6 Electricity

6.1 Which materials conduct

electricity?
We are going to…
• use a fair test to group objects into conductors and insulators of electricity
• identify risks and carry out practical work safely
• make predictions and identify if results support predictions or do not
support predictions
• describe simple patterns in results and make a conclusion from results.

– 4 + 1

Getting started
1 Name the components of the circuit numbered 1, 2, 3 and 4 .
2 What is the function of the component 4?
3 Why does the lamp light up in this circuit?
conductor insulator

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 6.1 Which materials conduct electricity?

Conductors and insulators

A material that allows electricity to pass through it is called a conductor.
A material that does not allow electricity to pass through it is called an insulator.
In the next investigation you are going to test different materials to see whether
they are conductors or insulators.

Think like a scientist

Test which materials conduct electricity

You will need:

one piece of plastic-covered wire with a crocodile clip on one end,
a screwdriver, a 1.5 V cell in a cell holder with a crocodile clip on the end of one
of the wires, a 1.5 V lamp in a lamp holder, objects made of different materials

Before you begin, make sure you follow safety rules:

• If you have to cut the plastic off the ends of the wires, use a wire stripper.
Grip the wire in your left hand and strip off the plastic away from you.
• When the circuit is complete, do not touch any bare electric wires.
Always hold the plastic covered wire.
Questions
1 Why is it important to cut away from you?
– +
2 How can you strip the plastic off the wires safely?
3 Why must you not touch bare wires when the
circuit is complete?
Step 1
• Attach the end of wire from the cell holder which
doesn’t have a crocodile clip to one side of the
lamp holder.
• Use the screwdriver to loosen the screw of lamp
holder and then tighten it after you have wound the
wire around. Use tape to attach wires to the cell.
Attach the separate piece of wire to the other side
of the lamp holder. Again, attach the end which
doesn’t have a crocodile clip to the lamp.

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 6 Electricity

Continued

Step 2
• Check that your circuit works.
Hold the wires and clips where
they are covered in plastic. Allow
the crocodile clips to touch.
• If the lamp lights up, the circuit
is complete. If the lamp does
not light up there is a break in
the circuit. Check that you have
connected the wires properly.
• If you separate the crocodile clips, you break the circuit and
the lamp goes out. This is your testing equipment. You will
use the same testing equipment to see which materials
allow electricity to pass through.
• Before you begin, predict which materials will allow electricity to
pass through and which will not. Record your predictions in a table
like the one below. Place a tick ✓ in the 2nd or 3rd column.

Prediction Result

Material conductor insulator conductor insulator

Step 3
• Test each material. Hold one crocodile clip at one end of the object.
Hold the second crocodile clip at the other end of the object.
• If the lamp does not light up you can try again to make sure.
• Record your results by placing ticks ✓ in the last two columns of your table.

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 6.1 Which materials conduct electricity?

Continued
Questions
4 How well did your results support your predictions?
5 How did you make sure that the test was fair?
6 Identify a pattern of which types of material are
conductors and which are insulators.
7 Did any materials not fit this pattern? If so,
identify the material.
8 What conclusion can you make from your results?
9 Which two types of scientific enquiry have you
practised in this activity?
10 Why are lightning conductors made from copper?

How am I doing?
How many stars ( , or ) would you give yourself for these skills?
• Can I identify and describe a pattern in results?
• Can I make a conclusion from results that answer the question?

What have you learnt about working safely with electricity?

Look what I can do!

I can predict which materials will be conductors and insulators of electricity.
I can use a circuit to make a fair test to group materials into conductors
and insulators of electricity and test my predictions.
I can know the risks and work safely doing practical work.
I can identify a pattern in results.
I can make a conclusion from results.

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 6 Electricity

6.2 Does water conduct electricity?

We are going to…
• investigate if water conducts electricity
• identify and explain risks and carry out practical work safely
• make predictions and identify if results support predictions or do not support
predictions
• make a conclusion from results
• identify the risks and carry out practical work safely. distilled water
pure water

Getting started
1 If we put salt into water and stir it, what
happens to the salt?
2 How can we test to see if a material conducts
electricity or not?

