ENERGY STORES AND SYSTEMS

• Energy is never created or destroyed, it's only ever transferred between different forms and objects
• Forms of energy


  • Thermal or internal energy
  • Kinetic energy
  • Gravitational potential energy
  • Elastic potential energy
  • Chemical energy
  • Magnetic energy
  • Electrostatic energy
  • Nuclear energy
• Energy in each of these stores isn't fixed, it can be transferred from one to another
• Energy transfer


  1. Mechanically

  2. Electrically

  3. By heating

  4. By radiation like light or sound waves
• System


  The collection of matter that we are considering
• Open system


  The system can exchange energy with the outside world
• Closed system


  The system is separate from the outside world, so neither matter nor energy can enter or leave
• Energy transfer in a kettle


  1. Electrical energy from the plug socket flows to the heating element

  2. Heating element transfers energy to the water's thermal energy store
• Work done


  Another way of saying energy transferred
• Types of work done

  • Mechanical
  • Electrical
• Mechanical work done


  Using a force to move an object, e.g. kicking a ball
• Electrical work done


  Energy required to overcome resistance in wires of a circuit
• Friction slowing down a train


  Friction does work, causing energy in the wheel's kinetic energy stores to be transferred to the thermal energy stores of the surroundings