Physics P3

Physics P3

Electrical energy
1. Energy is transferred from cells
2. Power=rate of energy transfer
  1. Energy transferred=power X time
3. Kilowatts
  1. Energy transferred in kilowatt hours
    1. Energy transferred= Power X time (in hours)
Electrical energy
1. Power= Voltage X current
2. efficiency = Energy usefully transferred/ Total Energy supplied X 100
Saving energy
1. Stop heat escape housing
  1. Installing cavity wall, loft insulation, Double glazing and drought proofing
    1. Expensive to do so
2. Turn lights off, energy saving light bulbs
Energy sources
1. Non renewable
  1. Fossil fuels
    1. C02 global warming
      1. Acid rain damages trees' soil
        Oil spillings damage ecosystems
    2. However these are cheap and make lots of energy
  2. Nuclear fuels
  3. Will run out damage to environment
2. Renewables
  1. Wind/ wave/ tides/hydroelectic/solar
    1. Wind
      1. turbines have own generator
        Wind turns them.
      2. No pollution
        Do spoil view
      3. 1500 turbines to replace one coal power station
      4. Can be noisy
      5. initial costs high
      6. Wind stops, power stops
    2. Solar
      1. Energy made from sunlight
        No pollution
        Sunny countries Very good
        Remote places
      2. Expensive initially
      3. Not practical
    3. Wave
      1. Lots of small turbines
        No pollution
        Damage to the view
        Hazards to boats
        Never used large scale
      2. Tidal, big dams with turbines
        Tide comes in drives turbine
        Energy is sun and moons gravity.
        No pollution
        Spoils view alters habitat
    4. Hydroelectic
      1. Flood a valley
      2. Costs high
        No pollution
      3. Water stored, above turbines in dam
        Gravity pulls water down through turbines
        generator converts movment (kinetic) of turbine into electicity
  2. Biofuels Geothermal
    1. Biofuels
      1. Burnt to heat water, make steam, spins turbine
      2. Plant waste
      3. Plants take in co2 but expel it when burn, balance process
    2. Geothemal
      1. Hot rocks
        water pumped down to hot rocks, returned as steam, drives turbine
      2. Costs to drill down to rocks
  3. Never run out
Generators
1. Moving magnet in coil of wire
  1. induces a voltage
    1. This is called electomagnetic induction
      1. As you move magnet magnetic field through the coil changes
        This change induces a voltage, and a current flows in the wire
2. Magnet spins in coil of wire
  1. magnetic field changes
    1. inducing voltage
      1. Spin magnet faster
        requires more energy from turbine
National grid
1. Network of pylons and cables
  1. Electrical energy taken to homes
2. Allows energy to be generated anywhere on the grid
3. Huge amounts need either a High current or High voltage
  1. Problem with a high current
    1. lots of energy lost with heat
  2. Much cheaper to transport with high voltage
    1. keeps current very low
      1. Reduces energy lost
    2. Voltage needs to be reduced before it gets to homes

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