Is water pure?
Water from a river or the tap is not pure water.
It has salts dissolved in it. Distilled water is
pure water. Distilled water is water that has
been boiled and the steam has
been allowed to cool down to
form liquid water again. This
water is distilled water and
contains no salts.
All living things contain water.
Our bodies are about 65% water!
This water has salts dissolved
in it so it is not pure.

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 6.2 Does water conduct electricity?

Think like a scientist

Investigate whether water conducts electricity

You will need:

a circuit with two 1.5 V cells in a cell holder, a piece of plastic-coated wire,
distilled water, a beaker, two teaspoons of salt, aluminium foil

Your teacher will show you this investigation.

• Connect the circuit with the cells,
the lamp in the lamp holder and
one length of wire.
• Test the circuit by holding the crocodile clips
together. Does the lamp light up?
• Fold two pieces of aluminium foil and put them
into the crocodile clips at the end of each wire.
This gives a larger surface in contact with
the water.
• Pour 250 ml of distilled water into the beaker.
Dip the aluminium foil ends into the water.
• Predict whether the lamp will light up.
• Observe whether the lamp lights up.
• Remove the aluminium foil ends from the water.
• Add two teaspoons of salt to the water and stir it.
Now dip the aluminium foil ends into the salt Aluminium foil
connected to a
water. Predict whether the lamp will light up. crocodile clip
• Observe whether the lamp lights up.

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 6 Electricity

Continued

Questions
1 Did your results support your predictions or not?
2 Compare the results you got with pure water
and with salty water.
3 What conclusion can you make about whether
water conducts electricity?
4 Would your body be a good or a bad conductor
of electricity? Explain why.
5 Use your answer to question 4 to explain why
it is not safe to touch the bare wires when the
circuit is closed.
6 Why is it dangerous to swim in the sea when there is a thunderstorm with lightning?

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 6.2 Does water conduct electricity?

Did you enjoy the demonstration?

Did it help you to learn about conductors and insulators?
Were you surprised to learn that your body is a conductor of electricity?

Look what I can do!

I can investigate if water conducts electricity.
I can make predictions and identify if results support predictions or not.
I know the risks and can carry out practical work safely.

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 6 Electricity

6.3 Using conductors and insulators

in electrical appliances
We are going to…
• classify materials used in electrical appliances as electrical
conductors or insulators
• see how to use electrical appliances safely
• predict whether appliances are being used safely or not
• present results in a dot plot.

Getting started
cable pylon
1 Identify the electrical appliances 1–4. cord volt
2 Where in your home do you use most
electric shock voltage
electrical appliances?
3 Do these appliances use the same electricity mains electricity wall socket
as the circuit we made in class? plug
1 3

2 4

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 6.3 Using conductors and insulators in electrical appliances

Conductors and insulators and mains electricity

In class you have made circuits with cells with
voltages of 1.5 V or 3 V. ‘V’ stands for volt. A volt
is a unit to measure the strength of electricity.
We describe the strength of a supply of electricity
as voltage. Cells with a voltage of 1.5 V or 3 V are
safe to use.
You may have seen a pylon like the one in the
photograph. Pylons carry electricity in cables
(large wires) from where the electricity is made to
where it is used in homes, factories and offices.
The voltage of electricity carried by these cables
is many thousands of volts!
Appliances like microwave ovens, electric kettles
and power drills use mains electricity. Mains
electricity has a much higher voltage than cells. In
some countries it is 110 V and in other countries it
is over 200 V.
At these high voltages, safety is very important.
The parts of an appliance that you touch must be
made from insulating material. The parts inside
the appliance are made from conducting material
so that electricity can pass through.
You know that metals, such as copper, iron and
steel, are good electrical conductors. The parts of
electrical appliances that let electricity pass
through are made of metal. For example, metal
is used for the pins in a plug. The pins allow
electricity to travel from the wall socket, through
the plug, and into an appliance such as a
kettle or television.
When we handle the plug we only touch the
cover. This is made of plastic, which is a good
insulator.
Remember to never touch a bare electric wire,
especially if your fingers are damp or sweaty.

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 6 Electricity

Activity 1

Classify materials used in electrical appliances as electrical

conductors or insulators
Look at the picture of electric wire.

