Using Energy

• What is meant by the conservation of energy?

  The total amount of energy in a closed system remains constant, energy cannot be created or destroyed but can change from one form to another.
• Energy changes in a filament lightbulb

  Electrical energy is transferred into light and heat energy.
• What is waste energy?

  The energy that is not used by the device for its desired purpose, or not converted into the desired form.
• Efficiency =

  Useful output energy or power / total input of energy or power
• Consequence for energy transfer of a material with a high thermal conductivity


  The rate of energy transfer through a material is higher than for a material with low thermal conductivity.
• Three methods of reducing heat loss in a buidling

  Double glazing, loft and wall insulation, thicker walls
• How can unwanted energy transfer in a mechanic system be reduced?

  Lubrication to reduce friction
• How can the efficiency of a system be increased?

  Reducing waste output (by lubrication, thermal insulation etc.) or by recycling waste output (e.g. recycling thermal energy as input energy).