Electricity robots and electric eels

Electricity
Robots and electric eels
Supports National Curriculum, Key Stage2, Units 2F, 4F and 6G
Suitable for years 4,5 and 6.
The time for whole session is about 1 ½ hours. This can be varied by taking shorter paths through the
material. Choices may depend on the apparatus available or the particular needs of the class.
Outline of content
Aims to
- establish what the children already know, using demos and class experiments
- investigate simple circuits through class experiments and deduce rules for a current to flow.
- provide a clear analogy of conduction and electric circuits through a game
- show some materials are conductors and others are insulators through class experiments
- investigate the conductivity of materials including water and semi-conductors using a ‗sound
box‘
- provide guidance for safe use of electrical appliances in the home
- show that some materials can change their conductivity and explore uses
- demonstrate and discuss up-to-date applications by linking the children‘s knowledge with
their experience.
Points to note:
Please read the notes the safety notes at end of this document.
Cross References
- The slides in the PowerPoint presentation are referenced in the table and have
commentary notes.
- As the presentation may be running throughout the session some simple slides provide a
suitable background, alternatively switch to a black screen.
- Apparatus details are below the table and are linked to the relevant sections.
- Notes about safety are below the table
Vocabulary
The presentation uses expressions included in the KS1&2 strategies.
Are you looking for Electric Organizer Bags
Misconceptions which are to be corrected
- When a circuit is completed, the current (electrons or particles carrying charge) pours out of
the battery and round the circuit.
- When the current stops flowing the electrons all go back into the battery.
- Materials are either very good conductors or very good insulators.
- It is safe to operate mains switches with wet hands.
- The physics that they learn is not relevant to their everyday lives.
I found that the children had lots of ideas to contribute and were fascinated. I therefore allowed the
discussions continue and answered numerous questions so that the sessions took whole afternoons.
Teachers, in each school, commented that the whole group was interested and took part fully. The
schools which were visited had very different characters and the total ability range was very wide.

Electricity : Robots and electric eels
Activity Discussion Aims/facts
1. Start by attracting the children’s
interest.
(Show Powerpoint Slide 1)
Show a toy robot e.g. one that can
climb windows or smooth surfaces
and has a flashing lamp.
Ask them how the robot can climb the
window.
Some may correctly say it has suckers
on its feet. If they start from this point
ask how it moves and then how
upwards. Encourage answers including-
electricity, battery, motors, circuits, lamp
----
Use the demo to find out
what they know and to
establish that they
understand that the
robot will not work
without the battery.
2. Experiment
Give out, one between four, bags with
assorted contents as listed.
See Apparatus List
Some will have components to make
a complete circuit- others will not. As
you hand them out explain that some
of the groups may not be able to light
the bulbs.
After this collect all apparatus in the
original bags.
View Safety Notes
Encourage the children to discuss the
components and ‗wires‘ used to connect
up the ‗circuits‘ and whether they allow
electric currents to flow. They should
Also encourage statements such as
―our circuit does not work because it
does not have a -- ‖
To light a lamp a battery
and a complete path
(called a circuit) made of
conducting material are
needed.
Note: this activity may
be revision.
3. Forest analogy
Show Powerpoint Slides 2 to 6
From high above a forest, the trees
look like an almost smooth surface,
from lower down the trees are seen
and from even lower monkeys can be
seen which move between the trees.
Ask the children to think about what is
happening in a metal.
Explain that there are spaces in the
metals (like between the trees) that
very, very tiny particles can move
through.
Help them to visualise how small the
particles are by discussing huge
numbers. They may suggest a million.
Clarify that they understand this is 1000
lots of 1000--- about the number of
people on Merseyside or in a city near
them.
Tiny particles (electrons)
move round a circuit
when a current flows.
4. Thought experiment to try to
imagine the size of an electron.
Image a pin head. Then talk about
each of a million people putting one
tiny dot along a line on the pin head.
Explain that it is very difficult to image
such tiny dots but they are far, far
larger than the particles moving
through the wires. Even if a million
dots are put on one of these tiny dots,
they would be much larger than an
electron.
Explain that the particles moving round
the circuit are called electrons.
Encourage the children to discuss the
problems of imagining such large
numbers and such tiny dots and explain
that everyone has this problem – they
are far too small to see. Link back to the
idea that from an aeroplane they would
be unable to see the monkeys moving
between the forest trees.
The electrons are VERY,
VERY tiny.
5. Circuit game
See Apparatus List
Show Powerpoint Slide 7
Give every child a piece of scrap
paper and ask them to crush it into a
small ball.
Ask them all to stand in a large circle.
(It is best to arrange where this will be
before the session.)
Point out that every child has a ball at
the start. The balls do not all start in one
place. When you say ‗stop‘ each should
still have a ball. Some practice is
usually needed and enjoyed. Once they
can do this, discuss what is needed to
start the electrons moving round the
circuit.
Whether the current is
flowing or not, the
electrons are all around
the circuit.
Reinforce that a
complete loop is needed
for the electrons to flow.
When a current flows the
electrons move round

