the dam may cause local flooding
112
how does solar energy work
solar cells turn light energy from the sun directly into current electricity
113
what are the advantages of solar energy
renewable
no co2 produced because no fuel is burnt
114
what are the disadvantages of solar energy
solar cells and solar panels are expensive
only works if it's sunny
115
how does geothermal energy work
radioactive decay of uranium releases heat energy that warms the rocks
116
what are the advantages of geothermal energy
renewable
no co2 produced because no fuel is burnt
doesn't damage the environment
117
what are the disadvantages of geothermal energy
very few places in the world where you can do it
costs a lot of money to drill deep into the ground
118
how does biomass energy work
anything that is grown
it can be burned instead of fossil fuels
119
what are the advantages of biofuel
renewable as long as we keep planting trees to replace the ones we cut down
doesn't need any special equipment so it can be used very easily, even in poor countries
120
what are the disadvantages of biomass energy
large areas of land are needed to grow enough trees
121
how does wave energy work
kinetic energy from the seas waves is turned into electrical energy to be used in homes
122
what are the advantages of wave energy
renewable
no co2 produced because no fuel is burnt
123
what are the disadvantages of wave energy
needs a lot of machines to get a reasonable amount of energy
the machines cost a lot of money / can be ugly / can be damaged
124
how does wind energy work
kinetic energy of the wind turns the turbine blades
the moving blades turn a generator which generates electricity
125
what are the advantages of wind energy
no co2 produced because no fuel is burnt
turbines are quite cheap and easy to build so they can be used even in poor countries
126
what are the disadvantages of wind energy
turbines can be ugly and noisy
only work if its quite windy
if the wind stops , you get no energy
127
what does burning fossil fuels create
carbon dioxide - greenhouse gas (contributes to global warming
sulphur dioxide - acid rain
ash - needs disposed of in a land fill
128
what is global warming
the whole earth heating up due to the gases emitted into the atmosphere making it warmer and trapping the suns heat
129
what problems does the temperature increase of the earth cause
extreme weather, sea levels rising, drought
130
how does carbon capture storage work
oil and gas fields are used to store carbon dioxide
process of capturing waste carbon dioxide
131
which energy type has the longest start up time
nuclear
132
what is nuclear energy good for
supplying basic (base load) demand
get a lot of energy per kg of fuel
133
which energy has the shortes start up time
natural gas
134
what is natural gas good for
meets extra demands daily and at different times of year
135
how can we meet energy demand
a pumped storage scheme
renewable resources when demand is high and weather conditions are suitable
renewable resources when demand is low to store energy in pumped storage schemes
