Physics - Energy

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  • Created by: Issy.ryan
  • Created on: 23-12-17 13:59
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  • Physics - Energy
    • Energy Changes
      • Kinetic Energy = 0.5 x mass x (speed)²  (E????=½mv²)
      • Gravitational Potential Energy = mass x gravitational field strength x height (E????=mgh)
      • Elastic Potential Energy = 0.5 x spring constant x (extension)² (E????=½ke²)
    • Specific Heat Capacity and Internal Energy
      • Internal energy  is the total kinetic and potential energy of all the particles that make up a system.
      • Doing work on a system, heats it, which changes energy stored in the system and the energy of the particles within it. As energy increases, it will increase the temperature or produce a change in state.
        • The temperature increase depends on;   - the mass of the substance heated             - what the substance is.         - the energy input
      • The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kg of the substance by 1?.
      • change in thermal energy = mass x specific heat capacity x temperature change (?E=mc?????)
    • Energy Transfers
      • In energy transfers; - energy can be transferred usefully, stored or dissipated (spread out to surroundings).                     - energy cannot be created or destroyed
        • In a closed system, the total energy never changes but it can be transferred from one store to another.
      • Wasted energy is caused by unwanted energy transfers and is no longer available for useful transfers.
        • Unwanted transfers can be reduced by;                      - lubrication, to reduce friction that produces heat     - tightening any loose parts, prevents unwanted vibration (sounds).          - thermal insulation, reduces heat loss.
      • The rate of cooling in a building depends on the thickness and conductivity of the walls.
    • National and Global Energy Resources
      • The main uses for energy resources are transport, electricity generation and heating.
      • All energy resources are either renewable (can be replenished) or non-renewable (will eventually run out).
      • Biofuel =  renewable, used for transport and electricity generation. Large areas of land are needed for growing fuel crops , at the expense of food crops for poorer places.
      • Wind  =  renewable, used for electricity generation. Doesn't provide a constant source of energy, turbines can be noisy./dangerous for birds, they're also unattractive in the countryside.
      • Water (hydro-electricity) = renewable, used for electricity generation. Requires large areas of land to be flooded, altering ecosystems and displacing locals.
      • Geothermal = renewable, used for electricity generation and heating. Only available in limited areas where hot rocks close to surface are found e.g Iceland.
      • Tidal = renewable, used for electricity generation. Tides unreliable, affect output. Expensive to build, alters habitats and causes problems for shipping.
      • Solar = renewable, used for electricity generation and some heating. Depends on light intensity, so no power made at night. Expensive compared to output.
      • Water-waves = renewable, used for electricity generation. Output depends on waves, so is unreliable. Can alter habitats.
      • Nuclear-fuel = non-renewable, used for electricity generation and some military transport. Produces radioactive waste, but no other emissions. Expensive to build and decommission, reliable output.
      • Coal = non-renewable, used for electricity generation, heating and some transport. Burning produces greenhouse gases (CO? and acid rain, SO?). Reliable output.
      • Oil = non-renewable, used for transport and heating. Reliable output, provides a compact energy source  for transport. Burning produces CO?, NO? and SO?. Serious environmental damage if spilt.
      • Gas = non-renewable, used for electricity generation, heating and some transport. Reliable output, burning produces CO? but not SO?.

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