energy transfers

• System


  An object or group of objects

  
• Closed system


  A system in which there is no net change to the total energy

  
• Law of conservation of energy

  Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed

  
• Useful energy transfer


  When energy is transferred by a device to energy stores we want
• Wasted energy transfer


  When energy is transferred by a device to energy stores we don't want
• Dissipate


  When energy spreads out and is transferred to energy stores into less useful forms
• Dissipated energy


  Energy which is wasted and is usually transferred to the surroundings, causing them to heat up
• Lubricate


  When a substance is used to reduce wasted energy transfers by reducing the friction between moving parts

  
• Insulate


  When a substance is used to reduce wasted energy transfers by reducing the amount of heat that is transferred to the surroundings

  
• Thermal conductor


  A material that allows charge or heat to pass through it easily

  
• Thermal insulator


  A material that does not allow charge or heat to pass through it easily

  
• Thermal conductivity


  The rate of energy transfer by conduction through a material

  
• Conduction


  When heat is transferred through a material due to vibrating particles colliding and transferring energy from one particle to another

  
• Convection


  When heat is transferred through a moving liquid or gas due to differences in densities

  
• Radiation


  When heat is transferred from a hot object due to the object emitting infrared (heat) radiation