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Physics > Energy > Flashcards

Energy Flashcards

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1
Q

Energy stores

A
  • magnetic
  • electrostatic
  • nuclear
  • gravitational potential
  • elastic potential
  • thermal
  • chemical potential
  • kinetic
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2
Q

Energy transfer pathways

A
  • mechanical
  • electricity
  • heating
  • radiation
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3
Q

Mechanical energy transfer

A

Energy transferred by a force doing work

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4
Q

Electrical energy transfer

A

Energy transferred through work done by moving charges

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5
Q

System

A

An object or group of objects

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6
Q

What happens when a system changes

A
  • energy transferred into or away from the system
    OR
  • energy transferred between objects in a system
    OR
  • energy transferred between different types of energy stores
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7
Q

Closed system

A
  • system where neither matter nor energy can enter or leave
  • net change in total energy always 0
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8
Q

Work done

A

Energy transferred

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9
Q

What causes energy to be transferred to kinetic store

A

Object speeding up

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10
Q

Kinetic energy formula

A

Eₖ = 0.5 x M x V²

M = mass
V = speed

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11
Q

What causes energy to be transferred to GPE store

A

Lifting an object higher in a gravitational field

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12
Q

Where does energy lost from GPE store go with no air resistance

A

Kinetic energy store

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13
Q

GPE formula

A

Eₚ = mgh

m - mass
g - gravitational field strength
h - height

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14
Q

What causes energy to be transferred to elastic potential store

A

Stretching or squashing an object if the limit of proportionality hasn’t been exceeded

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15
Q

Specific heat capacity

A

The amount of energy needed to raise the temperature of 1kg of a substance by 1°C

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16
Q

Specific heat capacity practical

A
  • measure mass of solid block
  • wrap block in insulating layer
  • insert thermometer and heater into block’s 2 holes
  • measure temp of block
  • set p.d to 10V
  • turn on power supply, start watch
  • circuit’s current does work on heater, transferring electrical energy to thermal store, transferred to object to heat it
  • take temp/current readings every minute for 10 minutes
  • turn off power supply
  • calculate power supplied to heater, energy transferred to heater
  • plot graph of energy transferred to temperature
  • find specific heat capacity - 1 ÷ (gradient x block’s mass)
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17
Q

Law of conservation of energy

A

Energy can’t be created or destroyed, only transferred between stores

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18
Q

Dissipation

A

Energy lost in a reaction by being transferred to thermal stores

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19
Q

Power

A

Rate of doing work

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20
Q

Unit of power

A

Watt (W)

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21
Q

What is a watt

A

1 joule of energy transferred per second

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22
Q

Power formula

A

P = E / T

E - energy transferred
T - time

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23
Q

How to reduce unwanted energy transfers

A
  • lubrication
  • insulation
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24
Q

How does lubrication reduce unwanted energy transfers

A

Reduces frictional forces

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25
Q

How does lubrication reduce frictional forces

A

Liquids/oils that flow easily between objects stop objects rubbing together

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26
Q

How does insulation prevent unwanted energy transfers

A

Thick walls and low thermal conductivity reduce rate of energy transfer by heating

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27
Q

Conduction

A
  • when object heated, energy transferred to kinetic store of particles
  • particles vibrate and collide with each other
  • collisions cause kinetic energy transfer between particles (conduction)
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28
Q

Convection

A

Method of energy transfer in liquids/gases where energetic particles move from hotter to cooler regions

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29
Q

Efficiency of energy transfer formula

A

Useful output energy transfer / Total input energy transfer

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30
Q

Efficiency from power formula

A

Useful power output / Total power input

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31
Q

Efficiency

A

How good a device is at transferring useful energy from one store to another

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32
Q

Where do wasted energy transfers usually go

A

Thermal energy stores

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33
Q

100% efficient device

A

Electric heater

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34
Q

Why are electric heaters 100% efficient

A

All electrostatic energy store energy is transferred to useful thermal stores

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35
Q

Where is all energy eventually transferred

A

Thermal stores

36
Q

Types of energy resources

A
  • renewable
  • non-renewable
37
Q

What are renewable energy resources

A
  • will never run out
  • can be replenished
  • do less damage to environment than non-renewables
  • don’t provide as much energy
  • unreliable
38
Q

Renewable energy resources

A
  • solar
  • wind
  • water waves
  • hydro-electricity
  • bio-fuel
  • tides
  • geothermal
39
Q

What are non-renewable energy resources

A
  • fossil and nuclear fuels
  • will eventually run out
  • damage environment
  • provide most of our energy
40
Q

Non-renewable energy resources

A
  • coal
  • oil
  • natural gas
41
Q

Fossil fuels

A
  • natural resources that form underground over millions of years
  • typically burnt to provide energy
42
Q

Nuclear fuels

A
  • uranium
  • plutonium
43
Q

Define reliable in terms of energy resources

A

Resources that can be relied on to supply in a predictable way when needed

44
Q

Units for specific heat capacity

A

J/kg°C

45
Q

Uses of energy resources

A
  • generating electricity
  • transport
  • heating
46
Q

Where are renewable energy resources used in transport

A

Some vehicles run on purely bio-fuels or mix of petrol and bio-fuels

47
Q

Where are non-renewable energy resources used in transport

A
  • petrol/diesel cars use fuel from oil
  • coal used in some old fashioned trains to boil water to generate steam
48
Q

