Energy Flashcards
(94 cards)
1
Q
Energy stores
A
- magnetic
- electrostatic
- nuclear
- gravitational potential
- elastic potential
- thermal
- chemical potential
- kinetic
2
Q
Energy transfer pathways
A
- mechanical
- electricity
- heating
- radiation
3
Q
Mechanical energy transfer
A
Energy transferred by a force doing work
4
Q
Electrical energy transfer
A
Energy transferred through work done by moving charges
5
Q
System
A
An object or group of objects
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
7
Q
Closed system
A
- system where neither matter nor energy can enter or leave
- net change in total energy always 0
8
Q
Work done
A
Energy transferred
9
Q
What causes energy to be transferred to kinetic store
A
Object speeding up
10
Q
What causes energy to be transferred to GPE store
A
Lifting an object higher in a gravitational field
11
Q
Where does energy lost from GPE store go with no air resistance
A
Kinetic energy store
12
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
13
Q
When can elastic potential energy equation be used
A
When limit of proportionality has not been exceeded
14
Q
Limit of proportionality
A
Maximum force, above which extension is no longer proportional to force (graph will curve upwards)
15
Q
Units of spring constant
A
N/m
16
Q
Specific heat capacity
A
The amount of energy needed to raise the temperature of 1kg of a substance by 1°C
17
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)
18
Q
Unit of specific heat capacity
A
J/kg °C
19
Q
Law of conservation of energy
A
Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed
20
Q
Dissipation
A
Energy lost in a reaction by being transferred to thermal stores
21
Q
Power
A
Rate of doing work
22
Q
Unit of power
A
Watt (W)
23
Q
What is a watt
A
1 joule of energy transferred per second
24
Q
Gravitational field strength
A
9.8 N/kg
25
Methods of reducing unwanted energy transfers
- lubrication
- insulation
26
How does lubrication reduce unwanted energy transfers
Reduces frictional forces
27
How does lubrication reduce frictional forces
Liquids/oils that flow easily between objects stop objects rubbing together
28
How does insulation prevent unwanted energy transfers
Thick walls and low thermal conductivity reduce rate of energy transfer by heating
29
How does thermal conductivity affect rate of energy tranfer
Higher thermal conductivity of material means higher rate of energy transfer by conduction across material
30
Examples of thermal insulation
- cavity walls
- loft insulation
- double-glazed windows
- daught excluders
31
Cavity walls
- inner outer wall with air gap in middle
- air gap reduced energy transferred by conduction through walls
- sometimes gap filled with foam to reduce convection
32
Loft insulation
Reduce convection currents within lofts
33
Convection currents
Cycle where air particles are constantly being heating, rising, cooling, sinking
34
Double glazed windows
- air gap between 2 sheets of glass
- prevent energy transfer by conduction through windows
35
Draught excluders
Put around windows and doors to reduce energy transfers by convection
36
How does temperature outside compared to inside affect rate of energy transfer
Greater difference between inside/outside reduces rate of energy transfer
37
Conduction
- 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)
38
Convection
Method of energy transfer in liquids/gases where energetic particles move from hotter to cooler regions
39
Efficiency
How good a device is at transferring useful energy from one store to another
40
Where do wasted energy transfers usually go
Thermal energy stores
41
100% efficient device
Electric heater
42
Why are electric heaters 100% efficient
All electrostatic energy store energy is transferred to useful thermal stores
43
Where is all energy eventually transferred
Thermal stores
44
Types of energy resources
- renewable
- non-renewable
45
Features of renewable energy resources
- will never run out
- can be replenished
- do less damage to environment than non-renewables
- don’t provide as much energy
- unreliable
46
What are the renewable energy resources
- solar
- wind
- water waves
- hydro-electricity
- bio-fuel
- tides
- geothermal
47
Features of non-renewable energy resources
- fossil and nuclear fuels
- will eventually run out
- damage environment
- provide most of our energy
48
Non-renewable energy resources
- coal
- oil
- natural gas
49
Fossil fuels
- natural resources that form underground over millions of years
- typically burnt to provide energy
50
Nuclear fuels
- uranium
- plutonium
51
Define reliable in terms of energy resources
Resources that can be relied on to supply in a predictable way when needed
52
Units for specific heat capacity
J/kg°C
53
Uses of energy resources
- generating electricity
