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Lesson 2 – Teacher plan – your house2minutes – funky LEDs video play next slide without sound as students enter. Ask what they know about LEDs. Introduce today’s topic and learning objectives5 minutes – video How are LEDs can save the world
5 minutes – Discussion on light bulbs Gather students round and show filament, energy saving and LED light bulbs and why we prefer newer type. Try and draw out efficiency. 10- minutes – efficiency explanation use powerpoint to explain what is efficiency and how to calculate for high ability,30 minutes – Read and do questions OR do experiment I’m not sure if the experiment is possible with our equipment but the next person reading this may know.
5 minutes – extension – how many sensors have you got in or around your home?
How LEDs can change the world!
Learning Objectives
Describe what is meant by efficiency Describe how an LDR and LED work
Calculate efficiency and suggest ways to use an LDR
Keywords
EfficientLight emitting diode LEDLight dependent resistor LDRSensorSensing circuit
Energy and Efficiency
• Be able to list the types of energy
• Be able to describe energy changes in machines
• Be able to calculate efficiency
Types of energy
• Most Kids Hate Learning GCSE Energy NamesMagnetic KineticHeat LightGravitational potential ChemicalSound Electrical Elastic potential Nuclear
Energy transferEnergy transfer diagrams show the locations of energy stores and energy transfers.
How are these different from each other?
electricallight
heat
Efficiency in light bulbs
electricallight
heat
100J
100J
10J
90J
40J
60J
Notice it’s the same energy transfer…but a different amount of
useful energy!
The Efficiency EquationEfficiency = Useful energy transferred ÷ Total energy supplied
This can also be written as: Efficiency = Useful energy transferred Total energy supplied
E.g. a plant takes 100J of light energy and from that stores 30J of chemical energy.
Efficiency = Useful energy Total energy supplied
Efficiency = 30J 100J
Efficiency = 0.33 ALWAYS A DECIMAL, unless you x 100 to get a percentage.
Which light bulb is most efficient?
Light bulb Electrical energy in (J)
Useful energy out (J)
Wasted energy out (J)
A 30 10 20
B 40 15 25
C 50 25 25
Sensors all around you!
A house of the future could have circuits to detect if you are out, if it is daytime, and if the light is on – and then turn it off!
How many things can you think of that use sensors in or around your house? Are any of them LED or LDRs?
Learning Objectives
Describe what is meant by efficiency Describe how an LDR and LED work
Calculate efficiency and suggest ways to use an LDR
Keywords
EfficientLight emitting diode LEDLight dependent resistor LDRSensorSensing circuit