1.1.14 Efficiency

• Efficiency

  A measure of how well energy or work is converted from one form to another
• Efficiency indicates the proportion of input energy or work that is converted into useful output energy or work
• Efficiency

  • Always a percentage or a ratio
  • Cannot be more than 100%
  • Closer to 100% indicates more effective conversion with minimal waste
• Efficiency Formula (General)

  Efficiency = Useful Output Energy / Total Input Energy × 100%
• Efficiency Formula (Work Done)

  Efficiency = Useful Work Output / Total Work Input × 100%
• Useful Output Energy/Work

  The energy or work that is put to the intended or useful purpose
• Total Input Energy/Work


  The total amount of energy or work supplied to the system
• Efficiency of Incandescent Bulbs

  • If an incandescent bulb converts 60 J of electrical energy into 10 J of light energy, the efficiency is 16.7%
• Efficiency of Car Engine

  • If a car engine uses 5000 J of fuel energy and converts 1500 J into useful kinetic energy for driving, the efficiency is 30%
• Efficiency of Electric Heater

  • If an electric heater consumes 2000 J of electrical energy and 1800 J is converted into heat, the efficiency is 90%
• Wasted Energy

  The energy that is not converted into useful forms and is often dissipated as heat, sound, or light that is not desired
• In a car engine, energy is wasted in the form of heat and friction, reducing overall efficiency
• Improving Efficiency

  • Optimize design of machines and processes
  • Use insulating materials
  • Replace old devices with newer technology
  • Maintain machinery and appliances