P8.2 Flashcards
What are energy sources?
Something that we can use for heating, transportation or generating electricity
- renewable = doesn’t run out
- non - renewable = runs out as it’s being used faster than its being made
What are the 3 main uses of energy sources?
- heating (fossil fuels ; biofuels, sun and geothermal)
- transportation (fossil/biofuels)
- generating electricity (all of them)
How can we heat our houses?
- building houses that max heat from sun (large windows on south)
- solar panels
- use hot water from underground in some areas
How can we generate electricity?
- using photovoltaic cells (solar cells)
- use turbine and generators driven by wind, waves, geothermal, hydroelectric or biofuels
What are some examples of non renewable energy sources?
- run out and damage environment
- fossil fuels (coal, oil, natural gas) and nuclear fuels (uranium and plutonium) and often peat as it can’t be easily replaced
- we get most of our energy from this
How are fossil fuels formed?
- effect of temp and pressure acting on the remains on living things for over millions of years
What do power stations use to drive a turbine?
- steam
- as fossil fuels burn in O2, the energy in its chem energy store is transferred to thermal energy store of the water
- water boils to form steam, which turns a turbine and transferring energy to ke store of the turbine
- as turbine revolves so does the generator (think of as a big alternator)
- generator transfers energy electrically away from the power station via the national grid
What are nuclear reactors?
- a nuclear power station is mostly the same as a power station but the energy from nuclear fission is used to het water to make steam to drive turbines so main diff = the boiler which has fuel rods
- nuclear power stations take the longest time of all power stations to start up and natural gas power stations take the shortest time
How can non renewable resources cause environmental problems?
- all fossil fuels release CO2 (coal the most, then oil, then natural gas) and CO2 = climate change and global warming
- burning coal and oil release sulfur dioxide = acid rain (reduced by taking out silver before it’s burned/ cleaning up emissions)
- coal mining makes a mess of landscapes = esp open cast mining
- oil spillages = serious environmental problems
Why are nuclear power stations expensive even if the cost of nuclear fuels such as uranium are relatively low?
- nuclear waste (from nuclear power stations) = very dangerous and difficult to dispose off so even if nuclear fuel (uranium) is cheap the overall cost is high due to cost to build and decommission power plants
- nuclear power = rise of major catastrophes (Fukushima in Japan)
Give examples of renewable sources:
- never run out
- most of them do some damage but in less ways than non renewable
- don’t provide as much energy as non- renewables and weather dependent can be unreliable
- biofuels, wind power, sun, tides, waves, geothermal and hydroelectric
How are biofuels made and what are their advantages?
- made from anything (farm waste, animal dropping, landfill rubbish, specially grown crops)
- renewable as we can grown more and be burnt to produce electricity/ or run cars in the same way as fossil fuels
- carbon neutral (only works if you’re growing at the same rate)
- reliable as grow fairly quickly
What are disadvantages of biofuels?
- don’t grow very fast for immediate energy demands (can stock pile)
- high costs to make it and growing crops for biofuels means = no space / water for crops that are grown for food
- large areas of land are cleared to grow biofuels = losing their habitats and decay and burning of vegetation increase CH4 and CO2 emissions
How do wind turbines work and what are the advantages of them?
- using lots of little wind turbines = generate wind power
- each wind turbine has generator inside with rotating blades o turn generator and produce electricity
- no pollution (except for when they’re manufactured)
What are the disadvantages of wind turbines?
- spoil the view
- very noisy = annoying for people who live nearby
- only work when it’s windy (weather dependent) so you can’t always supply electricity or respond to high demand = not very reliable
What are the advantages of solar cells?
- made from special materials that release electrons when light falls on them = generator an electric current
- solar power is often used in remote places (Aussie outback) and to power electric road signs and satellites
- no pollution (take a lot of energy to make though) or environmental damage (except when making cells)
What are the disadvantages of solar cells?
- expensive
- mainly used to generate electricity on a small scale (homes)
- solar power is most suitable for sunny countries but can’t be used in cloudy countries like Britain
- can’t make it at night (weather dependent) and we can’t increase production when high demand = not very reliable
What can we use hydroelectricity for?
- building dams and flooding valleys
- producing Hydroelectricity = flooding a valley by building a big dam
- rainwater is caught and allowed through turbines
What are the disadvantages of hydroelectricity?
Advantage:
- immediate response to increased electricity demands as more water can be let through the turbines to generate more electricity
- high initial costs but minimal running costs so reliable energy source
Disadvantage:
- big impact on the environment due to flooding of valley and possible loss of habitats
What can we use tidal barriers for?
