physics

• Different kinds of energy stores

  • Chemical energy
  • Kinetic energy
  • Gravitational potential energy
  • Elastic potential energy
  • Thermal (Heat) energy
  • Nuclear store
  • Magnetic
  • Vibrational
• Light, electrical (as in a current) or sound are not energy stores. These are active processes and cannot be stored in a stable state.
• Electricity is a flow of charge that transfers energy from one energy store to another.
• Dissipation


  Energy becoming spread out to the stores of surrounding objects (usually wasted thermal energy)
• Lubrication


  A method of reducing unwanted energy transfers by application of a lubricant (e.g. oil) to reduce friction
• Insulation


  A method of reducing energy transfers by the use of insulators
• Conservation of energy


  The law that states that energy cannot be created or destroyed
• Closed system


  An isolated system in which no energy transfers take place out of or into the energy stores of the system
• Work


  Work is done on an object when a force makes the object move
• System


  Object or group of objects
• Friction


  A contact force resisting the relative motion between two surfaces. Friction in machines always causes energy to be wasted
• Input energy


  Energy supplied to a device
• Useful energy


  Energy transferred to where it is wanted in the way it is needed
• Wasted energy


  Energy that is not usefully transferred
• Efficiency of a device

  The proportion of the total input energy that is transferred in useful ways
• A Coal fire


  Energy is shifted from a chemical store (fuel) to a thermal store
• Bow & arrow


  Elastic potential energy kinetic and thermal energy
• Placing a book on a shelf

  Energy is shifted from the chemical store of your arm to the gravitational store of the book
• Apple falling from a tree

  Gravitational potential energy decreases, kinetic energy increases, then kinetic energy is transferred into thermal and sound energy
• Methods of energy transfer (also known as energy carriers)


  • Mechanical
  • Electrical
  • Radiation
  • Heating
• Why devices waste energy

  • Friction between moving parts causes heating
  • Resistance of a wire causes wire to get hot when current passes through
  • Air resistance causes force on a vehicle that opposes its motion
  • Working machinery creates sound
• How to reduce energy wastage

  • Lubrication of moving parts reduces friction
  • Use wires with as little resistance as possible
  • Streamline the shape of the vehicle to reduce air resistance
  • Tighten loose parts to reduce vibration and noise
• Energy transfer in a pumped storage power station

  1. Water from the high level reservoir flows into the low level reservoir, generating electricity as the water turns the turbine connected to the generator

  2. The generator produces some sound, which is wasted energy