Every child should hold the paper ball
in their left hand. On the count of ‗1‘
each child should take the ball in their
right hand and on the count of ‗2‘ put
it in the left hand of the child next to
them. This is repeated as you say
121212--- until you say ‗stop‘.
Put a paper hat on showing a battery.
Put the ‗lamp hat‘ on a child. Also
arrange that the teacher will shout
―stop!‖ after the ‗current‘ has been
flowing for a while.
(upper size of children in ring is about
20 - others could watch)
You represent the battery because you
are saying 121212—so that the current
flows. The teacher is a switch – which
will need discussion.
The child with the lamp-hat (or another
child standing behind) should rotate it to
show the unlit lamp when the current
stops flowing.
Powerpoint Slide 8
the circuit and the lamp
lights.
A switch can be used to
break the circuit so that
the current stops and the
lamp goes out. The
electrons do not all rush
back to the battery.
(Be careful not to imply
that the electrons stop
moving completely.)
6. Drawing circuits
(If required )
Show Powerpoint Slides 9 and 10
Discuss the problem of drawing pictures
to represent the components.
Symbols do not need labelling and are
easier to draw.
Simple circuit diagrams
7. Experiment
See Apparatus List
To each group of 4 children, hand out
a bag of components which form a
circuit to light a lamp.
Also hand out a collection of items
made of different materials.
Ask the children to complete the
circuit to light the lamp and then
disconnect the circuit at one point and
connect in an item made of a material
to be investigated.
View Safety Notes
Discuss which items are good
conductors.
Discuss the materials the items are
made of.
Point out that the lamp is not bright in
some cases- eg with the bendy pencil.
(A sheet could be given to each group
to record their results but with young
children a discussion works well.)
Metals are good
conductors, most other
materials are insulators
(materials which do not
allow electricity to flow
through them).
Some materials allow
electric currents to flow
through them and are
not metals (e.g. the
pencil bendy pencil -
carbon)
8. Demonstration using the ‘sound
box’.
See Apparatus List
and the pdf of assembly and
operating instructions for the sound
box.
Show that better the conductor the
higher the pitch. Reinforce this using
the demo buttons on the sound box.
Text a good selection of materials
including both a 30cm and a 3m
bendy pencil.
Show that water is a conductor and
when salt is added the pitch is raised.
Explain that people conduct
electricity. People work by tiny
currents flowing round their bodies.
(Show Powerpoint Slide 12)
Hold a contact of the sound box in
each hand and listen to the note.
Then increase the grip on each
contact, then dampen fingers and grip
Discussion about the frequencies of the
sounds heard. Encourage them to
explain what they understand from the
sounds heard. Link with their music
knowledge if appropriate.
Discuss the sounds heard in each case.
Ask a different child to help with each
activity.
Ask for a volunteer to test if people
conduct electric currents.
Voltage can be described as an
electrical ‗push‘ but only mention it if
necessary.
Some good conductors
are better conductors
than others.
Water is a conductor.
Salty water is a better
conductor than tap
water.
People conduct
electricity—wet hands
cause a better contact.

