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Physics > Energy > Flashcards

Energy Flashcards

1
Q

is energy ever used up ?

A

no, just transferred between different energy stores and different objects

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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

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3
Q

how is energy transferred?

A

mechanically (doing work)
electrically (work done by moving charges)
heating
radiation

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4
Q

what happens when a system changes?

A

energy is transferred

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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

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6
Q

what is work done?

A

energy transferred

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7
Q

when can work be done?

A

when current flows
a force moving an object

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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

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9
Q

what happens to a falling object with air resistance?

A

energy is transferred to other stores of the object and surroundings

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10
Q

kinetic energy equation

A

kinetic energy = 1/2 x m x v^2

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11
Q

gravitational potential energy equation

A

gpe= m x g x h

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12
Q

elastic potential energy equation

A

elastic potential = 1/2 x spring constant x extension^2

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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

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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

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15
Q

specific heat capacity equation

A

change in energy = mass x specific heat capacity x temp change

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16
Q

what is the law of conservation of energy

A

energy can be transferred, stored or dissipated but never created or destroyed

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17
Q

what is power

A

the rate at which energy is transferred or the rate at which work is done

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18
Q

power equation

A

power = energy transferred / time

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19
Q

what is a watt

A

1 joule of energy transferred per second

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20
Q

how does lubrication reduce energy waste

A

oil in a motor
reduces friction
less energy is lost as heat through friction

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21
Q

how does thermal insulation reduce energy waste

A

double glazing
less useful thermal energy is lost

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22
Q

what is conduction

A

the process where vibrating particles transfer energy to neighbouring particles

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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

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24
Q

what would happen to heat in a building with thin metal walls

A

lost very quickly

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25
Q

what would happen to heat in a building with thick walls

A

rate of cooling is low
thermal conductivity low

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26
Q

what is convection

A

when energetic particles move away from hotter to cooler regions

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27
Q

where can convection happen

A

gases and liquids

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28
Q

how do radiators heat a room

A

create convection currents in the air of the room

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29
Q

what is the difference between convection and conduction

A

convection particles move by taking their energy with them
conduction vibrating particles transfer energy to other particles

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30
Q

what are the two ways to reduce unwanted energy transfers

A

lubrication
thermal insulation

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31
Q

how does lubrication avoid wasting energy

A

reduces frictional forces

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32
Q

how does insulation reduce unwanted energy transfers

A

heating

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33
Q

what are the examples of thermal insulation in houses

A

cavity walls (air gap or foam)
loft insulation (fibreglass wool)
double glazed windows
draught excluders (around doors and windows to avoid convection)

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34
Q

efficiency equation

A

efficiency = useful energy output/ total energy input

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35
Q

how can efficiency of a system be increased

A

reducing waste output (lubrication, thermal insulation)
recycling waste output ( absorbing thermal waste and recycling as input energy)

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36
Q

what are the non renewable energy sources

A

fossil fuels
nuclear fuel

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37
Q

what are the renewable energy sources

A

biofuel
wind
hydroelectricity
geothermal
tidal
solar
water waves

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38
Q

what is renewable energy

A

energy which can be replenished as it is used

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39
Q

what is non renewable energy

A

energy that has a finite supply that will run out

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40
Q

why is non renewable energy helpful for large scale energy supplies

A

large energy output per kilogram of fuel compared to renewable resources

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41
Q

why has renewable energy become more important

A

development has become more important due to fossil fuels finite lifetime

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42
Q

why is renewable energy not always reliable

A

solar doesn’t work in bad weather or night
wind is only intermittent

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43
Q

what are the main energy uses

A

transport
electricity generation
heating

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44
Q

what is the environmental impacts from the extraction of energy

A

fossil fuels involve destroying landscapes
wind turbines can be considered an eyesore

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45
Q

what is the environmental impact of the use of energy sources

A

fossil fuels release harmful emissions
solar, wind directly create electricity with no emissions

