Science
NEW SOUTH WALES
D E PA R T M E N T
OF EDUCATION
AND TRAINING
Stage 4
Introduction to
electricity
Set 1: Finding out about electricity
1
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Number: 31718
Title: Introduction to electricity
This publication is copyright New South Wales Department of Education and Training (DET), however it may contain
material from other sources which is not owned by DET. We would like to acknowledge the following people and
organisations whose material has been used:
Extract from Science Syllabus Years 7-10 © Board of Studies, NSW 2003
Introduction
pp vi-viii
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CLI Project Team acknowledgement:
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Editors:
Illustrator:
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Dick Alliband and Rhonda Caddy
Barbara Gurney
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Published by
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Copyright of this material is reserved to the Crown in the right of the State of New South Wales. Reproduction or
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© State of New South Wales, Department of Education and Training 2005.
i
Introduction to electricity
The hand points to the names of the lessons in this set.
☞
Set 1
Finding out about electricity
Lesson 1
What is electricity?
Lessons 2 and 3
Investigating static electricity
Lesson 4
Energy transformations
Lesson 5
Getting ready for Set 2
Set 2
Making an electrical circuit
Lessons 6 to 8
Making a tester
Lesson 9
Resistor coding and decoding
Lesson 10
What is an electrical circuit?
Set 3
Investigating electrical circuits
Lessons 11 and 12
Energy for a circuit
Lesson 13
Diagrams for circuits
Lesson 14
Predicting
Lesson 15
Investigating
Introduction to electricity
Set 1
ii
Set 1: Finding out about electricity
Contents
What will you learn in Set 1?............................................................... iii
What do you need for Set 1?................................................................. i v
Lesson 1
What is electricity? .............................................. 1
Lessons 2 and 3
Investigating static electricity ............................ 9
Lesson 4
Energy transformations.................................... 19
Lesson 5
Getting ready for Set 2....................................... 23
Suggested answers................................................................................... 27
Send-in pages............................................................................................ 31
Introduction to electricity
Set 1
iii
What will you learn in Set 1?
In Set 1, you will have opportunities to achieve and demonstrate
the following statements.
•
draw a concept map about electricity
•
define static electricity
•
define dynamic electricity
•
electrostatically charge objects by rubbing them
•
electrostatically charge objects by touching them with
a charged object
•
explain why objects become electrostatically charged
•
match diagrams and headings with text about electrostatics
•
demonstrate that electrostatically charged objects attract
uncharged objects
•
demonstrate that like charges repel
•
recall that opposite charges attract
•
write simple equations for transformations of energy
Introduction to electricity
Set 1
iv
What do you need for Set 1?
Here is a reminder of the items you need for Set 1. To save time, it
might be a good idea to get all these things ready before you start.
Lesson 1
•
a plastic comb or a plastic ruler
•
woollen material or a woollen jumper
•
some scrap paper, torn into pieces that are smaller than 1 cm
in any direction.
Lessons 2 and 3
•
a balloon
•
some woollen fabric (or a woollen jumper)
•
2 stick-shaped objects made from the same kind of plastic;
for example, two plastic combs, plastic rulers or plastic
teaspoons
•
running water from a tap
•
a tiny piece of torn paper, smaller than 1 cm in any direction
•
a clock glass or a flattened plastic bottle such as a shampoo
bottle.
Lesson 5
Electronic kit, e.g. from Dick Smith or Jaycar stores, containing:
•
•
•
•
•
•
•
•
•
•
battery
board
bag of springs and clips (or screws and washers)
silver-coloured wire
two plastic-coated wires with alligator clips
screwdriver (if you have screws and washers)
battery clip
one LED (light emitting diode)
one protection diode
one 390 ohm resistor (orange white brown gold bands).
Introduction to electricity
Set 1
1
Lesson 1
What is electricity?
What do you think electricity is?
In the space below, make a concept map by writing as many words
as you can think of that are related to electricity. Then draw lines
to link the ideas to electricity or each other, if you can.
Label each line with the reason that you think the words are
linked.
electricity
Introduction to electricity
Set 1
2
Everyone knows something about electricity so I’m sure that you
came up with some good ideas about what electricity is.
But do you think your ideas about electricity are very scientific?