the contacts.
Point out that the ‗sound box‘ has
batteries (3V) in it so it is safe to touch
the contacts.
9. Electric eel
These give their prey an electric
shock to stun them. Show
Powerpoint Slide 14
They live in water that is a conductor.
Discuss electric eels seen at large
aquaria. Ask if they remember the eel
causing lights to flash.
(Note: the electric eel is a fish, not a
true eel, found in the Amazon River
Basin, South America)
Lead into the idea that
electricity can be
dangerous.
10. Mains electricity is dangerous.
Show Powerpoint Slide 15 to 20
Show slides indicating that wet hands
made good electrical contact.
Explain that during class experiments
batteries are used.
Show pictures of bathroom light cord.
Discuss why we do not have wall
mounted light switches and sockets in
the bathroom.
They enjoy this but it is probably better
to keep the discussion away from horror
stories which they will relate.
Safety warnings -
We conduct electric
currents which can harm
us.
NEVER handle electrical
appliances with wet
hands.
NEVER play with mains
electricity
Use low voltage
batteries in class
experiments.
11. Demonstration using the
‘sound box’.
See Apparatus List
and the pdf of assembly and
operating instructions for the sound
box.
a) with LDR- show effect of
covering and uncovering the
LDR
b) with thermistor- show effect of
warming the LDR
c) with LED- show effect of
reversing the contacts
View Safety Notes
Discuss the change in properties and
the conditions change.
Some materials are
neither good conductors
nor bad conductors
(insulators).
These are
‗semiconductors‘.
Point out that there is a
lot more to learn.
12. Demonstration
See Apparatus List
a) using a circuit with LDR and a
LED show that the changes in
illumination causes changes in
conduction properties which can
be used as a switch to switch the
LED on or off.
b) variations are possible in the
combinations of components
according to availability. The
circuit above with a buzzer instead
of the LED works well. Adjust the
potentiometer so that in full room
light the buzzer is silent. As soon
as the circuit was in partial shade
the buzzer started to sound. When
it was covered it sounded loudly.
c) using circuit with thermistor and
buzzer show that the changes in
Discuss possible uses.
Children enjoy thinking out uses for
sensors.
Examples that may be suggested in
discussion.
a) a freezer high temperature
warning
b) automatic porch lights and
street lamps. (Powerpoint Slide
22)
c) They will ask about other uses
and suggest ideas. (Powerpoint
Slide 23)
d) They ask about LEDS because
they are used in so many
devices as indicators.
(Powerpoint Slide 24)
e) The discussion here will
Materials with interesting
conduction properties
are used for numerous
useful applications.

conduction properties can be used
as a switch to switch the buzzer
on and off.
View Safety Notes
probably open up into an Q/A
session with lots of ideas being
proposed- using sensors.
13. Applications
Finally show slide of traffic lights
which use LEDs and suggest they
look out for them.
Explain that the development of LEDs
for traffic lights is recent and they last
longer and save money ---
(When one LED fails the signal
continues to function. The signals need
replacing much less frequently and
even 100 LEDs draw less current than a
big filament lamp so saving money.)
Or lead into another example of an up-
to-date application that they can
understand.
Scientists are finding out
new facts continuously
and these are used to
develop new ideas.
14. Re-cap
15. Ending
Explain that semi-conductor materials
are used in lots of devices
they enjoy using.
Computers, Mobile phone, Sound
systems, TV, Electric guitars----
Being a scientist is
exciting and
interesting.
Investigation
If necessary, the ending could be
modified to lead into an investigation.

List of apparatus
Electronic components may be purchased form Maplin, RS or other suppliers
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.
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
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
NB 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)
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.

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.
8. Demonstration using the ‗sound box’
 Sound box 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
11. Demonstration
 Sound Box
 Thermistor, mounted
 LDR, mounted
 LED, mounted
12. Demonstrations
These circuits are much cheaper, quicker and easier to construct than the sound box they provide
examples of semiconductors as sensors.

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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.)
Safety notes
Possible hazards to be discussed with the teacher BEFORE the visit:
 a child short-circuiting a battery so it or a wire becomes hot – the risk of harm is reduced by
the choice of cell type. Avoid alkaline or high power cells.
 a child catching a finger on a crocodile clip - use the miniature ones with plastic covers which
cannot open very far.
 A child swallowing a button magnet - check that the magnets in the magnetic connectors (if
used) are securely in place before use.
 Injury from items to test for conductivity – check that they are not sharp (eg a wire coat-
hanger hook should be bent round or taped)
 The 'sound box' and other electronic circuits must be constructed so that they do not present
a hazard if they are handled by the children.

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