1.2.2 Efficiency of Energy Transfers

• What is efficiency a measure of?

  Energy conversion effectiveness
• Efficiency is calculated as the useful output energy divided by the total input energy and then multiplied by 100%
• In an energy transfer with 75% efficiency, 25% of the energy is dissipated as waste.
• What is the principle of energy conservation?

  Energy cannot be created or destroyed
• Energy dissipation often results in the production of heat or sound
• What are the key points of energy conservation?

  Neither created nor destroyed
• High friction leads to high energy efficiency.

  False
• What is the formula for calculating energy transfer efficiency?

  $\frac{\text{Useful Output Energy}}{\text{Total Input Energy}} \times 100\%$
• If a system has a total input energy of 300 J and a useful output energy of 210 J, its efficiency is 70%
• Order the following examples from highest to lowest efficiency:

  1️⃣ LED Bulbs (90%)

  2️⃣ Energy Star Appliances (80%)

  3️⃣ High-Insulation Homes (75%)

  4️⃣ Hybrid Cars (50%)
• LED bulbs are more energy-efficient than incandescent bulbs.