conservation of energy

• 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 the main supply travels along the wire

  2. Gets transferred to the chemical energy store in the phone's battery
• Using a phone


  1. Chemical energy is converted back to electrical energy

  2. Electrical energy flows around the circuit

  3. Powers the different parts like the screen and speaker
• Energy transfer in the screen

  Electrical energy is converted to light energy
• Energy transfer in the speaker

  Electrical energy is converted to sound energy
• Some energy is dissipated as wasted energy, generally in the form of heat
• Open system


  A portion of the physical universe that you've chosen to analyze, where energy and matter can freely move between the system and the environment
• Closed system


  The entire contents of a sealed jar, including the phone and the air within, where energy and matter can't enter or escape
• In a closed system, the overall energy doesn't ever change