- uses Sun’s and Moon’s gravity
- tidal barriers = big dams built across river estuaries with turbines in them
- as the tide comes = fills estuary up and water is let out through turbines at a set speed
What are the disadvantages of tidal barriers?
- affect boat access
- spoil view
- alter habitat for wildlife (wading birds)
- variable height of tide and don’t work when the water level is the same on both sides
What are the advantages of tidal barriers?
- no pollution
- reliable as always happen twice a day
- only be used in some estuaries but have great potential
How has the use of electricity changed over the 20th century?
- past = used to use wood which was cheap and available but now increased use of HEP and nuclear power and biofuels have always been used
- use of energy sources increased as there is a higher population and more devices that use fuels
- most of this was from fossil fuels (coal and gas) and nuclear power
What are the issues with our current use of fossil fuels?
- fossil fuels = finite supply
- reserves of fossil fuels in hard to reach in many parts of the world (hard to find and extract and high price)
- burning fossil fuels = release CO2 = climate change and enhanced greenhouse effect
- climate change = ice caps melt, sea levels rise, flooding, extreme weather conditions and threats to food supplies
What are the issues with renewable resources?
- slow progress
- only 20% of fuel use is renewable as it generates less electricity and is mostly weather-dependent so amount supplied fluctuates
What renewable resources and techniques is the UK investing in to reduce fossil fuel use?
- using less non-renewable and make appliances more efficient to save energy
- oil used to fuel cars and gas to heat homes
- electric cars
- gov decides which energy source used depending on cost, environmental impact and how long the sources will last
- nuclear power instead of fossil fuels but the possibility of nuclear accidents and the dangers of nuclear waste
What is the national grid?
- system of cables, power stations, transformers and sub-stations that transport electricity across the country to consumers
How is an a.c and d.c produced?
- alternative voltage/p.d = p.d and current constantly change direction
- d.c = produced by direct voltage = current and p.d don’t change direction
Give examples of a.c and d.c.
- a.c = UK mains electricity a.c at 50Hz and 230V
- d.c = batteries and cells
What is an alternating current?
- the direction of voltage / potential differences is constantly changing/ reversing
What does a cathode ray oscilloscope (CRO) trace show and what does the height of the line show?
- how a p.d of a supply changes with time
- height at any point shows the input p.d at that point
What does a CRO show when connecting to alternating voltage and direct voltage?
- alt. V/p.d = wave (goes up and down in regular pattern) (same as a.c)
- d. v/p.d = horizontal line (doesn’t vary) (same as d.c)
How does the national grid transfer energy?
- electrically from high voltage in power stations (supply) to low voltages at home and industry (demand)
- powers stations to step up transformer to pylons to step down to consumers
Why is a high current not used when transferring electrical energy?
- transmit huge amount of power = need high V or I (P=VI)
- high current means you lose lots of energy when as wires heat up and energy is transferred to thermal energy store of surroundings
- wasted energy and power = costs money and is cheaper to boost p.d to very high and keep current very low = makes it efficient
How much is the national grid p.d boosted to at the power stations?
- 400, 000 V
What is power?
- energy transferred in a given time so higher power = more energy transferred
What happens if we don’t use transformers?
- changing the p.d reduces the heating effect which means less energy is lost to surroundings (heating depend on I and R)
- more energy lost in transmission = need to burn more fossil fuels in power station to transport to homes
What is the p.d and the current across the primary coil equal to?
Vp x Ip = Vs x Is
- p.d in primary coil (v) x current in primary coil (I)= p.d in secondary coil (v) x current in secondary coil (I)
- all transformers are nearly 100% efficient so input power = output power
How can we work out the power supplied to a coil?
power = p.d x current
- W = V x I
- input power = primary coil
- output power = secondary coil
What is the use of transformers in the national grid?
- get voltage up to 400 000 V for efficient transmission = use transformers with pylons and insulators
- p.d increased with step up transformer (more turns on secondary coil that primary)
- p.d reduced at consumer with step down transformer (more turns on primary than secondary)
Why is it important to lower the voltage back down?
- high voltage is dangerous
- would blow the appliances in our houses
What is the calculation of work out power loss?
P = I2R
- R = resistance or wires (reduce lose ease but using lower resistance wires)
How does electricity react our homes?
- generators in power stations generate an a.c and alt. p.d with 50Hz which reaches our homes through the national grid
- battery = direct voltage
What parts do plugs contain and what are their colours?
- neutral wire = blue
- earth wire = green and yellow
- live wire = brown
- fuse
What is the job of the live wire?
- live wire = carries the voltage (p.d.) and alternates between a + and - voltage of about 230V
- earth wire = is for safety and carries the current away of something goes wrong and at voltage of 0V
- neutral wire = completes the circuit = when appliance is operating normally, current flows through the live and neutral wire and around 0V
What is the p.d between the live wire and the neutral wire, the p.d between the live wire and the earth wire and the neutral wire and earth wire?
