GCSE Physics

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GCSE Physics
2012-06-19 13:11:37
energy efficiency electrical devices

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  1. give two reasons why we should try to reduce wasted energy
    • Reducing wasted
    • energy will save money, and it will also reduce the amount of carbon dioxide
    • being put into the atmosphere
  2. how will keeping our homes cooler reduce wasted energy
    • If the air in the building is cooler, then the
    • temperature difference between inside and outside is less and the energy
    • transfer from inside to outside will be less.
  3. what information would you need to allow you to work out whether buying a more expensive LED light instead of a normal bulb would save you money overall
    • The price of normal
    • and LED bulbs, the amount of energy each type uses, and the average time each
    • one lasts before it needs to be replaced
  4. How does fittting a heat exchanger to the ir circulation sysetm in a factory help to save money and help the environment
    • It increases the
    • temperature of the air coming into the building, so that less energy has to be
    • used for heating
  5. what does cost effective mean ? Explain some of the factors you would consider in deciding whether replacing a central heating boiler will be cost-effective
    • A cost-effective
    • measure is one that will eventually save more money than it costs. If a boiler
    • is being replaced, the owner needs to know how much the new boiler will cost to
    • buy and install, and how much energy it will use. They need to compare the
    • energy used with the old boiler, and the price of energy. These values will
    • allow them to work out how much money the new boiler will save per year. They
    • can then work out how many years it will take to save the money that the new
    • boiler costs. It may not be worth spending the money on a new boiler unless the
    • one being replaced is old and may need replacing soon anyway. 
  6. the increasing ownership of toasters could help to reduce the amount of electricity used . Explain this statement
    • A toaster has the
    • heating elements very close to the bread, so not much energy is wasted. A grill
    • has a much larger heating element and so is likely to have a higher power.
    • Unless a lot of toast is being made some of the element will just be heating
    • air and so wasting energy. So, although some electricity will have been used
    • when the toaster was made, taking into account the savings in electricity use
    • when a toaster is used instead of a grill, owning a toaster could save on
    • electricity use overall.
  7. explain why the two different units for measuring energy are used
    • Joules and
    • kilowatt-hours. Joules are used when the amounts of energy are small (or when
    • working out energies for scientific investigations); kilowatt-hours are used
    • when working out how much energy appliances have used.
  8. what is a unit of electricity
    • The amount of energy
    • equivalent to one kilowatt-hour.
  9. explain how electricity is charged for , and how to calculate the energy used by an appliance and the cost of electricity
    • Electricity is
    • charged by the amount of energy used. The energy used by an appliance depends
    • on its power rating, which is the energy used every second. The energy used is
    • found by multiplying its power rating in kilowatts by the time for which it is
    • used in hours. This gives the energy in kilowatt-hours. The cost is found by
    • multiplying this energy by the cost per kilowatt-hour.
  10. explain why electricty is not a source of energy
    • Electricity has to be
    • made using other forms of energy; these other forms are the energy sources.
  11. explain why fossil fuels are reffered to as non-renewable fuels
    • We are using fossil
    • fuels much faster than they are being formed, so we will eventually run out
  12. why are biofuels reffered to as renewable fuels
    • Most biofuels are made from plants or from animal waste;
    • new plants can be grown to replace the ones used to make biofuels.
  13. name two nuclear fuels
    Uranium, plutonium
  14. describe two differences between a fossil fuelled power station and a nuclear power station
    • Any two from:
    • different fuels, nuclear power stations do not burn their fuel, nuclear power
    • stations have lower fuel costs.
  15. some power stations use stored energy to make steam . Which kinds of stored energy are used
    Chemical and nuclear.
  16. what are the stages in a coal-fired power station
    • energy stored
    • chemically in fuel, transferred by burning in furnace, to heat water,
    • transferred to motion (kinetic energy) in the steam produced, transferred to
    • movement of turbines/generator, transferred to electrical energy.