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46
Q

when were fossil fuels most popular

A

industrial period - they were easy t0 mine and gave a lot of energy

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47
Q

when has renewable energy become more popular

A

modern times , technology developed to harness such energy sources efficiently

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48
Q

why is it easier to use energy resources

A

increasing pressure ti cope with power demands

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49
Q

why is it difficult to use energy resources

A

harder to solve environmenta issues due ti political social ethical and economic considerations

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50
Q

what is electrical energy

A

energy transfer due to an electrical current

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51
Q

why is electrical energy useful

A

it is easy to transfer into other more useful tupes of energy

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52
Q

what is total cost

A

no of kwh x cost of 1kwh

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53
Q

what is the efficiency equation

A

useful energy/ total energy in x100

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54
Q

what is efficiency

A

a measure of how good a device is at changing energy from one form to another

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55
Q

what can efficiency not be greater than

A

1

56
Q

what is the power equation

A

energy / time

57
Q

what is power

A

the amount of energy transferred by a device in one second

58
Q

what does the gpe depend on

A

its mass and height above the earths surface

59
Q

what is the law of conservation of energy

A

if an object falls, the gpe it loses must turn into a different form

60
Q

what is a constant

A

value of something that never changes

61
Q

how can heat travel

A

conduction
convection
radiation

62
Q

what is the 2nd law of thermodynamics

A

heat always travels from regions of hot to regions of cold

63
Q

how do conductors work (particle wise)

A

particles gain more energy, vibrate more vigorously and collide with their neighbours. the free electrons gain kinetic energy when a metal is heated.

64
Q

what is thermal conductivity

A

the rate at which a material transfers heat energy

65
Q

what does insulate mean

A

reduce the amount of energy transfers across a material
thermal insulation is to reduce the rate of heat energy transfer

66
Q

what is specific heat capacity

A

the amount of energy needed to change the temperature of 1kg of a substance by 1 degree

67
Q

what does the rate of energy transfer across a material depend on

A

temperature difference across the material
thickness of the material
thermal conductivity of the material

68
Q

what properties should thermal insulation have

A

as low thermal conductivity as possible
be as thick as practically possible

69
Q

what is payback time

A

how long it takes for the cost of installing insulation to be equalled by the savings from reduced energy costs

70
Q

what is the payback time equation

A

payback time = cost to install/savings each year

71
Q

what does the amount of energy needed to heat a substance depend on

A

mass of substance
substance itself
temperature change

72
Q

what do all objects emit

A

radiation

73
Q

what can detect radiation

A

a thermal camera

74
Q

what comes up when we image infrared

A

shows up as a bright patch

75
Q

what colours indicate a high level of infrared

A

yellow , oranges

76
Q

what does amount of heat out equal

A

amount of heat in

77
Q

what is thermal equilibrium

A

where the heat matches its surroundings

78
Q

what is infrared radiation

A

a type of electromagnetic wave which transfers heat energy

79
Q

how is the thermal heat emitted from objects

A

as infrared radiation

80
Q

what are the best emitters of radiation

A

matte black

81
Q

what is the best absorber of radiation

A

matte black

82
Q

what are the worst emitters of radiation

A

silver shiny surfaces

83
Q

what is the best reflector of radiation

A

silver shiny

84
Q

what is a black body emitter

A

an object that absorbs all radiation that hits it and does not reflect any

85
Q

how can an object stay at a constant temp (radiation)

A

a body that absorbs infrared radiation at the same rate as it emits it
(thermal equilibrium)

86
Q

what does a black body not do

A

reflect radiation

87
Q

what happens to the temperature when the rate of absorption is the greater than the rate of emission

A

increases

88
Q

what happens to the temperature when the rate of absorption is equal to the rate of emissio

A

constant

89
Q

what happens to the temperature when the rate of absorption is less than the rate of emission

A

decrease

90
Q

what is biofuel

A

fuel taken away from living or recently living organisms

91
Q

why are biofuels renewable

A

can be grown or continually produced

92
Q

how are biofuels carbon neutral

A

they take in the same amount of carbon they release when burnt

93
Q

how does nuclear power work

A

nuclear fuel uses the energy released from unstable atoms when they split (nuclear fission)

