1. Homework: Presentations for Transfer of Energy on April 24 th.

2. Wasted Energy

3. Energy transfer (change) A lamp turns electrical energy into heat and light energy

4. Sankey Diagram A Sankey diagram helps to show how much light and heat energy is produced

5. Sankey Diagram The thickness of each arrow is drawn to scale to show the amount of energy

6. Sankey Diagram Notice that the total amount of energy before is equal to the total amount of energy after (conservation of energy)

7. Efficiency Although the total energy out is the same, not all of it is useful.

8. Efficiency Efficiency is defined as Efficiency (%) = useful energy outputx 100 total energy input

9. Example Efficiency = 75 x 100 = 15% 500

10. Energy efficient light bulb Efficiency = 75 x 100 = 75% 100

11. Energy efficient light bulb Efficiency = 75 x 100 = 75% 100 That’s much better!

12. More complex examples

13. Read in silence pages 133-136.