P1.2

• Closed system


  A system in which no energy transfers takes place out of or into the energy stores of the system
• Energy can be transferred between energy stores within a closed system. The total energy of the system is always the same before and after any such transfers.
• Open system


  Energy can go in and out
• System


  An object or group of objects
• Dissipation


  Energy is being wasted
• vacuum (e.g. space)


  an example of a close system because energy cannot be transferred in or out
• Pendulum energy transfer description 


  as it swings up, kinetic energy decreases and gravitational potential energy increases. At the top no kinetic energy + a large amount of gravitational potential energy

  
• Law of conservation of energy


  States that energy is never created or destroyed; it is only transferred from one store to another
• Conservation of energy principle


  Energy can be transferred, usefully stored or dissipated, but can never be created or destroyed
• Energy can only move between different objects and different forms
• Charging a phone

  1. Electrical energy from main supply travels along wire

  2. Transferred to chemical energy store in phone's battery
• Using a phone


  1. Chemical energy converted to electrical energy

  2. Electrical energy flows around circuit

  3. Powers screen and speaker
• Energy transfer in phone

  1. Electrical energy converted to light energy in screen

  2. Electrical energy converted to sound energy in speaker
• Energy transfer

  Some energy is dissipated as wasted energy, generally in the form of heat
• System


  A portion of the physical universe that is chosen to analyze, everything outside is the environment
• Open system


  • Energy and matter can freely move between the system and the environment
• Closed system


  • Energy and matter can't enter or escape the system
• Phone in sealed jar (closed system)

  Heat energy from phone dissipated to air inside jar, stays within the system
• The overall energy of a closed system doesn't ever change