94
Q

how does nuclear fuel release heat energy

A

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
Q

what are the advantages of nuclear fuel

A

reliable generation of electricity
no co2 or SO2 produced

96
Q

how much energy does nuclear power use

A

300,000 MJ

97
Q

what kind of fuel does nuclear power use

A

uranium, plutonium

98
Q

what waste products does nuclear power release

A

radioactive fuel rods

99
Q

what does nuclear power emit into the atmosphere

A

none

100
Q

what fuels are used in fossil fuels

A

coal, oil, gas

101
Q

how much energy is used for fossil fuel power

A

30MJ

102
Q

what are the waste products of fossil fuel power

A

ash

103
Q

what does using fossil fuel power emit into the atmosphere

A

co2 - greenhouse gas
so2 - acid rain

104
Q

what does carbon neutral mean

A

net carbon is 0

105
Q

what does recyclable mean

A

can be made into something else

106
Q

how does hydroelectric power work

A

a dam is built, water is stored and allowed to flow town, turning a turbine
turbine is connected to a generator

107
Q

what are the advantages of hydroelectric power

A

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
Q

what are the disadvantages of hydroelectric power

A

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
Q

how does tidal energy work

A

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
Q

what are the advantages of tidal energy

A

renewable
no co2 produced because fuel isn’t burnt
reliable, two tides everyday
cheap to run once its built

111
Q

what are the disadvantages of tidal energy

A

costs a lot to build the dam
the dam may cause local flooding

112
Q

how does solar energy work

A

solar cells turn light energy from the sun directly into current electricity

113
Q

what are the advantages of solar energy

A

renewable
no co2 produced because no fuel is burnt

114
Q

what are the disadvantages of solar energy

A

solar cells and solar panels are expensive
only works if it’s sunny

115
Q

how does geothermal energy work

A

radioactive decay of uranium releases heat energy that warms the rocks

116
Q

what are the advantages of geothermal energy

A

renewable
no co2 produced because no fuel is burnt
doesn’t damage the environment

117
Q

what are the disadvantages of geothermal energy

A

very few places in the world where you can do it
costs a lot of money to drill deep into the ground

118
Q

how does biomass energy work

A

anything that is grown
it can be burned instead of fossil fuels

119
Q

what are the advantages of biofuel

A

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
Q

what are the disadvantages of biomass energy

A

large areas of land are needed to grow enough trees

121
Q

how does wave energy work

A

kinetic energy from the seas waves is turned into electrical energy to be used in homes

122
Q

what are the advantages of wave energy

A

renewable
no co2 produced because no fuel is burnt

123
Q

what are the disadvantages of wave energy

A

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
Q

how does wind energy work

A

kinetic energy of the wind turns the turbine blades
the moving blades turn a generator which generates electricity

125
Q

what are the advantages of wind energy

A

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
Q

what are the disadvantages of wind energy

A

turbines can be ugly and noisy
only work if its quite windy
if the wind stops , you get no energy

127
Q

what does burning fossil fuels create

A

carbon dioxide - greenhouse gas (contributes to global warming
sulphur dioxide - acid rain
ash - needs disposed of in a land fill

128
Q

what is global warming

A

the whole earth heating up due to the gases emitted into the atmosphere making it warmer and trapping the suns heat

129
Q

what problems does the temperature increase of the earth cause

A

extreme weather, sea levels rising, drought

130
Q

how does carbon capture storage work

A

oil and gas fields are used to store carbon dioxide
process of capturing waste carbon dioxide

131
Q

which energy type has the longest start up time

A

nuclear

132
Q

what is nuclear energy good for

A

supplying basic (base load) demand
get a lot of energy per kg of fuel

133
Q

which energy has the shortes start up time

A

natural gas

134
Q

what is natural gas good for

A

meets extra demands daily and at different times of year

135
Q

how can we meet energy demand

A

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

Physics (17 decks)

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