Efficiency

• What can energy be transferred into?

  Different forms of energy
• Why are most devices not 100% efficient?

  Because energy is lost in the process
• What is the purpose of a lamp?

  To provide light
• How is the output energy of a lamp divided?

  Between light energy and heat energy
• What is considered useful energy output from a lamp?

  Light energy
• How is the efficiency of a device defined?

  Proportion of input energy converted to useful output
• How do you calculate efficiency as a decimal?

  Useful energy output divided by total energy input
• How do you calculate efficiency using power?

  Useful power output divided by total power input
• If a lamp has an input of 300 joules and outputs 45 joules of light, what is its efficiency?

  0.15
• If a lamp has an input of 300 joules and outputs 225 joules of light, what is its efficiency?

  0.75
• How many times more efficient is the LED lamp compared to the incandescent bulb?

  5 times
• 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 states that energy can only be transferred?

  Conservation of energy principle
• If a microwave has an efficiency of 70% and a total power input of 800 watts, what is the useful power output?

  560 watts
• Why are electric heaters considered efficient despite producing waste energy?

  They produce heat as their main function
• What is the equation for calculating efficiency?

  • Efficiency = Useful energy output / Total energy input
  • Efficiency = Useful power output / Total power input
• What are the differences in efficiency between incandescent and LED lamps based on the example given?

  • Incandescent bulb: 45 joules output, 0.15 efficiency
  • LED bulb: 225 joules output, 0.75 efficiency
  • LED is 5 times more efficient
• What are the common mistakes when calculating efficiency?

  • Incorrect division order
  • Resulting in values over 1 or 100%
  • Misinterpretation of energy output