1.2

• What is the law of energy conservation?

  Energy cannot be created or destroyed; it can only be transferred into different forms.
• What happens to the total energy of a ball that is kicked, assuming no external forces act?

  The total energy of the system remains constant due to the conservation of energy.
• What is waste energy?

  Waste energy is the energy that is not used by the device for its desired purpose.
• What are the energy changes that occur in a filament light-bulb?

  • Electrical energy is transferred into light and heat energy.
  • Light is a useful energy form, while heat is waste energy.
• What are the two equations to calculate efficiency?

  Efficiency = Useful Output Energy Transfer / Total Input Energy Transfer
• What is another equation to calculate efficiency?

  Efficiency = Useful Power Output / Total Power Output
• How can the efficiency of a system be increased?

  1. Reducing waste output (by lubrication, thermal insulation, etc.)
  2. Recycling waste output (e.g., recycling thermal waste energy as input energy)
• What is the consequence for energy transfer of a material with high thermal conductivity?

  The rate of energy transfer through the material is higher than for a material with lower thermal conductivity.
• Do double-glazed windows have a higher or lower thermal conductivity than single-glazed windows?

  Double-glazed windows have lower thermal conductivity than single-glazed windows.
• What does lower thermal conductivity in double-glazed windows mean for energy transfer?

  It means less energy transfers through them.
• What key factors affect the rate of cooling of a building?

  • The thickness of the walls
  • The thermal conductivity of the walls
• What are three methods of reducing heat loss in a building?

  1. Double glazing
  2. Loft and wall insulation
  3. Thicker walls
• How can the efficiency of a mechanical machine with moving parts be improved?

  By lubricating any moving parts to reduce friction and therefore energy loss due to heating.
• How can the efficiency of a radiator be improved?

  By installing metal foil sheets behind the radiator to reflect heat back into the room.
• How can the efficiency of boiling water in a pan be improved?

  By placing a lid on the pan to reduce heat loss from the top.