You’ll be able to judge by the end of this lesson.
Here is an example of electricity that you may not have thought about.
For this activity, you will need:
•
a plastic comb or a plastic ruler
•
woollen material or a woollen jumper
•
some scrap paper, torn into pieces that are smaller than 1 cm
in any direction.
What to do:
1.
Spread the pieces of torn paper apart on the desk in front of
you.
2.
Rub the comb (or ruler) firmly with the woollen material
for about 10 seconds.
3.
Immediately hold the comb just above the pieces of paper,
without touching them. What happens?
There is a sample answer in the answer pages on page 27.
The effect you have just observed is called a phenomenon
(say FEN-OH-men-on). It is something that happens in the world
around you that you can observe. When you think about more
than one phenomenon, they are called phenomena.
Here is another phenomenon that you may have noticed.
Try it tonight, if you can.
Do you have some clothes made from synthetic material that
sometimes stick to your skin when you wear them or crackle
when you take them off? Try putting the clothes on and rubbing
them with your hands and arms. Then take them off in a dark
room and shake them sharply. You will notice tiny sparks flicking
and jumping all over your clothes!
Introduction to electricity
Set 1
3
Have you slid down a plastic slippery dip or walked across new
carpet, then got a little electric shock when you touched something
made from metal?
These are all examples of phenomena that scientists call static electricity.
Think about these examples. How are they all similar?
How are the examples alike in the way that static electricity is caused?
How are the examples alike in the observations that are made?
Did you notice that each phenomenon is caused when something is
rubbed? You rubbed the comb with woollen material, clothes rubbed
your body, you rubbed against a slippery dip and your feet rubbed over
carpet.
Did you notice that, in each situation, things moved or were stuck
together, or tiny sparks jumped?
These are common features of static electricity.
Static electricity involves objects becoming electrostatically charged.
The charge stays on the object, without moving. That is why this
kind of electricity is called static electricity; static means not moving
or changing.
Write a definition for static electricity.
There is a sample answer in the answer pages.
Static electricity isn’t always static; it can move. The sparks you
observed are electrical energy jumping from one place to another.
Lightning is a really big example of electrical energy jumping through
air.
Introduction to electricity
Set 1
4
What is electrical charge?
Objects can gain an electrostatic charge when they are rubbed. Why?
The easiest way to explain is to look at the parts of an atom.
You probably remember that an atom is the smallest particle of
matter that can exist on its own. Everything is made from atoms.
Atoms are very, very small. About 250 000 million atoms would cover
the full stop at the end of this sentence. Atoms are usually pictured as
very small balls. But inside each atom, there are even smaller particles.
These particles that make up an atom can be represented in a diagram.
Here is a diagram of an atom of an element called boron.
electron
neutron
proton
nucleus of atom
(It is different from the
nucleus of a living cell.)
The boron atom is composed of electrons, neutrons and protons.
1.
Which of these do you think has:
(a) a positive electrostatic charge? ______________________
(b) a negative electrostatic charge? ______________________
(c) no electrostatic charge? ____________________________
Check your answers now.
Did you notice that there are five protons and five electrons in this
atom? This is important. The pluses and minuses can cancel each
other out.
So when there is an equal number of protons and electrons, the atom
has no overall electrical charge. It is neutral, or uncharged.
But what can happen if the atom is rubbed?
Electrons from the outside of the atom can be rubbed off.
Protons are not rubbed off. They stay in the nucleus of the atom.
Introduction to electricity
Set 1
5
Here is a diagram of an atom of boron that has lost some electrons.
electron
neutron
proton
2.
This atom has an overall electrical charge.
Would it be a positive charge or a negative charge? Why?
3.
The electrons that were rubbed off this atom became stuck to
another atom. Do you think that that other atom would now
be positively charged or negatively charged? Why?
Please check your answers.
You have seen that there are two kinds of electrical charge –
positive charge and negative charge. Objects become charged
when negative charges called electrons move from one object to
another. And electrons can be moved when objects rub together.
4.
Complete the sentences below to make a summary about
electrical charges and static electricity.
Static electricity describes
when objects have extra electrical
This electrical charge may be
Objects become charged when electrons are
or off atoms in the objects.
Check your answers now.
