P2 (part one)

a&b
1. photocells
  1. convert light into electricity
  2. larger SA, more electricity produced
    1. more sunlight can be absorbed
  3. useful when mains not avalable
    1. remote areas
      1. where electricity is expensive
  4. produces dc
    1. one direction
  5. advantages
    1. robust
    2. little maintenance
    3. no fuel required
    4. no polluting waste
    5. no power cables
    6. uses renewable energy resource
    7. long-life
  6. disadvantages
    1. no electricity when dark or bad weather
    2. quite expensive
  7. light intensity
  8. SA exposed
  9. distance from light source
passive solar heating
1. in the day
  1. sun heats floors and walls
2. at night
  1. the heat is radiated back from walls and floors
greenhouses
1. the sun is very hot
  1. so has short wavelength
    1. the glass of the greenhouse is transparent to the suns radiation
      1. the material absorb radiation and heat up
        reradiated infrared radiation cos they're are cooler and have longer wavelength
        reflected back
wind power
1. result of sun heating the earth
  1. creating convection currents in the earths atmosphere
2. winds ->
  1. blades ->
    1. generator
3. advantages
  1. robust
  2. renewable resource
  3. dont pollute
4. disadvantages
  1. ugly
  2. noisy
  3. shut down at high wind speeds
  4. needs space
dynamo
1. generates electricuty
2. increased by: stronger magnetic field, more turns on coil, faster movements.
3. ac- slip rings motor-split rings
4. moving coil near magnet or moving a magnet near a coil
5. coil of wire is free to rotate between the poles of a magnet (close) as coil rotates, it cuts thee magnetic field and a current will pass through the coil a current is induces and movement is essential)
6. freq. no. complete waves passing a point in 1sec
  1. the ac from generator has a freq.
7. output can be displayed on an oscilloscope
  1. shows how current produced by dynamo changes over time
  2. time for one complete cycle is called the period of alternating curent
  3. height is the mx./peak voltage
    1. length of wave represents time for one cycle
    2. frequency (hz) .= 1/period(s)
national grid
1. source of energy are power stations
  1. fuels are used to heat water
    1. water boils to produce steam
      1. steam at high pressure turns a turbine
        turbine drivesa generator
        generator produces electricity
        then step-up transformer (less energy loss)
        power lines etc.
        step-down transformer
        consumers (homes, schools, farms etc)
greenhouse effect
1. earths atmosphere traps energy; alike a greenhouse
2. atmospheric gases let short wavelength uv to pass through
  1. infrared radiation; long wavelength; is radiated back from warmed surface of earth
water vapour; carbon dioxide; methane
1. natural sources
  1. water vapour
    1. evaporation of large bodies (e.g lakes)
    2. transpiration
  2. carbon dioxide
    1. fermentation
    2. respiration
    3. volcanic eruptions
  3. methane
    1. decomposition of organic matter (wetlands)
    2. formation of fossil fuels (coal)
    3. termites
2. manmade sources
  1. water vapour
    1. 0.001% human activity
  2. methane
    1. cows
    2. rice paddies
    3. mining and burning of fossil fuels
    4. burying waste on landfill
  3. carbon dioxide
    1. burning solid fuels (eg. coal/oil/gas)
    2. incineration of waste
    3. cement manufacture
    4. deforestation
3. environmental issues
  1. factories produce smoke which reflects radiation from the cities, back to earth, warming it up
  2. volcanoes emit ash when they erupt, which stops the suns rays reaching the earth, thus cooling down the earth

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P2 (part one)

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	Created by abbie Fitzpatrick about 9 years ago