Where are renewable energy resources used in heating

A
  • geothermal heat pumps
  • solar water heaters - use sun to heat water which is pumped into radiators
  • burning biofuel
49
Q

Factors considered when choosing energy resource

A
  • environmental
  • political
  • social
  • economic
50
Q

Best places for wind turbines

A

Exposed places
- moors
- coasts

51
Q

How do wind turbines work

A
  • each turbine has generator
  • wind rotates blades which turn generator to produce electricity
52
Q

Advantages of wind turbines

A
  • no pollution
  • no fuel costs
  • minimal running costs
  • no permanent damage to landscape
53
Q

Disadvantages of wind turbines

A
  • spoil view
  • noisy
  • stopping when wind stops
  • high initial costs
  • can’t increase power output when high demand
54
Q

How so solar cells work

A

Generate electric currents directly from sunlight

55
Q

Advantages of solar cells

A
  • no pollution
  • very reliable in sunny countries
  • almost no running costs
56
Q

Disadvantages of solar cells

A
  • only reliable in daytime
  • can’t increase power output when extra demand
  • high initial costs
57
Q

Geothermal power

A
  • energy taken from underground thermal stores in volcanic areas / areas with hot rocks near surface
  • energy is slow decay of radioactive elements inside Earth
58
Q

Advantages of geothermal power

A
  • free energy
  • reliable
  • little damage to environment
59
Q

Disadvantages of geothermal power

A
  • not many suitable locations
  • high cost to build plant
60
Q

Hydro-electric power

A

Generates electricity through water falling through turbines - usually requires flooding of valley by building dam

61
Q

Advantages of hydro-electric power

A
  • no pollution
  • provide immediate response to increased demand
  • reliable unless drought
  • no fuel costs
  • minimal running costs
62
Q

Disadvantages of hydro-electric power

A
  • impacts on environment by flooding valley - rotting vegetation releases methane + CO₂
  • loss of habitat for some species
  • high initial costs
63
Q

Wave power

A
  • many small wave powered turbines around coast
  • turbines connect to generator to generate electricity when moving
64
Q

Advantages of wave-power

A
  • no pollution
  • no fuel costs
  • minimal running costs
65
Q

Disadvantages of wave-power

A
  • disturbing seabed + habits of marine animals
  • spoiling view
  • hazardous to boats
  • unreliable - waves die went wind drops
  • high initial costs
66
Q

Tidal barrages

A

Big dams built across river estuaries containing turbines, as tide (produced by gravitational pull of sun and moon) comes in, water moves through turbines which generate electricity

67
Q

Advantages of tidal barrages

A
  • no pollution
  • mostly reliable - always 2 tides a day
  • no fuel costs
  • minimal running costs
68
Q

Disadvantages of tidal barrages

A
  • prevent free access of boats
  • spoil view
  • alter habitat of wildlife
  • somewhat unreliable - size of tides vary
  • high initial costs
69
Q

Bio-fuels

A

Plant products or animal dung burnt to produce energy or run cars

70
Q

Advantages of bio-fuels

A
  • carbon neutral if plants grown at same rate as being burned
  • mostly reliable - crops take short time to grow
71
Q

Disadvantages of bio-fuels

A
  • can’t respond to immediate demand - bio-fuels produced and stored for when needed to combat this
  • high cost to refine
  • may not be enough space/water to grow plants
  • clearing room to grow them can result in loss of habitat
  • decay of burning the vegetation increases CO₂ + methane emissions
72
Q

Why are nuclear and fossil fuels reliable

A

There’s enough to meet current demand, extracted from Earth at fast enough rate that power plants always have fuel so can respond quickly if demand changes

73
Q

Advantages of a power plant

A
  • cheaper running costs
  • low fuel extraction costs
  • cost effective
74
Q

Disadvantages of power plants

A
  • high set-up cost
  • environmental problems
75
Q

Environmental problems caused by non-renewables

A
  • burning coal/oil/gas releases CO₂
  • burning coal/oil/gas release of sulfur dioxide - causes acid rain
  • coal mining can spoil view
  • oil spillages
  • nuclear waste is dangerous + difficult to dispose of
  • nuclear power can cause major catastrophes
76
Q

Effects of acid rain

A
  • harm to trees/soils
  • harmful to ecosystems
77
Q

How to reduce acid rain

A
  • take out sulfur before burning fuel
  • clean up emissions
78
Q

Effect of oil spillages

A

Affects mammals/birds living around sea

79
Q

What has happened to use of electricity in UK

A

It has slowly decreased since the beginning of the 21st century

80
Q

Why has electricity usage slowly decreased since the start of the 21st century

A

Appliances have become more efficient

81
Q

Reasons for burning fossil fuels

A
  • electricity generation
  • fueling cars with oil
  • heating homes + cooking with gas
82
Q

Why do people want to use more renewable energy

A

To protect the environment

83
Q

What limits use of renewables

A
  • reliability
  • money
  • politics
84
Q

How does money limit use of renewables

A
  • cost of non-renewable power plants must be paid for by customer bills or government taxes
  • hybrid cards are expensive
  • solar panels are expensive
  • research costs into renewables are expensive
85
Q

How does politics limit use of renewables

A
  • arguments over where to put new power plants
  • e.g- people may think’s it’s unethical to make people live next to a wind farm

Physics (4 decks)

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