Introduction to electricity
Set 1
that occur
.
or
.
onto
6
Another example
Static electricity, also called electrostatics, was studied a lot in the 1800s.
Scientists discovered a material (rubber mixed with molten sulfur)
called ebonite that easily becomes electrostatically charged. Ebonite
looks like the black keys on an old piano. Scientists make it into sticks
about 30 cm long and 1 cm in diameter, which are called ebonite rods.
When ebonite is rubbed with woollen material (often called
flannel), ebonite becomes negatively charged.
1.
Label the ebonite rod and flannel in the diagram below.
2.
Put some minus signs (–) on the ebonite rod to show
that it is negatively charged.
3.
What have been rubbed onto the
ebonite rod to give it a negative charge?
____________________________________
4.
Where did these electrons come from?
5.
Since atoms in the flannel have lost electrons,
what is the electrical charge on the flannel? _______________________________
6.
Put some plus signs (+) on the flannel to show
that it is positively charged.
(How many plus signs should you use?
The same number as the number of minus signs
that you drew onto the ebonite rod.)
_____________________________________
If you’d like to check your diagram, turn to the answer pages.
Introduction to electricity
Set 1
7
plate
A device called an electroscope, that
detects electrostatically charged objects,
was developed in the late 1700s.
The vane in the electroscope moves
when a charged object touches or
comes near its plate.
vane
What happens when an ebonite rod touches or comes near the
plate of an electroscope?
negatively charged ebonite rod
–
–
–
–
7. Write a sentence about what you
observe from this diagram.
electroscope
Compare your sentence with the one in the answer pages.
Scientists also found that the electroscope vane moved when a
wire was used to join the charged rod and plate.
–
–
–
–
wire
8.
Suggest an explanation for what is happening.
Introduction to electricity
Set 1
8
Did you think that electrons must be travelling through the wire
from the ebonite rod to the electroscope? Well done if you did,
because that is what scientists thought too.
So electrical charges can be made to travel through a wire.
And when they do, scientists say that an electric current is flowing.
Scientists used the term dynamic electricity to describe
phenomena that involved these moving electrical charges.
People still talk about static electricity. For most people, it is more
of a nuisance than a help. But dynamic electricity, what we
commonly think of as electricity, has become vital in our modern
world. Almost everything you do and have has involved
electricity in some way.
9.
Complete the sentences below to make a summary about
electric current and dynamic electricity.
Dynamic electricity describes
that occur
when electrical charges move through a
.
The electrical charges are
.
An electric
is produced when electrons
travel through a wire.
Check your answers now.
Have you noticed that the adjectives (describing words) electric, electrical
and electrostatic have been used to describe objects and charges in this
lesson? You'll see these words often in this unit about electricity!
In most situations, you can use the words electric and electrical to
replace each other. Electrostatic can also be used to mean electric
or electrical when you are talking or writing about static electricity.
Electrostatic is seldom used when you consider moving, or
dynamic, electricity.
Exercise 1
How scientific do you think your ideas about electricity were
at the beginning of the lesson? Have any of your ideas about
electricity changed?
In send-in Exercise 1, you will make another concept map
about electricity. Please complete this exercise now.
Introduction to electricity
Set 1
9
Lessons 2 and 3
Investigating static electricity
In these lessons, you will investigate some more examples of
phenomena caused by static electricity. Remember, these are caused
by a build-up, or accumulation, of electrical charge on an object. This
electrical charge can be either positive or negative.
Some party tricks
Static electricity is fun to use in tricks. As you perform the tricks described,
think about what they tell you about electrostatically charged objects.
A charged object near an uncharged object
What happens when an electrostatically charged object is placed near an
uncharged object? You have already begun to investigate this question,
when you put a charged comb near some neutral, or uncharged, pieces
of paper. Here are some more activities to do and consider.
For these activities, you will need:
•
a balloon
•
some woollen fabric (or a woollen jumper)
•
a plastic ruler or a plastic teaspoon
•
running water from a tap.
What to do:
1.
Inflate (blow up) the balloon to normal size and knot
it. Stretch out your arm and put the balloon under it.
What happens?
I hope that wasn’t a surprise!
You would expect the balloon to fall to the floor, right?
Introduction to electricity
Set 1
?
10
2.
Rub the balloon vigorously all over with the woollen material.
