IOP Institute of Physics

Experiments

Electricity Generation Part 1: Magnets and lemons

1. Blow up a balloon and let it go.

Aim/Facts

• We need energy to work and play
 Activity Discussion Ask some of the children to blow up balloons. Burst a balloon and point out that some of the energy used to blow it up has caused the sound of the bang. Point out that all this is tiring.Ask how they feel if they are tired and then have a good meal.Slides 2 and 3See safety note Our energy comes from the food we eat.Food such as sweets have lots of energy in them.

2. Show some mechanical toys, musical instruments, and tools etc

Aim/Facts

• Energy makes things work
 Activity Discussion Slide 4See Apparatus ListSee safety note Keep asking what is needed to make them work. Keep saying ‘Yes that needs energy’.

3. Hold up an electric hairdryer (or other household appliance) and ask what they need to do to make it work.

Aim/Facts

• Lots of things we use around our homes need electricity for them to work
 Activity Discussion Slide 5See safety note Get them to tell you that you need to plug it into the mains.

4. Extra

 Activity Discussion Slide 6Ask them to imagine what we would use if we did not have electricity from the mains. Without electricity our homes would be very different.

5. Explain that electricity is the flow of very, very tiny particles (called electrons).

Aim/Facts

• Electricity is a flow of tiny particles (electrons).
 Activity Discussion Slide 7 Tell them that they can play a game where they are the particles. (Explain the word ‘particles’ as meaning ‘tiny things’.)

6. Game: Arrange the children in a circle.

Aim/Facts

• The electricity carries the energy to where it is needed
• This is very useful
 Activity Discussion Place the large bowl containing dry pasta at one side of the circle. The children walk round the circle and as they pass the bowl they pick up a piece of pasta then keep on moving. As they pass a pan, with a thin up-turned lid, they drop the pasta on the lid so a sound is made.See Apparatus ListSee safety note Explain that the circle represents an electrical circuit. The children represent the particles (electrons) and the pasta represents the energy which is collected by the particles from the power-point. The pan represents an electric bell. The energy is used to make the sound.

7. Circuits

 Activity Discussion Show the animated circuit in Slide 8. Point out that the electrons are all round the circuit before the switch is closed. When the switch is closed the battery is connected across a complete loop of conducting material. Then the electrons move round the circuit as the electricity flows.This is explained in the presentation on Electricity.

8. Hold up a piece of wire 10 cm long and about 1mm thick.

Aim/Facts

• Electrons are very, very, very tiny - far too small for us to be able to see them
 Activity Discussion Explain that there are a huge number of electrons in the piece of wire. There are one hundred billion, billion electrons in the wire.Slide 9Alternatively use the analogies in the Electricity presentation. Ask them for the biggest number they know.There could be a guessing game where they are encouraged keep increasing by millions.Point out that if the same number of small marbles were melted to make a huge marble – it would be bigger than the Earth.Or if we measured the distance to the nearest star in millimetres we would get about same huge number!

9. Circuits: slide 10

Aim/Facts

• If you want to do something useful – you need energy
• Electricity brings energy to where you need it
 Activity Discussion Revise what they know from other activities.Slide 11Reinforce: by using electricity we can make things work just where we want. That the energy flows round wires and is clean – no mess in the house. Point out that the electrons are all round the circuit before the switch is closed. They move round the circuit as the current flows. Then when the switch is opened they are still all round the circuit.You could use the game in the Electricity presentation.

10. Point out that we know why electricity is useful but need to know how it is made.

Aim/Facts

• Batteries or generators make electricity
 Activity Discussion Slide 12

11. Lemon battery demonstration

Aim/Facts

• A chemical reaction occurs which releases energy
• The energy is stored in the battery
• When a battery is connected in a circuit the electrons carry the energy to where it is needed
 Activity Discussion See Apparatus ListHave 4 lemon batteries prepared with a 2p coin and a zinc coated nail in each.Connect a circuit with one lemon. Then try two lemons. Three lemons should light a red LED dimly. Four will light the LED brightly.Slide 13 Explain that a battery needs to have an acid and two different metals dipped in it. The lemon juice is acidic, the coin is copper and the nail is covered with zinc. Other combinations work as well.(Extra- each lemon is a cell. When cells are connected together they are called a battery.)

12. Ask them to tell you when they use batteries and deduce the advantages and disadvantages of batteries.

 Activity Discussion Then show Slide 14 Batteries are portable and cheap.They only store small amounts of energy.

13. Generators work because a moving magnet can cause the electrons to move round the circuit.

Aim/Facts

• Moving a magnet near a wire can generate electricity
 Activity Discussion Slides 15, 16, 17

14. Demonstration of a model generator using a magnet.

Aim/Facts

• Energy used to move the magnet is carried by electrons to where the energy is needed
 Activity Discussion Take the bung from the tube and show the magnet inside. Point out that there is no battery.See Apparatus ListSee safety note on neodymium iron boron magnets

15. Demonstrate a ‘Faraday’ torch. Shake it to show the magnet moving through the coil.

 Activity Discussion Slide 18If available show a ‘wind-up’ torch. Explain that these use new materials which have been developed by scientists and produce very strong magnetic fields.

16. Re-cap

 Activity Discussion Slide 19

17. Bicycle and lamp

 Activity Discussion Prop up the bicycle so that the back wheel is off the floor. Then ask a child to pedal.Slide 20 Ask them why the cycle lamp lights and point out the dynamo. Explain that is works by a magnet moving by a coil of wire.Explain that if the lamp was a traditional 100 watt lamp bulb, then they might just be able to light it. Even a very strong adult working very hard would only be able to light two lamps.

18. Point out that everyday we use lots of electricity.

Aim/Facts

• Scientists are inventing new ways of generating huge amounts electricity
 Activity Discussion Much, much more than just two 100 watt lamp bulbs.This is made by huge generators. These huge generators need huge amounts of energy to produce the electricity.There is a lot more to learn about electricity generation.This will be in Part 2