energy stores and systems

• Energy store


  The capacity for doing work
• Types of energy store

  • Magnetic
  • Internal (thermal)
  • Chemical
  • Kinetic
  • Electrostatic
  • Elastic potential
  • Gravitational potential
  • Nuclear
• Magnetic energy store


  • The energy stored when repelling poles have been pushed closer together or when attracting poles have been pulled further apart
• Magnetic energy store


  • Fridge magnets
  • Compasses
  • Maglev trains which use magnetic levitation
• Internal (thermal) energy store

  • The total kinetic and potential energy of the particles in an object, in most cases this is the vibrations - also known as the kinetic energy - of particles. In hotter objects, the particles have more internal energy and vibrate faster
• Internal (thermal) energy store

  • Human bodies
  • Hot coffees
  • Stoves or hobs
  • Ice particles vibrate slower, but still have energy
• Chemical energy store


  • The energy stored in chemical bonds, such as those between molecules
• Chemical energy store


  • Foods
  • Muscles
  • Electrical cells
• Kinetic energy store


  • The energy of a moving object
• Kinetic energy store


  • Runners
  • Buses
  • Comets
• Electrostatic energy store


  • The energy stored when repelling charges have been moved closer together or when attracting charges have been pulled further apart
• Electrostatic energy store


  • Thunderclouds
  • Van De Graaff generators
• Elastic potential energy store


  • The energy stored when an object is stretched or squashed
• Gravitational potential energy store


  • The energy of an object at height
• Gravitational potential energy store

  • Aeroplanes
  • Kites
  • Mugs on a table
• Nuclear energy store


  • The energy stored in the nucleus of an atom
• Energy store


  The different ways in which energy can be stored, including chemical, kinetic, gravitational potential, elastic potential and thermal stores
• Energy transfer


  The different ways in which energy can be transferred from one store to another includes heating, by waves, electric current or by a force moving an object
• Energy can be described as being in different 'stores'. It cannot be created or destroyed but it can be transferred, dissipated or stored in different ways
• Energy transfers are going on all the time - whenever a system changes there is a change in the way some or all of the energy is stored
• Examples of energy transfers

  • Mechanical work - a force moving an object through a distance
  • Electrical work - charges moving due to a potential difference
  • Heating - due to temperature difference caused electrically or by chemical reaction
  • Radiation - energy transferred as a wave, eg light and infrared
• Doing 'work'


  The scientific way of saying that energy has been transferred
• Transfer diagrams


  • The boxes show the energy stores and the arrows show the energy transfers
• Sankey diagrams


  • Start off as one arrow that splits into two or more points, showing how all of the energy in a system is transferred into different stores. The width of the arrow is drawn to scale to show the amount of energy
• Energy store


  The capacity for doing work
• Energy cannot be created or destroyed but it can be transferred, dissipated or stored in different ways
• Energy dissipation


  The spreading out and transfer of energy stores into less useful forms, such as thermal energy causing the surroundings to heat up
• Dissipated energy is often referred to as 'wasted' energy, since it is not transferred to a useful output
• Examples of energy dissipation

  • Electrical cables warming up
  • Two surfaces rubbing together causing heating
• Friction


  A force that opposes or prevents movement and converts kinetic energy into heat
• Lubricant


  Anything which reduces the friction between two surfaces
• Examples of reducing energy dissipation

  • Using LED light bulbs instead of filament lamps
  • Adding lubricant between surfaces
• Electrical work


  Energy transferred by an electric current
• Examples of energy dissipation in different systems

  • Radio/speakers: electrical work transferred into sound waves and infrared radiation
  • Tumble dryer: electrical work transferred into thermal energy to dry clothes
• No system is perfect, whenever there is a change in a system, energy is dissipated