Physics P1

Physics P1

1. Transferring energy

   • Colours
     • Dark/Matt - Good radiation emitter and absorber
     • Light/Shiny - Bad radiation emitter and absorber
   • Methods
     • Conduction - When particles in a solid vibrate and collide
     • Convection - When particles in al liguid or gas are given more energy, they spread out so the hot material rises
     • Radiation - All particles emit infra-red radiation
     • Evaporation - When a liquid gains more energy and escapes as a gas (Increased by temperatur, surface area and wind)
     • Condensation - When a gas loses energy it returns to a liquid
   • U-Values
     • They tell us how much heat passes through a material. Lower=Less heat
     • Energy loss(J) = U-value(W/M^2/°C) x Area(M^2) x Temperature difference(°C)
   • Specific Heat Capacity
     • How much energy is require to raise the temperature of an object by 1°C
     • Energy(J) = Mass(Kg) x SHC(J/Kg°C) x Temperature change(°C)

2. Energy efficiency

   • Energy cannot be created or destroyed only transferred.
   • We use sankey diagrams to represent energy efficiency

3. Electricity

   • Cost
     • We need to know the energy transferred in a given time
       • Energy transferred(J) = Power(W) x Time(S)
     • We also need to know kilowatt-hours
       • Energy transferred(KWH) = Power(KW) x Time(H)
     • 1 Watt = 1 Joule/Second
   • Generating Electrcity
     • Non-Renewable
       • Fossil fuels (Coal, oil, gas)
       • Nuclear fission (The splitting of atoms)
     • Renewable
       • Wind - Turbines drive generators. Many are required and the wind is unreliable but the turbines require very little maintenance
       • Hydroelectric - Falling water from rivers or reservoirs turn turbines. it is reliable but dams are expensive to construct
       • 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
       • Waves - The rise/fall of waves drives turbines but it is unpredictable and very rarely used
       • 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
       • 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
   • The national grid
     • When energy travels along a wire some disspates. Increasing the voltage reduces the energy lost. Transformers are use to in crease/decrease the voltage

4. Waves

   • Types
     • Transverse - The oscillations are at aright angle to the direction of travel and energy transfer
     • Longitudinal - The oscillations are in the same direction as the travel and energy transfer
   • Electromagnetic
     • All these transverse waves travel at the same speed in a vacuum and form a continuous spectrum
   • Reflection - When a wave bounces off an interface between two materials. The wave changes direction but doesn't cross the interface
   • Refraction - When a wave crosses an interface between two materials. The wave changes direction unless the rays hit the interface at right angles
   • 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
   • Mirrors
     • The angle of incidence is equal to the angle of reflection

5. The Universe

   • Doppler Effect
     • If a source is moving towards us we hear a high-pitched sound
       • Because Waves in front of a source become squashed so frequency increases and wavelength decreases
     • If the source is moving away from us we hear a low-pitched sound
       • Because waves behind a source become stretched so frequency decreases and wavelength increases
   • Expanding
     • Red-Shift
       • 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
       • This used as evidence as for the big bang (expansion from a single point)
     • Cosmic Microwave Background Radiation (CMBR)
       • Is found throughout the universe and shows how the wavelengths have increased over time

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