P2

P2

1. sun energy

   • heat and light source
   • photocells
     • more surface area
       • intense sunlight
         • closer to light
     • DC current produced
       • energy absorbed causing electrons to be knocked loose from silicon crystals. These electrons will flow freely in an electric current.
       • panel to be effective must track the rotation of the sun
   • can also create solar heaters
     • curved mirrors used to pinpoint energy
       • passive solar heating captures sun energy and doesn't convert it etc greenhouse.
         • glass is transparent to some sun radiation. visible light is emitted in the room then it heats up the objects inside that then heat up and emit infrared. infrared heat is emitted against the glass and reflected back in warming the room.
           • infrared is a higher wavelength.
   • wind turbine
     • sun heats up the air causing a convection current.
       • the convection current increases the KE of the wind. turbines convert KE to electrical energy

2. generating electricity

   • dynamo effect
     • electricity can be generated by moving a magnet in a coil. the coil interacts wih the field of the magnet causing an AC current
     • effected by
       • stronger magnet
         • more coils
           • faster movement of magnet
   • Generators create AC current and batteries create DC. AC current means the direction of current changes direction every time the magnet changes direction
   • power stations
     • National grid is where all the electricity is transferred to the homes.
     • crude oil can be burned
       • nuclear uranium rods emit energy in fission
         • biomass can be burnt or fermented to produce methane gas.
           • absorbs cO2 in production so equal pollution. slower to grow and doesnt release much. takes land. 10% is explosive
       • the heat from the source boils water and the steam turns a turbine. turbine is part of the generator.
     • very ineffecient due to lose of energy in heat

3. global warming

   • some gases in the atmosphere do not allow heat to escape so the earth warms up. in particular long wavelength infrared.
     • co2, water vapour, methane
       • natural and man made.
   • short wavelength (visible light, infrared, and UV) can pass through the atmosphere. This is the absorbed by Earth and heats it. the earth is cooler than the sun so it emits long wavelength infrared rays that are absorbed by greenhouse gases.
   • methane absorbs 4x the amount of CO2. But CO2 levels are rising much faster than any levels of gases.
   • Climate change.
     • CO2 is increasing due to
       • Deforestation
         • dust from volcanic ash reflects the suns heat back away from earth
       • fossil fuels burning
         • dust from factories also reflect heat from cities.
       • car pollution
       • population
     • as earth warms up wind patterns and weather patterns change.
       • droughts, flooding, hurricanes, lower rainfall are all effects
   • Evidence
     • no thermometers centuries ago so have to use tree ring thickness.
       • increased mostly in last two years
     • scientists still measuring temperature in different nations.
     • disagreements as some think it may be sun spots or 1000 year cycles

4. fuels for power

   • Watts: 1 watt is the transfer of 1 joules of energy per second
     • Power (watts)= Current (A) x Voltage (V)
       • Kw = Kilowatt (1000 watts)
   • Off peak electricity
     • electricity is supplied 24/7 and cant be stored
     • cheaper electricity a night to make use of the wasted energy
       • washing machines, dish washers, storage heaters etc...
   • Electricity meters
     • units are kilowatt hours kWh
     • amounts of units used depend on - power rating in Kw of the appliciance. And the time its on for.
     • Total cost = No of Kilowatt hours x Cost of one kWh
       • Energy supplied (number of kilowatt hours) = Power rating (Kw) x Time (h)
   • Transformers
     • for efficiency the national grid is fed through transformers. the voltage is increased on entrance/ step up (so current decreases) so that less heat is created on the national grid.
       • cost efficency
   • comparing fuels
     • Fossil fuels
       • enough reserves for short to medium time. Relatively cheap and easy to obtain. short start up time. flexible in meeting demands. gas doesn't produce SO2.
       • produces CO2, and SO2. removing those waste gases cost moneys. risk of oil spillages. expensive pipe lining needed
     • Biomass
       • renewable. burning produces heat. fermentation creates methane for burning
       • Produces CO2
       • large area of land needed could be used for food.
     • Nuclear fuel
       • cost and rate of fuel is cheap
         • can be placed in sparsely pulated places. flexible in meeting demands. no CO2 or SO2. high stocks of nuclear fuels.
       • material takes centuries to stop emmiting. storing is expensive. building and decommisioning is expensive. long start up time. radiation can be emitted. pollution from fuel processing. high maintenance.
     • renewable sources.
       • no fuel costs. no chemical pollution. often low labour. no contribution to global warming or acid rain. clean electricity. can be made in remote areas.
       • only hydroelectric produces great quantitys. lots of space and ugly. unreliable weather permting. high maintenance and installation costs.

5. nuclear radiation

   • radioactive materials are substances that emit radiation no matter what occurs to them
     • involves either alpha, beta or gamma radiation
       • alpha radiation
         • most smoke detectors contain americum-241 which emits alpha radiation. the radiation ionises he gas inside which is the attracted to the poles on the circuit causing a full circuit. if there is smoke particles inside the space they absorb the energy. if there is a drop in current then an alarm is set off.
       • Beta
         • tracers are made using beta emition. hey can be used in medicine to detect where a tumour is. to identify where minerals in a plant are for better fertiliser production. in paper thickness gauge
       • gamma
         • destroys cancerous cells. high calculated dose is fired at the tumour from multiple angles so healthy cells aren't killed.
           • sterilise medical equiptment. kills microbes without heat so no damage done to equiptment.
             • non destructive tests on wields. gamma ray emitter placed on one side and gamma ray source on the other side. a detector on the other side is used to see cracks.
     • can cause ionisation. which is bad in the body as it breaks molecular bonds and damages cells.
     • penetrating power
   • radiotherapy is a treatment for cancer by killing cancer cells. careful not to kill healthy cells
     • radioactive waste from hospitals and power stations can affect living cells and cause cancer.
   • waste.
     • llow level waste is disposed by sealing and burying in land fills.
     • high level is mixed with sugar, bonded with glass and poured into a steel cylinder then kept underground.
     • some waste can be reprocessed

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