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