Energy

• Types of energy

  • Gravitational potential energy
  • Electrical energy
  • Elastic potential energy
  • Kinetic energy
  • Sound energy
  • Light energy
  • Nuclear energy
  • Chemical energy
  • Thermal energy
• In a phone

  Electrical energy goes in, chemical energy is stored, heat, light and sound energy come out
• With a match

  Chemical energy is stored, kinetic energy is used to strike, heat, light and some sound energy come out
• With fireworks

  Chemical energy is stored, kinetic energy as it moves up, light, heat and sound energy come out, gravitational potential energy as it falls, kinetic energy as it falls back down
• The law of conservation of energy tells us that energy cannot be created or destroyed, it is only transformed into another type of energy
• Kinetic energy

  Equal to 1/2 mass times velocity squared, measured in joules
• Elastic potential energy


  Equal to 1/2 spring constant times extension squared, measured in joules
• Gravitational potential energy

  Equal to mass times gravity times height, measured in joules
• Thermal energy change

  Equal to mass times specific heat capacity times change in temperature, measured in joules
• Power

  Equal to energy transferred over time, measured in watts
• Energy can be wasted, such as heat and sound from a light bulb
• Wasted energy dissipates into the surroundings and spreads out so much it can't be collected and used
• Efficiency


  Equal to useful energy out over total energy in, can be expressed as percentage or decimal
• Renewable energy sources

  • Sun
  • Wind
  • Water (including tidal and hydroelectric)
  • Waves
  • Geothermal
• Non-renewable energy sources


  • Fossil fuels (coal, oil, gas)
  • Nuclear power
• Renewable energy sources

  • Don't release carbon dioxide
  • Inexhaustible
  • Generally non-polluting
• Solar power

  • Doesn't work at night
  • Not very good on cloudy/wintry days
  • Can be expensive to install
• Wind turbines


  • Some people don't like them
  • Don't work well on very windy days
• Tidal and wave power


  • Can be disruptive to local environment
• Hydroelectric power


  • Involves flooding large areas which may include people's homes or animal habitats
• Geothermal power


  • Can only be used in volcanic countries
• Fossil fuels and nuclear power

  • Readily available
  • Cheap source of electricity
  • Coal power stations have short startup time
• Fossil fuels

  • Take millions of years to create, so will run out
  • Heavily polluting, release large amounts of carbon dioxide and other pollutants
• Nuclear power

  • Have to store radioactive waste for long periods
  • Small but potential risk of explosion