physics p1 part 1

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  • Physics P1 part 1
    • Evaporation and Condensation
      • evaporation is a liquid changing to a gas
        • to evaporate, particles need enough energy from heat to break away from eachother
      • condensation is when a gas cools and changes to a liquid
    • Insulating Buildings
      • u values show how well something acts as a thermal insulator - lower is better
      • insulation saves money
      • payback time is the time it takes to save as much money as the insulation costs
      • single and double glazed windows
      • cavity walls are walls with insulation in the middle
    • Conduction and Convection
      • conduction is transfer through solids when they are heated
      • convection is the main way energy is transferred through liquids and gases
        • convection currents work because hot liquids and gases rise and then when they cool down they become dense again and sink
    • Infrared Radiation
      • all objects emit it
        • measured with a thermopile
      • leslie cube
      • black surfaces emit more than white
      • dull surfaces emit more than shiny ones
    • Waves
      • longitudinal waves oscillate in the same direction the waves travel
      • transverse waves oscillate at right angles to the direction the wave travels
        • top is peak, bottom is trough, amps is up and down half a wave and wavelength is across a whole wave
    • Kinetic Theory
      • describes the energy of particles and the way they move
      • Particles vibrate more when they are getting hot and melting or evaporating
    • Sound
      • is vibrating particles and is transferred when it reaches your ear drum. this is how you hear sound
      • Longitudinal waves
      • Amplitude is volume and is measured in amps
      • Frequency is pitch and is measured in hertz
    • Rate of Energy Transfer
      • depends on...
        • material
        • size and shape
          • a large surface area transfers energy faster
        • type of surface
        • the temperature difference between surface area and its surroundings
    • Renewable Energy
      • 'energy from waste' power stations burn waste that cant be recycled
      • Wind turbines
        • connected to generator
      • Hydroelectric power stations use falling water to turn turbine blades
      • Solar power
        • When there is no wind for turbines or sun for solar power, theres a solution. when too much power is produced it is used to heat and pressurise gas so hot gravel stores energy. When energy is needed, the gravel is cooed and the energy drive the turbine
      • Rocks deep underground are hot and in volcanic areas steam sometimes rises to the surface and geothermal powerstations use it to drive turbines
    • Specific Heat Capacity
      • the energy needed to raise the temperature of 1kg of a material by 1 degree in joules
      • J/Kg degrees celcius
      • Energy transferred in joules = mass in kg x temperature change x specific heat capacity in J/Kg degrees celcius
    • Powerstations
      • about 35% efficient
      • new fossil fuel powerstations are combined cycle gas turbine power stations which are 50% efficient
      • Nuclear power stations use a nuclear reaction instead of burning fuel to change water to steam
      • fuel is burned to heat water that evaporates to steam. steam drives around turbine. it condenses and is returned back to boiler and repeats
        • the turbine turns the generator which generates electricity. then the step up transformer increases the voltage of electricity to very high voltages needed for national grid. it goes to a pylon which goes to the national grid
    • Energy
      • stored and transferred
      • Eg, water cycle
    • Electrical appliances
      • Energy transfers from a power station to places as an electrical current
      • Electrons in the metal the cables are made of transfer charge down the line. The rate at which this happens is measured in amperes (A)
    • Energy Transfer and Waste
      • Shown in a sankey diagram
    • changing direction
      • reflection
      • diffraction
      • Refraction
    • light and mirrors
      • The normal is the line perpendicular to the mirror
      • The incident ray is the line that hits the mirror from the light
      • The reflected ray is the reflection of the incident ray
      • Between the  normal and the waves are the angles of incidence and reflection. these are equal
    • Efficiency
      • useful energy/ power out divided by total power or energy in
      • Power is the rate of energy transfer
        • Power is measured in watts
  • The cost of electricity
    • charged for the number of kilowatt hours
      • KWh = KW x h

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