energy resources

• 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
• How is efficiency calculated in terms of energy?

  Efficiency = useful energy output / total energy input
• How is efficiency calculated in terms of power?

  Efficiency = useful power output / total power input
• If a lamp has an input of 300 joules, what is the useful energy output for an incandescent bulb that converts 45 joules?

  45 joules
• If a lamp has an input of 300 joules, what is the useful energy output for an LED bulb that converts 225 joules?

  225 joules
• How do you calculate the efficiency of the incandescent bulb?

  Efficiency = 45 joules / 300 joules
• How do you calculate the efficiency of the LED bulb?

  Efficiency = 225 joules / 300 joules
• How many times more efficient is the LED lamp compared to the incandescent bulb?

  5 times more efficient
• How do you convert efficiency figures into percentage terms?

  Multiply by 100
• What is a common mistake when calculating efficiency?

  Getting the division the wrong way around
• What happens if you calculate efficiency incorrectly?

  You get a value greater than one or 100%
• What does an efficiency rating of 1.33 or 133% imply?

  More energy out than input
• What principle states that energy can only be transferred?

  Conservation of energy principle
• If a microwave is 70% efficient with a total power input of 800 watts, what is the useful power output?

  560 watts
• How do you convert efficiency from percentage to decimal?

  Divide by 100
• What is the relationship between waste energy and useful output in heating devices?

  • Heating devices produce thermal energy as output
  • Thermal energy is not considered waste
  • It counts as useful output
• What is the maximum efficiency of any device?

  Less than 100%