Energy Efficiency

• What can energy be transferred into?

  Different forms
• Why is energy not always transferred into the intended form?

  Devices aren't 100% efficient
• What is efficiency in terms of energy output?

  • Proportion of input energy converted to useful output
  • Useful energy output is considered light energy
  • Waste energy is considered heat energy
• What is the formula for calculating efficiency?

  Efficiency = useful energy output / total energy input
• How can efficiency be calculated using power?

  Efficiency = useful power output / total power input
• How do you convert efficiency from decimal to percentage?

  Multiply by 100
• What happens if you calculate efficiency incorrectly?

  You may get a value over 1 or 100%
• What does an efficiency rating over 100% imply?

  More energy output than input
• What principle explains why energy cannot be created or destroyed?

  Conservation of energy principle
• Why are most devices not 100% efficient?

  • All devices produce some waste energy
  • Most often in the form of thermal energy
  • Some devices are designed to produce heat as useful output
• What is the useful output of an electric heater?

  Thermal energy
• What is the purpose of a lamp?

  To provide light
• What is considered waste energy in a lamp?

  Heat energy
• What are the differences between useful energy output and waste energy output?

  • Useful energy output: Light energy from a lamp
  • Waste energy output: Heat energy from a lamp