  17. list the ways in which coal fired power stations can cause pollution
    • They produce carbon
    • dioxide, sulfur dioxide, nitrogen oxides, dust and ash
  18. describe how pollution from fossil-fuelled power stations can be dealt with
    Sulfur is removedfrom the fuel before it is burnt, or the sulfur dioxide is removed from wastegases. Nitrogen oxides are reduced by using special kinds of furnace. Smoke anddust is removed from the waste gases.CCS - carbon dioxide can be collected from power stations before it is released into the atmosphere , it can then be pumped into empty gas fields and oil fields like those under the North sea . It can be safely stored without adding to the greenhouse effect
  19. describe two advanatges of using natural gas instead of coal to generate electricity
    It produces lessnitrogen oxides and no sulfur dioxide, and gas-fired power stations are moreefficient so they produce less carbon dioxide for each unit of electricityproduced. Some students may add that gas can be transported to power stationsin pipes, whereas coal must be transported by rail
  20. explain some disadvanatges and advnatages of nuclear power
    • Advantages: they do
    • not emit carbon dioxide or other polluting gases; the fuel is cheaper per unit
    • of electricity produced; the fuel will last much longer before we have used it
    • all up. Disadvantages: it is difficult to deal with the radioactive waste; they
    • are more expensive to decommission; they are more dangerous if there is an
    • accident
  21. suggest why a nuclear power station costs more to build than a fossil fuelled power station
    • It needs extra
    • shielding to contain radioactivity in case of an accident
  22. why is decomisioning a nuclear power station properly important
    • To make sure no
    • radioactivity escapes into the environment.
  23. how can a nuclear accident affect people in parts of the world very distant from where it occurred
    • Radioactive dust can
    • be blown very long distances.
  24. how can electricty be produced using the wind
    • The wind is used to turn turbines, which generate
    • electricity.
  25. how can electricity be produced directly using the suns radiation
    • Solar cells can
    • produce electricity directly.
  26. describe four differeny ways in which water can be used to generate electricity
    • Hydroelectricity,
    • using water flowing from a dam; tidal barrage, which traps water at high tide
    • and lets it flow out through turbines; tidal stream, where turbines are placed
    • beneath water level in tidal currents; wave power, where waves force air up and
    • down a tube and the air turns turbines, or where a machine is moved by waves
  27. describe two different ways in which solar towers can be used to generate electricty
    • Sunlight can be
    • focussed onto a furnace, to heat water to make steam. The steam is used to turn
    • turbines.
    • OR
    • Sunlight heats up air beneath a transparent canopy, setting up a
    • convection current. The moving air is used to turn turbines
  28. describe how a geothermal power station works and compare it with a fossil-fuelled power station
    • A geothermal power
    • station uses hot water or steam from volcanic areas. Pipes sometimes have to be
    • put in the ground to allow the steam to rise. The steam is used to drive
    • turbines that drive generators. A fossil-fuelled power station also uses
    • steam/works in a similar way, except that the energy needed to produce steam is
    • transferred from burning fossil fuels
  29. some wind farms are built in the sea . What problems might this cause
    • They might be a
    • hazard to ships
  30. what effects might a tidal barrage have on scenery shipping and wildlife
    • (a)
    • The barrage would be visible from long distances. (b) Ships would not be able to get through the barrage unless
    • special locks are built. (c) Fish
    • migrations may be prevented, the changes in water levels might affect plants
    • and animals living in or on mud/sand in the estuary, and this might affect
    • birds or other animals further up food chains.
  31. suggest how a wave poer generator may affect the environment
    • They may be visible
    • from the shore, but the main impact is likely to be a possible hazard to
    • shipping.
  32. what are the advanatges and disadvantages of burying power cables underground
    • Advantages: does not
    • cause visual pollution, protected from the weather; disadvantages: more
    • insulation is needed, it is more expensive to install, and it is harder to find
    • faults.
  33. define national grid
    the system of power stations , cables , and transformers that transfer electricity all over the country
  34. an advert for solar cells claims that any electricity that the homeowner does not use can be sold to the national grid . Explain why this is not entirely correct
    • If a house is not already connected to the National Grid
    • (because it is in a remote location), it may not be economic to connect it; electricity
    • cannot be sold if there is no connection.
  35. why can't power engineers just use hydroeelectricty to meet sudden demands ?
    there are not enough hydroelectricity power stations to gnerate the extra amount of electricity required
  36. Jenny lives on her own and uses her tumble dryer once a week . Sam has threeyoung children and uses her tumble dryer every day . Explain who is more likely to benifit from buying a new , more effecient tumble dryer
    • Sam: both people will
    • save the same amount for each use of the more efficient machine, but as Sam
    • uses it more often her total savings will be more