CONSERVATION AND DISSIPATION OF ENERGY

• What does the law of energy conservation state?

  Energy cannot be created or destroyed
• What happens to the total energy of a kicked ball without external forces?

  The total energy remains constant
• What is waste energy?

  Energy not used for its purpose
• What energy changes occur in a filament light-bulb?

  • Electrical energy is converted to light energy
  • Electrical energy is converted to heat energy
  • Light is useful; heat is waste energy
• What is the equation for efficiency in terms of energy transfer?

  Efficiency = Useful Output Energy / Total Input Energy
• What is the equation for efficiency in terms of power?

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

  1. Reduce waste output (e.g., lubrication)
  2. Recycle waste output (e.g., thermal waste energy)
• What is the consequence of a material with high thermal conductivity?

  Higher rate of energy transfer
• Do double-glazed windows have higher or lower thermal conductivity than single-glazed windows?

  Lower thermal conductivity
• What factors affect the rate of cooling of a building?

  • Thickness of the walls
  • Thermal conductivity of the walls
• What are three methods to reduce 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?

  Lubricate moving parts to reduce friction
• How can the efficiency of a radiator be improved?

  Install metal foil sheets behind the radiator
• How can the efficiency of boiling water in a pan be improved?

  Place a lid on the pan to reduce heat loss