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?

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

Energy transfer (change) electrical light + heat

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

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

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

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

Efficiency Efficiency is defined as Efficiency (%) = useful energy output x 100 total energy input

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?

Example Efficiency = 75 x 100 = 15% 500

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

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

More complex examples

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