Apparatus

Electronic components may be purchased form Maplin, RS or other suppliers.

Activity 1. Start

  • Robot e.g. Climbatron - walks up windows etc
  • Or any electrical toy or gadget which is large enough for the class to see and will catch their interest.

Activity 2. Experiment
Provide a variety of items for the children to use to try to light the lamp bulbs.

If assortments of items are put into bags, then they can be handed round quickly.

If conventional leads and battery holders are not available, the following is a cheap alternative which is quick for the children to connect:

  • Pack of magnetic connectors - bought in a pack of 10 pairs
  • Pack of test leads. These have a crocodile clip at each end
  • MES bulb holders
  • MES bulbs (1.25 V, 250 mA)
  • 1.5 V batteries (avoid alkaline or high power cells)
  • Fishing pole elastic and other insulating cords which resemble insulated wire
  • Crocodile clips

Cut a test lead into two. Bare the cut ends and connect to the bulb holder.

Magnetic connectors can be used to connect the battery into the circuit. These consist of a small magnet attached to a wire and are bought in packs of ten pairs. The magnet can be attached to the battery terminal and the children can attach the wires to the crocodile clips to complete the circuit.

Connect some of the bulb holders to lengths of fishing elastic with crocodile clips and others to lengths of other cords. At first glance the cords should all appear to be insulated wires.

Bag type 1
(Make enough of these for 1 bag between about 4 children because they will be used again in activity 7.)

Circuits which will light the lamp

  • 1.5 V battery
  • Pair of magnetic connectors
  • Bulb
  • Bulb holder with conducting leads and crocodile clips

Bag type 2

Circuits which will not light the lamp

  • 1.5 V battery
  • Pair of magnetic connectors
  • Bulb
  • Bulb holder with insulating ‘leads’ attached and crocodile clips

Bag type 3
Variations on the above two bags with items missing.

Note: The fishing pole elastic looks exactly like insulated wire but children soon notice its elastic properties when the lamp does not light. (Available from fishing tackle shops and useful for demos for other topics).


Activity 5. Circuit game

  • 1 sheet of scrap paper per person
  • A paper hat with a bright lamp on one side and an unlit lamp on the other
  • A paper hat with a picture of a battery on it

If the hats are made with a band fastened by strong paperclips they can be adjusted to fit.


Activity 7.
Experiment Bag type 1 as in activity 2 (a bag between about four children) Collections of everyday articles made of different materials e.g. wire coat-hanger, metal spoon, wooden spoon, plastic spoon, cooking foil, rulers, paper plate, etc. pencil sharpened at both ends 30cm ‘bendy’ pencil with the plastic removed for a length close to each end to expose the core. Similar articles made of different materials help the discussion. Aim to include colourful articles which are quite large. The children can also use their own items.


Activity 8. Demonstration using the ‘sound box’

  • Sound box (instructions - PDF, 241 KB)
  • Samples of materials
  • 30cm bendy pencil and 3m bendy pencil (obtainable from shops selling tricks and gadgets)
  • 1 litre bottle of water (to save having to obtain water before start of session)
  • 2 large transparent plastic beakers
  • Contacts (or probe as in picture)
  • Small pack of salt
  • Stirrer

Activity 11. Demonstration

  • Sound box
  • Thermistor, mounted
  • LDR, mounted
  • LED, mounted

Activity 12. Demonstrations
These circuits are much cheaper, quicker and easier to construct than the sound box they provide examples of semiconductors as sensors.

Circuit

Circuit using a LDR to light a LED when it is dark.

Alternatively, the LED can be replaced by a buzzer so that a noise is made as the LDR is covered or the light intensity falling on it is reduced.

Variations on the circuit can be constructed according to availability of components.

For example the LDR may be replaced by a thermistor to light the LED when it is cold.

In each case adjust the potentiometer so that a small change in the conditions causes the semiconductor device to be switched on or off.

The circuit was wired inside a plastic container so that it was possible to switch on and adjust the potentiometer but children could see only the LDR and buzzer or LED.

Components

  • 6V battery
  • 10 k W potentiometer
  • LDR (e.g. Maplin N59AY)
  • Buzzer (e.g. Maplin KU56L)
  • LED - various

(If it is not possible to construct a ‘sound box’ then these can replace much of activities 8 and 11.)