1. What is Energy?

2. “The capacity to do work” Not a very good definition!

3. Types of energy Energy can take many forms;

4. Light

5. Sound

6. Kinetic (movement)

7. Electric

8. Chemical

9. Gravitational potential

10. Nuclear

11. Types of Energy HeatChemical LightGravitational SoundElastic/strain KineticNuclear Electric

12. Types of Energy HeatChemical LightGravitational SoundElastic/strain KineticNuclear Electric Stored/potential

13. The Law of Conservation of Energy

14. Energy can be changed (transformed) from one type to another, but it can never be made or destroyed.

15. This means that the total amount of energy in the Universe stays the same!

16. Energy Flow diagrams We can write energy flow diagrams to show the energy changes that occur in a given situation. For example, when a car brakes, its kinetic energy is transformed into heat energy in the brakes. Kineticheat sound

17. Other examples When a rocket launches.

18. Other examples When a rocket launches. Chemicalkinetic gravitational sound heat

19. Energy degradation! In any process that involves energy transformations, the energy that is transferred to the surroundings (thermal energy) is no longer available to perform useful work.

20. Energy Circus Around the room are 12 examples of energy changes (some simple, some a little more complicated!) For each example I want you to write the name of the apparatus and the energy flow diagram for that experiment (including heat losses) You will move to the next experiment at the appropriate signal.

21. Ready?

22. Go!

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

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

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

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

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

28. Efficiency Efficiency is defined as Efficiency = useful energy output total energy input

29. Example Efficiency = 75 = 0.15 500

30. Energy efficient light bulb Efficiency = 75 = 0.75 100

31. Energy efficient light bulb Efficiency = 75 = 0.75 100 That’s much better!

32. More complex examples