Questions
1 Why is the wire covered in plastic?
2 Why is the wire made of copper?
Find three examples of appliances at home or at school.
3 Name the appliances.
4 What voltage of electricity do these appliances use?
5 Choose one of the appliances on your list. Draw a picture of it and label the
materials used. Classify the materials as conductors or insulators of electricity.
6 Look for electrical appliances at home. List them according
to the room they are in. Draw a dot plot to present your results.
You can find out how to draw a dot plot at the end of this book.

Electric shocks
If mains electricity flows through your body you will get an electric shock.
You will be badly burnt, your heart could stop beating and you could die.
Damaged electrical wiring is one of the main causes of accidents
with electricity.
Plastic insulation often wears off the copper wires –
you can get a shock if you touch the wires.
Never place an electric wire under a carpet. When people
walk on the carpet the plastic wears off the copper wires.
When bare copper wires touch each other, electricity
flows between them and this can start a fire.
Never pull a plug out like this. This damages the cord and
the wires become bare. If you handle the bare wires you
could get an electric shock. Turn off the switch before
you pull out the plug. Grip the plug, which is made of
insulating plastic, to pull the plug out of the socket.

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 6.3 Using conductors and insulators in electrical appliances

Be careful not to plug too many electrical devices into the same socket.
This can overload the socket and could give you a shock if you touch the
socket or one of the plugs. It could also cause a fire.

Activity 2

Predict safe or unsafe use of appliances

1 Predict what could happen to the person in the picture.
2 Copy and complete these sentences to explain why
this could happen.
He is pushing a ________ screwdriver into the
holes of the ________ when the power is on.
The electricity could flow from the ________
in the wall to the screwdriver in his ________ .
The wires and screwdriver are made of ________
which is a ________ of electricity.
3 Look at the picture of Mrs Mbatha at the kitchen sink.
Why should Mrs Mbatha dry her hands before
she handles the toaster?

How am I doing?
Explain the difference between a 1.5 V cell and mains electricity
to a member of your family.

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 6 Electricity

What did you learn about using electricity safely at home?

Do you think what you learnt today will be useful?

Look what I can do!

I can classify materials used to make electrical appliances as
electrical conductors or insulators.
I can understand how insulators help us to use mains electricity safely.
I can make predictions using my knowledge of conductors and insulators.
I can present my results in a dot plot.

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 6.4 Switches

6.4 Switches
We are going to…
• describe how a simple switch is used to open and close a circuit
• make a prediction and test our prediction to see if it is correct
• see that an electrical device will not work if there is a break in the circuit
• choose equipment to carry out an investigation and use it appropriately
• identify risks and carry out practical work safely.

Getting started
Look at the picture.
1 What happens when Sofia turns the switch on?
2 What happens when Sofia turns the switch off?

switch

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 6 Electricity

Putting a switch in a circuit

A switch is another component in an electrical circuit. The switch
turns the electric current on or off. It is the same idea as turning
a tap on or off.
So far you have made circuits with no switch. To break the circuit
you broke the wire. A switch lets you turn a lamp on and off
when you like, without having to break wires.

Think like a scientist 1

Make a switch

You will need:

a small block of wood, two drawing pins, a wire, a sharp knife or wire trimming
tools, a metal paper clip (not plastic coated), a plastic or wooden chopstick

drawing pin
Put together the parts as shown. paper clip
Strip the plastic off the ends of the two wood
pieces of wire.
Be careful if using the knife to strip the
plastic from the wires. Wait until your teacher
is able to help you. You could use wire trimming tools instead.
• Wind one end of each piece of wire to the drawing pins
as shown.
• Move the paper clip until it touches the other drawing pin.
You should use a wooden or plastic stick (such as a chopstick)
to do this. This completes the circuit.
• To switch off, lift the paper clip off the drawing pin.
This breaks the circuit.
Questions
1 Why do you use a metal paper clip to make the switch?
2 Why do you use metal drawing pins to make the switch?
3 Why is the base of the switch made of wood?
4 Suggest other suitable materials for making a switch.

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 6.4 Switches

Think like a scientist 2

Make a circuit with a switch

You will need:

a switch, a cell in a cell holder, a lamp in a lamp holder, 30 cm wire,
a sharp knife or wire trimming tools, scissors

• Make a circuit like the one shown.

