Physics P1

Transferring energy
1. Colours
  1. Dark/Matt - Good radiation emitter and absorber
  2. Light/Shiny - Bad radiation emitter and absorber
2. Methods
  1. Conduction - When particles in a solid vibrate and collide
  2. Convection - When particles in al liguid or gas are given more energy, they spread out so the hot material rises
  3. Radiation - All particles emit infra-red radiation
  4. Evaporation - When a liquid gains more energy and escapes as a gas (Increased by temperatur, surface area and wind)
  5. Condensation - When a gas loses energy it returns to a liquid
3. U-Values
  1. They tell us how much heat passes through a material. Lower=Less heat
  2. Energy loss(J) = U-value(W/M^2/°C) x Area(M^2) x Temperature difference(°C)
4. Specific Heat Capacity
  1. How much energy is require to raise the temperature of an object by 1°C
  2. Energy(J) = Mass(Kg) x SHC(J/Kg°C) x Temperature change(°C)
Energy efficiency
1. Energy cannot be created or destroyed only transferred.
2. We use sankey diagrams to represent energy efficiency
Electricity
1. Cost
  1. We need to know the energy transferred in a given time
    1. Energy transferred(J) = Power(W) x Time(S)
  2. We also need to know kilowatt-hours
    1. Energy transferred(KWH) = Power(KW) x Time(H)
  3. 1 Watt = 1 Joule/Second
2. Generating Electrcity
  1. Non-Renewable
    1. Fossil fuels (Coal, oil, gas)
    2. Nuclear fission (The splitting of atoms)
  2. Renewable
    1. Wind - Turbines drive generators. Many are required and the wind is unreliable but the turbines require very little maintenance
    2. Hydroelectric - Falling water from rivers or reservoirs turn turbines. it is reliable but dams are expensive to construct
    3. Tidal - Seawater is trapped at high tide and then at low tide it is released which drives turbines. It is reliable but barrages are expensive to construct
    4. Waves - The rise/fall of waves drives turbines but it is unpredictable and very rarely used
    5. Geothermal - Water is superheated underground into steam which on the surface drives turbines. It is reliable but there are limited areas of use e.g. Iceland
    6. Solar cell - They turn sunlight into energy. They are expensive and only convert 20% of the Sun's energy. They only work when the sun is visisble
3. The national grid
  1. When energy travels along a wire some disspates. Increasing the voltage reduces the energy lost. Transformers are use to in crease/decrease the voltage
Waves
1. Types
  1. Transverse - The oscillations are at aright angle to the direction of travel and energy transfer
  2. Longitudinal - The oscillations are in the same direction as the travel and energy transfer
2. Electromagnetic
  1. All these transverse waves travel at the same speed in a vacuum and form a continuous spectrum
3. Reflection - When a wave bounces off an interface between two materials. The wave changes direction but doesn't cross the interface
4. Refraction - When a wave crosses an interface between two materials. The wave changes direction unless the rays hit the interface at right angles
5. Diffraction - When waves pass through a gap or over an obstacle that is similar in size to the wavelength of the wave. The wave spreads out through the gap
6. Mirrors
  1. The angle of incidence is equal to the angle of reflection
The Universe
1. Doppler Effect
  1. If a source is moving towards us we hear a high-pitched sound
    1. Because Waves in front of a source become squashed so frequency increases and wavelength decreases
  2. If the source is moving away from us we hear a low-pitched sound
    1. Because waves behind a source become stretched so frequency decreases and wavelength increases
2. Expanding
  1. Red-Shift
    1. When objects have longer wavelengths they move to the red end of the electromagnetic spectrum so therefore if we see more red the object is moving away from us
    2. This used as evidence as for the big bang (expansion from a single point)
  2. Cosmic Microwave Background Radiation (CMBR)
    1. Is found throughout the universe and shows how the wavelengths have increased over time

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