(It is often easiest to put on a woollen jumper then rub the
balloon against you.)
Do you think the balloon has become electrically charged? Why?
The balloon may have become electrically charged because rubbing
can cause charge to accumulate (build up) on an object.
3.
Try the test again. What happens?
?
4.
Now put the charged balloon near your hair.
What happens?
If it is a dry day, you can make the charged balloon attract many
light objects and stick in lots of places. (The day needs to be dry
because water in the air can ‘steal’ electrical charge from the balloon.)
5.
Now take one of your plastic objects; I will call it a ruler.
Go to a tap and start the water running very gently
so that it makes a thin stream.
6.
Charge the ruler by rubbing it with your woollen material
for about 10 seconds.
Then put it beside (not in)
the stream of water.
Draw what happens to the water.
kitchen tap
hold charged object here
charged object
thin stream of water
Look in the answer pages.
Introduction to electricity
Set 1
11
Here again is the question that you have been investigating.
What can happen when an electrostatically charged object is
placed near an uncharged object?
Write a general answer for this question.
There is a sample answer in the answer pages.
A charged object near another object with the same charge
What happens when an electrostatically charged object is placed
near another object that has the same electrical charge?
Here are some activities to do and consider.
For these activities, you will need:
•
some woollen fabric (or a woollen jumper)
•
2 stick-shaped objects made from the same kind of plastic;
for example, two plastic combs, plastic rulers or plastic
teaspoons
•
a tiny piece of torn paper, smaller than 1 cm in any direction
•
a clock glass or a flattened plastic bottle such as a shampoo bottle.
What to do:
1.
Balance one ruler (or spoon) across a clock glass (or plastic
bottle) so that the ruler can spin easily.
Here are two ways you could make it balance.
2.
What do you predict would happen if you brought a charged
object near the end of the ruler across the clock glass?
Introduction to electricity
Set 1
12
3.
Charge the other ruler and
test your prediction.
What happens?
charged
ruler
uncharged
ruler
clock
glass
You know that an electrically charged
object can attract a neutral, or
uncharged, object so you should have
observed that the uncharged ruler
moved towards the charged one.
4.
Repeat the activity but this time make both rulers charged.
(Rub one ruler and balance it on the clock glass. Then rub the
other ruler and put it beside the rubbed end of the balanced
ruler.)
What happens?
If you did not observe that the charged objects move apart, try Step
4 again.
5.
Now I’d like you to look more closely at the first activity you
did in this unit.
Rub your plastic object to make it charged.
Pick up the scrap of paper by attracting it with the charged
object. Watch the piece of paper until something happens.
What happens?
Attract the piece of paper again and see if the same thing
happens. You can do it over and over.
How can you explain this phenomenon?
Introduction to electricity
Set 1
13
6.
Here is an explanation but the sentences in it have been jumbled.
Number them from 1 to 7 to make the correct order.
❒
❒
❒
❒
❒
❒
❒
The charged comb attracts the neutral paper.
The comb and the paper share the electrical charge.
The comb becomes electrostatically charged when it is
rubbed.
The paper drops off the comb onto the table.
The paper now has the same electrical charge as the comb.
The paper moves towards the comb and sticks to it.
The paper moves away from the comb because they both
have the same electrical charge.
Turn to the answer pages to check your answer.
Two charged objects move apart if they both have the same electrical
charge. Scientists say that they repel each other.
Two negatively charged objects will push each other apart.
So will two positively charged objects. Like charges repel.
But what happens if the objects have different charges?
A positively charged object near a negatively charged object
Positive and negative are called opposites of each other.
So if one object is positively charged and the other is negatively
charged, you can say that the objects have opposite charges.
When two opposite charges are near each other, they move
towards each other. They are pulled together, or attracted.
Opposite charges attract.
It is hard for you to do an activity at home to test opposite charges
because most things in your home become positively charged
when you rub them. If you attend a minischool, you may be able
to perform some investigations using the scientific equipment
described on the next page.
If you are particularly interested, contact your teacher. You teacher
may help you to plan a student research project about static electricity.
Introduction to electricity
Set 1
14
A summary using scientific equipment
On page 17, there are diagrams about the following situations.
Cut out the diagrams and match them with the descriptions.
