1. Do now!
Can you write in your planners that the energy sheet you stuck in at the end of last lesson is for HOMEWORK due next Wednesday?

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

3. Energy transfer (change)
electrical light + heat

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 output x 100
total energy input

9. Can you copy this (with title) please?
Efficiency
Efficiency is defined as
Efficiency (%) = useful energy output x 100
total energy input
Can you copy this (with title) please?

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

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

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

13. More complex examples

14. Let’s try some questions!
Stick the sheet into your books and answer the questions