Energy

• System


  An object or group of objects
• When a system changes


  The way energy is stored also changes
• Ball rolling and hitting a wall

  • Moving ball system
  • Kinetic energy transfers to sound
• Vehicle slowing down


  • Moving vehicle system
  • Kinetic energy transfers to thermal due to friction
• Specific Heat Capacity


  • The energy required to raise the temperature of 1kg of a substance by 1°C
• Power


  • The rate at which energy is transferred or the rate at which work is done
• An energy transfer of 1 joule per second is equal to a power of 1 watt
• If given two motors A and B

  The motor that can do the same work faster is more powerful
• Energy can be transferred usefully, stored or dissipated but cannot be created or destroyed
• In all system changes energy is dissipated, so that it is stored in less useful ways. This energy is often described as being 'wasted'
• Reducing energy waste


  • Lubrication
  • Thermal insulation
• Thermal conductivity


  The higher the thermal conductivity of a material, heat is allowed to travel through the material more easily, so the higher the rate of energy transfer by conduction across the material
• Thermal conductivity in a building

  Rate of cooling is low if walls are thick and thermal conductivity of the walls are low
• If the walls are thin metal sheets, heat would be lost very quickly
• Efficiency


  • The ratio of the useful work done by a machine, engine, device, etc, to the energy supplied to it, often expressed as a percentage or is less than 1
  • eff=useful output/total input
• Ways to increase efficiency

  • Reducing waste output
  • Recycling waste output
• Main energy sources


  • Non-renewable: Fossil fuels, Nuclear fuel
  • Renewable: Biofuel, Wind, Hydro-electricity, Geothermal, Tidal, Solar, Water waves
• Renewable energy


  Energy which can be replenished as it is used
• Non-renewable energy


  Used more for large-scale energy supplies due to the large energy output per kilogram of fuel
• Renewable energy has become more important due to the finite lifetime of fossil fuels, and so their development has become more important
• Renewable energy is not always the most reliable as: solar doesn't work in bad weather or night, wind is only intermittent
• Main energy uses


  • Transport
  • Electricity generation
  • Heating
• Environmental impact of energy

  • Extraction: Fossil fuels destroy landscapes, wind turbines can be eyesores
  • Use: Fossil fuels release harmful emissions, solar and wind create electricity with no emissions
• During industrial revolution, fossil fuels became an important source of energy as it was easy to mine, and provided a lot of energy
• Only recently has renewable energy become more suitable – technology has had to develop a lot since industrial revolution to be able to harness such energy sources efficiently
• It is easier to use energy resources due to increasing pressure to cope with the public's increasing power demands but harder to solve environmental issues due to political, social, ethical and economic considerations