1. Write your ideas in the first thought bubble!
Justify why an energy saving light bulb is better for the environment than a regular one
Start of lesson
Write your ideas in the first thought bubble!
Level achieved:
How to improve:

2. Energy efficiency and Sankey diagrams

3. Objectives To draw, and explain energy transfers from, Sankey diagrams
To distinguish between useful and wasted energy transfers
To calculate efficiency of different systems

4. Peer assess your partner’s work and suggest how they could improve
grade
criteria 8
Everything for level 7 plus
Figures for efficiency of a normal vs energy saving light bulb
Several examples of the impact on the environment 7
Detailed explanation of how energy saving light bulbs are more efficient
Diagram is correct and detailed
explanation of the resulting impact of this on the environment 6
how energy saving light bulbs are more efficient
attempted a diagram
description of the resulting impact of this on the environment 5
Short description of how energy saving light bulbs waste less energy than normal light bulbs

5. Present New Information
Whenever energy is transferred, some of it gets wasted. In other words some of the original energy is transferred to an unwanted form.
This can be illustrated using a SANKEY DIAGRAM

6. Sankey Diagram for a Light Bulb
The total energy in = total energy out
What si the useful energy?
What is the wasted energy?
We represent amount of energy using the width of the arrow

7. Sankey Diagram for another Light Bulb
In what way is this bulb different to the first one?

8. Apply to Demonstrate Draw a sankey diagram for the following:
A torch which uses 100J of energy and gives out 20J of light
A car engine takes in 100kJ and gives out 40kJ as kinetic, 40kJ as heat, and 20kJ as sound.

9. Review Sankey diagrams show energy _________
The useful energy goes _______ while the wasted energy goes _____
The _______ of the arrows represent how much _______ is being transferred

10. Present new information
Which light bulb is more efficient? How can you tell?

11. efficiency
Efficiency is a measure of how much energy is useful, versus how much is wasted To calculate efficiency: Efficiency has no units, but can be made into a percentage (multiply answer by 100)
efficiency = useful energy out
total energy in

12. Construct your learning
Around the room there are coloured post-it notes, each describing the energy transfers for the object which they are on.
Your task:
Collect a post-it note
Identify the types of energy and if they are useful or wasted
Draw a sankey diagram of the transfers
Calculate the efficiency of the object
Target level 6a-7c
Target level 7b-7a
Target level 8c

13. Objectives To draw, and explain energy transfers from, Sankey diagrams
To distinguish between useful and wasted energy transfers
To calculate efficiency of different systems

14. Review - Justify why an energy saving light bulb is better for the environment
grade
criteria 8
Everything for level 7 plus
Figures for efficiency of a normal vs energy saving light bulb
Several examples of the impact on the environment 7
Detailed explanation of how energy saving light bulbs are more efficient
Diagram is correct and detailed
explanation of the resulting impact of this on the environment 6
how energy saving light bulbs are more efficient
attempted a diagram
description of the resulting impact of this on the environment 5
Short description of how energy saving light bulbs waste less energy than normal light bulbs

15. Peer assess and justify their grade
criteria 8
Everything for level 7 plus
Figures for efficiency of a normal vs energy saving light bulb
Several examples of the impact on the environment 7
Detailed explanation of how energy saving light bulbs are more efficient
Diagram is correct and detailed
explanation of the resulting impact of this on the environment 6
how energy saving light bulbs are more efficient
attempted a diagram
description of the resulting impact of this on the environment 5
Short description of how energy saving light bulbs waste less energy than normal light bulbs

16. Applying our knowledge
We can calculate the efficiency of any system as long as we can measure the energy inputs and outputs. What will happen if we set up this circuit?

17. Total energy in = Useful energy out = Efficiency = m x C x θ V x I x t
Useful formulae:
V = IR
Electrical power = VI = I2R = V2/R
Electrical energy = Power x Time = VIt = I2Rt = (V2/R)t
Heat energy = mass x specific heat capacity x temperature rise
Total energy in =
Useful energy out =
Efficiency = m x C x θ
V x I x t

18. What do you think will make the most efficient heater?

19. Draw your results table
Change in temperature over ~5 minutes
You will need to also record:
Time
Voltage (average)
Current (average)
Mass of water used
Length and thickness of wire

20. Our experiment Collect your equipment
Do pre-measurements (things that wont change throughout the experiment)
Set up the circuit
Get it checked
Start the experiment!

21. Group results Group Length of wire Thickness of wire
Average temp rise (°C)
Efficiency of the heater 1 2 3 4 5 6 7 8 9 10 11 12

22. Review

23. Plenary What did you learn today? What did you find difficult?
What do you feel most confident in?
How do you feel now?