Energy Flashcards
Energy stores
- magnetic
- electrostatic
- nuclear
- gravitational potential
- elastic potential
- thermal
- chemical potential
- kinetic
Energy transfer pathways
- mechanical
- electricity
- heating
- radiation
Mechanical energy transfer
Energy transferred by a force doing work
Electrical energy transfer
Energy transferred through work done by moving charges
System
An object or group of objects
What happens when a system changes
- 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
Closed system
- system where neither matter nor energy can enter or leave
- net change in total energy always 0
Work done
Energy transferred
What causes energy to be transferred to kinetic store
Object speeding up
Kinetic energy formula
Eₖ = 0.5 x M x V²
M = mass
V = speed
What causes energy to be transferred to GPE store
Lifting an object higher in a gravitational field
Where does energy lost from GPE store go with no air resistance
Kinetic energy store
GPE formula
Eₚ = mgh
m - mass
g - gravitational field strength
h - height
What causes energy to be transferred to elastic potential store
Stretching or squashing an object if the limit of proportionality hasn’t been exceeded
Specific heat capacity
The amount of energy needed to raise the temperature of 1kg of a substance by 1°C
Specific heat capacity practical
- 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)
Law of conservation of energy
Energy can’t be created or destroyed, only transferred between stores
Dissipation
Energy lost in a reaction by being transferred to thermal stores
Power
Rate of doing work
Unit of power
Watt (W)
What is a watt
1 joule of energy transferred per second
Power formula
P = E / T
E - energy transferred
T - time
How to reduce unwanted energy transfers
- lubrication
- insulation
How does lubrication reduce unwanted energy transfers
Reduces frictional forces
How does lubrication reduce frictional forces
Liquids/oils that flow easily between objects stop objects rubbing together
How does insulation prevent unwanted energy transfers
Thick walls and low thermal conductivity reduce rate of energy transfer by heating
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)
Convection
Method of energy transfer in liquids/gases where energetic particles move from hotter to cooler regions
Efficiency of energy transfer formula
Useful output energy transfer / Total input energy transfer
Efficiency from power formula
Useful power output / Total power input
Efficiency
How good a device is at transferring useful energy from one store to another
Where do wasted energy transfers usually go
Thermal energy stores
100% efficient device
Electric heater
Why are electric heaters 100% efficient
All electrostatic energy store energy is transferred to useful thermal stores
Where is all energy eventually transferred
Thermal stores
Types of energy resources
- renewable
- non-renewable
What are 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
Renewable energy resources
- solar
- wind
- water waves
- hydro-electricity
- bio-fuel
- tides
- geothermal
What are non-renewable energy resources
- fossil and nuclear fuels
- will eventually run out
- damage environment
- provide most of our energy
Non-renewable energy resources
- coal
- oil
- natural gas
Fossil fuels
- natural resources that form underground over millions of years
- typically burnt to provide energy
Nuclear fuels
- uranium
- plutonium
Define reliable in terms of energy resources
Resources that can be relied on to supply in a predictable way when needed
Units for specific heat capacity
J/kg°C
Uses of energy resources
- generating electricity
- transport
- heating
Where are renewable energy resources used in transport
Some vehicles run on purely bio-fuels or mix of petrol and bio-fuels
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
Where are renewable energy resources used in heating
- geothermal heat pumps
- solar water heaters - use sun to heat water which is pumped into radiators
Factors considered when choosing energy resource
- environmental
- political
- social
- economic
Best places for wind turbines
Exposed places
- moors
- coasts
How do wind turbines work
- each turbine has generator
- wind rotates blades which turn generator to produce electricity
Advantages of wind turbines
- no pollution
- no fuel costs
- minimal running costs
- no permanent damage to landscape
Disadvantages of wind turbines
- spoil view
- noisy
- stopping when wind stops
- high initial costs
- can’t increase power output when high demand
How so solar cells work
Generate electric currents directly from sunlight
Advantages of solar cells
- no pollution
- very reliable in sunny countries
- almost no running costs
Disadvantages of solar cells
- only reliable in daytime
- can’t increase power output when extra demand
- high initial costs
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
Advantages of geothermal power
- free energy
- reliable
- little damage to environment
Disadvantages of geothermal power
- not many suitable locations
- high cost to build plant
Hydro-electric power
Generates electricity through water falling through turbines - usually requires flooding of valley by building dam
Advantages of hydro-electric power
- no pollution
- provide immediate response to increased demand
- reliable unless drought
- no fuel costs
- minimal running costs
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
Wave power
- many small wave powered turbines around coast
- turbines connect to generator to generate electricity when moving
Advantages of wave-power
- no pollution
- no fuel costs
- minimal running costs
Disadvantages of wave-power
- disturbing seabed + habits of marine animals
- spoiling view
- hazardous to boats
- unreliable - waves die went wind drops
- high initial costs
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
Advantages of tidal barrages
- no pollution
- mostly reliable - always 2 tides a day
- no fuel costs
- minimal running costs
Disadvantages of tidal barrages
- prevent free access of boats
- spoil view
- alter habitat of wildlife
- somewhat unreliable - size of tides vary
- high initial costs
Bio-fuels
Plant products or animal dung burnt to produce energy or run cars
Advantages of bio-fuels
- carbon neutral if plants grown at same rate as being burned
- mostly reliable - crops take short time to grow
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
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
Advantages of a power plant
- cheaper running costs
- low fuel extraction costs
- cost effective
Disadvantages of power plants
- high set-up cost
- environmental problems
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
Effects of acid rain
- harm to trees/soils
- harmful to ecosystems
How to reduce acid rain
- take out sulfur before burning fuel
- clean up emissions
Effect of oil spillages
Affects mammals/birds living around sea
What has happened to use of electricity in UK
It has slowly decreased since the beginning of the 21st century
Why has electricity usage slowly decreased since the start of the 21st century
Appliances have become more efficient
Reasons for burning fossil fuels
- electricity generation
- fueling cars with oil
- heating homes + cooking with gas
Why do people want to use more renewable energy
To protect the environment
What limits use of renewables
- reliability
- money
- politics
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
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