Remember to follow the safety rules. Wait until your teacher is able to
help you if using the knife to strip the plastic from the ends of the wire.
• Predict what will happen when you close the switch.
• Close the switch. Observe the lamp. What happens?
• If the lamp does not light up, check all your
connections in the circuit. Try again.
Questions
1 Why does the lamp light up when you close the switch?
2 What must you do with the switch to break the circuit?
3 Draw the circuit you made. Label the cell, the wire, the switch and the lamp.
4 Why did you need to check your connections if the lamp did not light up?
5 Which safety rules did you follow during this investigation?

How am I doing?
• How well did your partner do in the investigation?
• Did your partner connect the components of the circuit confidently
on their own, or did they need some help or a lot of help?
• Did your partner use the switch to open or break the circuit confidently
on their own, or did they need some help or a lot of help?

Look what I can do!

I can use my knowledge of conductors and insulators to make a simple switch.
I know the risks and work safely doing practical work.
I can make a prediction and test my prediction to see if its correct.
I can see that a lamp will not light up if there is a break in the circuit.

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 6 Electricity

6.5 Changing the number of

components in a circuit
We are going to…
• investigate how changing the number or type of components in a
circuit make a lamp shine more brightly or less brightly
• identify risks and carry out practical work safely
• make predictions and identify if results support predictions or do
not support predictions
• describe simple patterns in results and make a conclusion from results.

Getting started
1 What components have you used so far to build
a circuit?
2 Where is the electricity in the circuit?
3 What pushes the electricity around the circuit? battery brightness
4 What opens and closes the circuit? brightly dimly

Cells and batteries

So far you have mostly made circuits
with one cell. Each cell stores 1.5 V of
electricity. When we have two or more
of these cells connected together we
call it a battery. The car battery in the
picture is 12 V. Your teacher used two
cells in the experiment looking at
whether water conducted electricity.
When the cell or battery is part of a
circuit, the stored energy pushes electricity
around the circuit. In the next activity you need to use a 3 V battery.

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 6.5 Changing the number of components in a circuit

Think like a scientist

What happens when we change the number of components in a circuit?

You will need:

three 1.5 V cells in cell holders, three lamps in lamp holders, a switch, wire,
a sharp knife or wire trimming tools, scissors, a stick

• Make a table to record your results like this:

Circuit Brightness of lamps

1 3 V battery, three lamps

2 3 V battery, two lamps

3 3 V battery, one lamp

4 4.5 V battery, three lamps

5 3 V battery, three lamps

• Make circuit 1 by joining two cells together

to make a 3 V battery. Make sure the positive
and negative terminals are next to each other.
• Use the scissors to cut the wire into short lengths.
Complete circuit 1 by adding three lamps in
lamp holders and a switch.
Be careful if using the knife to strip the plastic
from the wires. Wait until your teacher is able
to help you. You could use wire trimming
tools instead.
• Predict what will happen if you close the switch. Circuit 1
• Close the switch. Observe the lamps.
• Predict what will happen if you open the switch.
• Open the switch. Observe the lamps.
• Make circuit 2 by removing one lamp and a lamp holder so
that only two lamps are left in your circuit.
• Predict what will happen when you close the switch.

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 6 Electricity

Continued

Remember to follow the safety rules!

• Close the switch. Observe the lamps. Did you
notice any difference in the brightness or
amount of light from the lamps?
Record your result.
• Open the switch.
• Predict what would happen if you remove one
more lamp in a lamp holder. This means that
only one lamp remains in your circuit (circuit 3).
Test your prediction. Record your result. Circuit 2
• Now change the number of cells in your circuit.
Make circuit 4 by using three cells and three lamps in lamp holders.
• Close the switch. Observe how brightly the lamps are shining.
• Now open the switch. Decide how you can change this circuit and ask another
question about how your change to the circuit will affect the brightness of the
lamps. For example, you could remove one of the cells so that there are two
cells left (circuit 5). Predict how bright the lamps will be when you close the
switch.
• Close the switch. Test your prediction.
Questions
1 Identify two risks when doing this investigation.
2 Explain how to stay safe and avoid these risks.
3 Did the lamps shine more brightly or more dimly when you removed
one lamp from the circuit? Why do you think this happened?
4 What happened when you used only one lamp and three cells in
the circuit? Why do you think this happened?
5 Did the lamps shine more brightly or more dimly when you removed
one cell from the circuit? Why do you think this happened?
6 Identify a pattern in your results. Choose the correct alternatives
to complete these sentences:
The lamps shine less / more brightly when you add more lamps to the circuit.
The lamps shine less / more brightly when you add more cells to the circuit.