- transport
- heating
54
Where are renewable energy resources used in transport
Some vehicles run on purely bio-fuels or mix of petrol and bio-fuels
55
Where are non-renewable energy resources used in transport
- petrol/diesel cars use fuel from oil
- coal used in some old fashioned trains to boil water to generate steam
56
Where are renewable energy resources used in heating
- geothermal heat pumps
- solar water heaters - use sun to heat water which is pumped into radiators
57
Factors considered when choosing energy resource
- environmental
- political
- social
- economic
58
Best places for wind turbines
Exposed places
- moors
- coasts
59
How do wind turbines work
- each turbine has generator
- wind rotates blades which turn generator to produce electricity
60
Advantages of wind turbines
- no pollution
- no fuel costs
- minimal running costs
- no permanent damage to landscape
61
Disadvantages of wind turbines
- spoil view
- noisy
- stopping when wind stops
- high initial costs
- can’t increase power output when high demand
62
How so solar cells work
Generate electric currents directly from sunlight
63
Advantages of solar cells
- no pollution
- very reliable in sunny countries
- almost no running costs
64
Disadvantages of solar cells
- only reliable in daytime
- can’t increase power output when extra demand
- high initial costs
65
Geothermal power
- energy taken from underground thermal stores in volcanic areas / areas with hot rocks near surface
- energy is slow decay of radioactive elements inside Earth
66
Advantages of geothermal power
- free energy
- reliable
- little damage to environment
67
Disadvantages of geothermal power
- not many suitable locations
- high cost to build plant
68
Hydro-electric power
Generates electricity through water falling through turbines - usually requires flooding of valley by building dam
69
Advantages of hydro-electric power
- no pollution
- provide immediate response to increased demand
- reliable unless drought
- no fuel costs
- minimal running costs
70
Disadvantages of hydro-electric power
- impacts on environment by flooding valley - rotting vegetation releases methane + CO₂
- loss of habitat for some species
- high initial costs
71
Wave power
- many small wave powered turbines around coast
- turbines connect to generator to generate electricity when moving
72
Advantages of wave-power
- no pollution
- no fuel costs
- minimal running costs
73
Disadvantages of wave-power
- disturbing seabed + habits of marine animals
- spoiling view
- hazardous to boats
- unreliable - waves die went wind drops
- high initial costs
74
Tidal barrages
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
75
Advantages of tidal barrages
- no pollution
- mostly reliable - always 2 tides a day
- no fuel costs
- minimal running costs
76
Disadvantages of tidal barrages
- prevent free access of boats
- spoil view
- alter habitat of wildlife
- somewhat unreliable - size of tides vary
- high initial costs
77
Bio-fuels
Plant products or animal dung burnt to produce energy or run cars
78
Advantages of bio-fuels
- carbon neutral if plants grown at same rate as being burned
- mostly reliable - crops take short time to grow
79
Disadvantages of bio-fuels
- 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
80
Why are nuclear and fossil fuels reliable
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
81
Advantages of a power plant
- cheaper running costs
- low fuel extraction costs
- cost effective
82
Disadvantages of power plants
- high set-up cost
- environmental problems
83
Environmental problems caused by non-renewables
- 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
84
Effects of acid rain
- harm to trees/soils
- harmful to ecosystems
- corrosion of buildings/structures
85
How to reduce acid rain
- take out sulfur before burning fuel
- clean up emissions
86
Effect of oil spillages
Affects mammals/birds living around sea
87
What has happened to use of electricity in UK
- hugely increased over 20th century
- slowly decreased since the beginning of the 21st century
88
Why did electricity use massively increases over 20th century
- population grew
- people used electricity for more and more things
89
Why has electricity usage slowly decreased since the start of the 21st century
Appliances have become more efficient
90
Reasons for burning fossil fuels
- electricity generation
- fueling cars with oil
- heating homes + cooking with gas
91
Why do people want to use more renewable energy
To protect the environment
92
What limits use of renewables
- reliability
- money
- politics
93
How does money limit use of renewables
- 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
94
How does politics limit use of renewables
- 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
