1. Efficiency

2. (Watts = Joules per second)
Which of these might be the most efficient?
Be prepared to justify your answer!
Slow cooker
Kettle
Electric hob
Period of use?
Energy in?
(Watts = Joules per second)
180 W
2500 W
1500 W
Useful and wasted energy out?

3. Sankey diagrams
These can be used to show energy transfers, and the relative amounts of energy converted to each type of energy

4. Rank these devices in order of efficiency
Draw Sankey diagrams to show the efficiency of the following electrical devices:
Energy in
Energy out
Efficiency?
Light bulb
60W
Light 5W
Heat 55W
Slow cooker
180W
Heat 170W
Light 10W
Mobile phone charger 1W
0.8W Electrical
0.2W Heat
Electric hob
1500W
Heat 1300W
Light 150W
Sound 50W
Kettle
2500W
Heat 2200W
Sound 300W
Rank these devices in order of efficiency

5. Plenary

6. Rank these in order (of efficiency) from your calculations
Were your original guesses right or wrong?
Why were they right/wrong?
Slow cooker
Kettle
Electric hob