efficiency

• What does energy efficiency measure?

  The proportion of energy that is wasted
• Why is it important to reduce the rate at which energy is wasted?

  To save energy and improve efficiency
• What is energy dissipation?

  • Transfer of energy into less useful forms
  • Often referred to as 'wasted' energy
  • Causes surroundings to heat up
• What causes a rise in temperature in a system?

  The transfer of wasteful energy
• How is energy dissipated in a mechanical system?

  When two surfaces rub together
• What does friction do in a mechanical system?

  Opposes movement and converts kinetic energy
• What happens to the internal energy of surfaces due to friction?

  It increases due to heating
• What are the useful and wasted energies of an electric kettle?

  • Useful energy: Heats the water
  • Wasted energy: Internal energy heating the kettle, infrared radiation to surroundings
• What are the useful and wasted energies of a hairdryer?

  • Useful energy: Heats the air, kinetic energy of the fan
  • Wasted energy: Sound radiation, internal energy heating the hairdryer, infrared radiation to surroundings
• What are the useful and wasted energies of a lightbulb?

  • Useful energy: Light radiation from the filament
  • Wasted energy: Infrared radiation to surroundings
• What are the useful and wasted energies of a TV?

  • Useful energy: Light radiation for images, sound radiation for audio
  • Wasted energy: Internal energy heating the TV, infrared radiation to surroundings
• How can devices reduce energy dissipation?

  By using lubrication to reduce friction
• What is thermal insulation used for?

  To reduce wasteful thermal energy dissipation
• What material is often used for thermal insulation in kettles?


  Plastic
• What are the key concepts related to energy dissipation and efficiency?

  • Energy efficiency measures wasted energy
  • Energy dissipation refers to energy loss
  • Friction converts kinetic energy to heat
  • Insulation reduces thermal energy loss