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 6.5 Changing the number of components in a circuit

Continued

7 Complete the sentence below to write a conclusion:

Changing the number of ________ or ________ in a circuit can make a lamp
________ or ________.
8 Which type of scientific enquiry did you practise in this investigation?

How am I doing?
How well did your partner do in the investigation?
Was your partner better at connecting the components of the circuit
than in the last activity?
How well did your partner add or take away components and
re-connect the circuit?
• Confidently on their own?
• Did they need some help?
• Did they need a lot of help?
How well did your partner record results?

Look what I can do!

I can change the number of lamps or cells in a circuit and observe
how this affects the brightness of the lamps.
I know the risks and work safely doing practical work.
I can make predictions and see if results support my prediction.
I can identify a pattern in results and make a conclusion.

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 6 Electricity

Project: Batteries
All the circuits you have made included a cell or a battery. These
batteries contain chemical substances that react together. This
reaction supplies energy. The energy pushes the electricity around
the circuit. How did scientists make this discovery?

The Baghdad battery

In June 1936 workers were building a new railway near the city of
Baghdad, in present-day Iraq. They found an ancient tomb (a place
where a person was buried when they died).
Archaeologists (scientists who study ancient remains) identified things
in the tomb to be 2000 years old.
One of the old objects they found in the tomb was a clay jar. The jar
had an iron rod coming out of the centre, surrounded by a tube made
of copper. Scientists made copies of the object. When they filled the
tube with an acid such as vinegar, it produced between 1.5 and 2 volts
of electricity between the iron and copper. Archaeologists think that
people who lived 2000 years ago could have used batteries like this!

Galvani’s discovery
Luigi Galvani was an Italian doctor. In about 1780
he discovered current electricity. He hung a frog's
leg on copper hooks over an iron railing. He
observed that the frog’s leg muscles twitched
(moved). Galvani was correct when he said that
the twitching was caused by an electrical current.
But he thought that the current came from the
frog’s legs and called it ‘animal electricity’.

The voltaic pile

Alessandro Volta was an Italian university
professor. He repeated Galvani's experiments
many times with different materials. From these
experiments he came to the conclusion that it
was the two different metals, not the frog’s leg,
that produced the electricity. The frog’s leg
showed the presence of the electricity.

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 Project: Batteries

Continued
In 1800, after many experiments, he developed his own battery and
named it after himself – the ‘voltaic pile’.

Continue the story…

Find out more about Alessandro Volta’s battery called the voltaic pile.
You can use reference books or the internet.
• Describe Volta’s battery and
how it worked.
• Put your information onto a
sheet of paper. Illustrate it
with diagrams or pictures.

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 6 Electricity

Check your progress

1 Write one word or two words to describe each of the following:

a A device for closing or opening a circuit.
b A device in a circuit for holding a lamp in place.
c Something that pushes electricity around a circuit.
2 Which of the following materials are insulators of electricity?
gold cork plastic aluminium
3 In the circuit alongside:
a What does the component A do?
b What must you do to this circuit to turn the
lamp off? A
c If you added a second lamp to the circuit,
would the lamps glow more brightly or
more dimly?
d If you added another 1.5 V cell to the
circuit, would the lamps glow more brightly or more dimly?
4 Arun’s mother asked him to fix the iron because it was not working.
Arun got an electric shock!
What had Arun forgotten to do?

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 Check your progress

Continued

5 Here are four steps, A to D, that you should take to replace

a light lamp safely with a new one.
The steps are in the wrong order. Re-arrange the steps so that
they are in the correct order.
A Unscrew the old light lamp.
B Wait for the lamp to cool down.
C Switch the electricity off.
D Screw in the new light lamp.

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