energy

• Energy can be stored in different ways

  • Thermal
  • Kinetic
  • Chemical
  • Elastic
  • Magnetic
  • Gravitational
  • Electrostatic
  • Nuclear
• The hotter an object

  The more thermal energy it stores
• Any moving object


  Has a kinetic energy store
• Certain substances


  Release energy through a chemical reaction (e.g. fuels, foods)
• Anything stretched or compressed


  (e.g. plastic band or spring)
• Two magnets that are attracting or repelling

  Have a magnetic energy store
• An object's position within a gravitational field

  Gives it gravitational potential energy
• Two electric charges that are attracting or repelling

  Have an electrostatic energy store
• Nuclear processes


  (e.g. decay, fission or fusion)
• Energy can be changed from one store to another through different energy transfers
• Energy can be transferred

  • Mechanically
  • Electrically
  • By heating
  • By radiation
• A force acts on an object through a distance
• An electric charge moves through a potential difference
• Energy moves from a hotter object to a colder object
• Energy can be transferred by waves (e.g. light, sound)
• Energy, measured in joules (J), cannot be created or destroyed. It can only be transferred from one place to another.
• The energy before a transfer is the same as the total energy after
• Sankey diagram


  Used to show the amount or percentage of energy being transferred
• The sum of the useful and wasted energy equals the energy supplied
• Most energy is dissipated to the surroundings
• Friction between moving parts causes heating and is often the reason for energy being dissipated to the surroundings
• Lubricants


  • Can reduce friction and therefore reduce the amount of energy wasted to the surroundings
  • Insulation can also reduce the amount of energy wasted from a system
• Efficient machines


  Transfer most of their energy into useful forms and do not waste much
• Inefficient machines


  Waste a lot of energy
• To improve the efficiency of a machine you have to reduce the amount of energy that is wasted
• All machines will waste some energy so the efficiency is always below 1 (or 100 %)
• Efficiency = useful energy transferred by device / total energy supplied to device
• Conduction


  Passes energy from particle to particle in solids
• Convection


  Transfers energy through fluids, warmer fluids rise, colder fluids fall and this sets up a convection current
• Radiation


  Can transfer energy through a vacuum. Infrared energy is absorbed and emitted by dark, dull surfaces (and poorly by light, shiny surfaces)
• Gravitational Potential Energy (GPE)


  Energy that is stored due to an object's position within a gravitational field
• Kinetic Energy (KE)


  Energy stored in moving objects
• If you double the mass then the KE will double. If you double the velocity, then the KE will quadruple (x4)
• Non-renewable energy resources


  • Nuclear
  • Gas
  • Oil
  • Coal
• Non-renewable energy resources


  • We currently get most of our energy from them
  • They are slowly running out
  • They produce greenhouse gases and pollution
• Renewable energy resources


  • Solar
  • Wind
  • Hydro-electricity
  • Biofuels
  • Tidal
• Renewable energy resources


  • Do not produce pollution or greenhouse gases
  • Most do not use fuel that can run out
  • Initial costs are high
  • Many are unreliable and do not produce much electricity
• Whilst the use of renewable energy resources is on the rise, we still rely heavily on non-renewable resources
• Renewable energy resources are still expensive and cannot provide enough energy to meet our demands
• Many renewable energy resources are also unreliable, such as wind turbines and solar cells