Efficiency

• What is the definition of efficiency?

  Efficiency measures energy wasted versus useful energy transferred
• Why are useful devices considered useful?

  They transfer energy from one store to another
• What happens to input energy in devices?

  Some energy is wasted to useless thermal stores
• How is efficiency calculated?

  Efficiency = useful output energy / total input energy
• How can efficiency be expressed as a percentage?

  Multiply the decimal result by 100
• If a motor has a power input of 250 W and outputs 120 W, what is its efficiency?

  0.48
• What is the maximum efficiency of any device?

  No device is 100% efficient
• Where is wasted energy usually transferred?

  To useless thermal energy stores
• Why are electric heaters considered efficient?

  They are almost 100% efficient in energy transfer
• What happens to energy when using an electric drill?

  All energy eventually ends up in thermal stores
• How can efficiency be improved in devices?

  • Insulating objects
  • Lubricating moving parts
  • Making devices more streamlined
• How does an electric fan waste energy?

  Through friction between the axle and supports
• What is a method to improve the efficiency of an electric fan?

  Lubricating the axle
• What is the significance of improving efficiency in energy transfers?

  • Maximizes energy transferred to useful stores
  • Reduces overall energy consumption by appliances