- live and neutral = equals the supply p.d (230 V for the mains)
- live and earth = 230V for mains connected appliance
- neutral and earth wire = at 0V as no p.d
What happens when you touch the live wire?
- body is also at 0V so if you touched the live wire, there would be a large p.d across your body and current would flow through
- this large electric shock could injure or kill you
Why is the earth wire necessary?
- electricity flows through anything that conducts
- live wire touches metal (case of appliance)= metal becomes live and you get electrocuted and could cause fires
- so appliances with metal cases must be earthed so the case must be attached to an earth wire so even if live wire touches metal case the current flows down earth wire into earth and not you
Why does the current flow down the earth wire and not you?
- earth wire is thick for low resistance which means the total R of circuit decreases
- current = p.d/R so this causes a big current to flow through live wire, the case (which also has low R) and the earth wire
- so if live wire touches metal case then the current flows into the earth wire as it has a lower resistance than you and a larger p.d
How does the fuse provide protection from the current?
- surge of current melted fuse = breaking the circuit and cutting off the live supply
- isolates the appliance so its impossible to get an electric shock from the case
- prevents fires caused by heating effect of large current
What do fuses and earthing protect?
- humans from getting electrocuted
- circuits and wirings in your appliances getting fried if there is a current surge
- fuses prevent fires
When is an earth wire not needed?
- if appliance casing is non- conductive (plastic) = then it’s double insulated
- anything double insulated doesn’t need earth wire and it can’t become live as no current can flow through case to you (have 2 boxes)
Why is there still danger of electric shock when the plug socket is off?
- current isn’t flowing but there’s still p.d in the live part of the socket
- if body could provide a link between the supply and the earth, you’ve made contact with it
Compare renewable and non-renewable resources:
- renewable energy sources can be used to generate energy over again without running out
- non renewable resources will eventually run out
- renewable energy sources such as solar and geothermal don’t generate greenhouse gases nor nuclear radiation so renewable energy sources don’t give rise to environmental problems such as global warming
- however unlike non-renewable sources of energy, renewable sources of energy such as solar and wind are unreliable
Explain why coal is non-renewable but wood is renewable?
- coal takes millions of years to form and therefore will run out in our life time given the high rate at which we are using it
- but wood forms in just years so it will be available to use in our lifetime
Explain why there are 2 types of ‘solar panel’
As there are 2 different energy transfers involved
- solar panels = light energy to heat energy
- solar cells (photovoltaic cells) = light to electrical energy
Explain why it is difficult to work out of using photovoltaic cells on your roof does or does not contribute of climate change
- cells themselves require energy to produce which is most likely generated by fossil fuels
- therefore the cells would only not contribute to climate change if over their lifetime, they produce more electrical energy than used to produce them
Why is their a similarity between biofuels and fossil fuels but not between biofuels and nuclear fuels?
- biofuels are similar to fossil fuels as both are made from plant/animal remains and need to be burnt to release their energy
- biofuels are not similar to nuclear fuels as nuclear fuel isn’t burnt but a nuclear reaction is carried out in order to release the fuel’s energy
Suggest why very little oil is used to generate electricity
- using oil in power plants to generate electricity is less efficient that using it directly in cars
Why will there always be an uncertainty in the prediction for when fossil fuels run out?
- they take millions of years to form and are buried deep underground
- so you can’t accurately account doe how many fossil fuels remain
Explain what might happen to the behaviour of individuals and governments as fossil fuels begin to run out
- as fossil fuels begin to run out = cost of fuel for cars and electricity will start to increase
- individuals will be/ are encourage to think about their energy use and to be mindful not to use energy unnecessarily (e.g turn off lights)
- in order to continue to meet demand for electricity, gov will need to invest money in developing renewable sources of energy
- although initially expensive to build, in the long term, renewable sources of energy will ensure electricity generation remains cost effective and affordable
Why are power lines supported by pylons have to be so high off the ground?
- power lines have a high p.d with respect to the ground
- so there is a high likelihood of current arcing to the ground
Explain why transformers need to be used in the National Grid?
- current in wires wastes energy by transferring some electrical energy as heat to surroundings
- to reduce energy loss = electricity is transferred at high voltage in the cabled of the National Grid
- increasing voltage of the electrical energy = reduces the current
- transformers are used to step- up the voltage after a power plant and to step down the voltage before homes/businesses (ac allows it to be stepped up and down)
What happens when you touch the earth wire?
- nothing as there is no p.d
- both are 0V so no current would flow