When an ebonite rod is rubbed
with flannel, the ebonite rod
becomes negatively charged (and the
flannel becomes positively charged).
When a plastic rod called a
perspex rod is rubbed with fabric
called silk, the perspex rod becomes
positively charged (and the silk
becomes negatively charged).
When a charged rod touches an
uncharged, or neutral, electroscope,
charge is shared between the rod
and the electroscope.
The electroscope becomes charged
too.
Introduction to electricity
Set 1
15
When two rods with opposite
electrostatic charge are brought
close together, they attract each
other and move together.
When two rods with the same
electrostatic charge are brought
close together, they repel each other
and move apart.
Introduction to electricity
Set 1
16
A charged rod will attract
a neutral, or uncharged, object.
Look again at the two descriptions and diagrams on page 14.
They present information about one main idea in electrostatics.
(Electrostatics is the study of static electricity.)
Find the box on page 17 that contains a heading about this main idea.
Cut out the box and put it into the space above the descriptions
and diagrams on page 14.
Then find the heading for the two descriptions and diagrams on page
15.
The remaining heading should match the description and diagram
on this page.
Finally, look at all the diagrams again and decide which rods will
move.
Draw an arrow to show the direction that each rod moves.
Would you like to check your answers?
Look in the answer pages.
Use sticky tape or glue to secure the headings and diagrams
into their correct places.
Exercises 2.1 and 2.2
You will need to use information and ways of writing about
electrostatically charged objects to complete these send-in exercises.
Introduction to electricity
Set 1
17
–
clock
glass
charged
perspex rod
Use the diagrams and headings below to complete pages 14 to 16.
charged
perspex rod
electroscope
clock
glass
charged
perspex rod
charged
perspex rod
clock
glass
perspex rod
charged
ebonite rod
silk
electroscope
+
charged
ebonite rod
ebonite rod
Ways to make an object electrostatically charged
How objects with electrostatic charge affect each other
How electrostatically charged objects affect neutral objects
Introduction to electricity
Set 1
charged vane
neutral
ebonite rod
flannel
18
Introduction to electricity
Set 1
19
Lesson 4
Energy transformations
Have you ever played with a transformer toy? What does it do?
When scientists talk about energy transformations, they mean that
energy changes from one form of energy into another. Just as all the
parts of the transformer toy are still there after it has changed from
one toy into another, all the energy still exists after it changes form.
What energy transformations have you seen so far in this unit?
Giving an object an electrostatic charge
When you rubbed the object to make it charged, what form of
energy were you using? Underline the best answer.
electrical
heat
sound
kinetic
light
potential
nuclear
Rubbing is movement, so I think kinetic is the best answer. Did
you?
What form of energy did your kinetic energy become?
Underline the best answer.
electrical
heat
sound
kinetic
light
potential
nuclear
If you connected the electrostatic charge on the object with
electrical energy, you are right!
Energy transformations using dynamic electricity
In Lesson 1, you learned about how electrical charges can move
through wire. And when they do, an electric current is produced.
This is an example of dynamic, or moving, electricity.
Many of the energy transformations that we use in everyday life
involve dynamic electricity. Let’s consider some examples.
Introduction to electricity
Set 1
20
A simple circuit
You’ll learn about what a circuit is in Set 2. For the moment,
concentrate on using information you already understand
to solve some problems about energy transformations.
Here is a diagram of a simple circuit.
Electric current can travel through the wires in the circuit.
globes giving out light energy
and some heat energy
battery
with
chemical
energy
wire
In the battery, chemical energy is transformed into electrical energy.
The electric current through the wire carries electrical energy from
the battery to the other parts of the circuit.
The current isn’t used up in the circuit or changed into anything
else. It is the electrical energy that is changed into other forms of
energy. In the light globes in this circuit, electrical energy is
changed into heat energy then light energy. When the metal
filament is hot enough light energy is given out.
You can show the energy transformations in a simple equation.
chemical
energy
Æ
electrical
energy
Æ
light
energy
Æ
heat
energy
This equation means that chemical energy is changed, or transformed,
into electrical energy. Then electrical energy is changed into heat and
light. It’s easier to read as an equation, isn’t it!
Now it’s your turn to look at some energy transformations that
occur in appliances in your home.
Introduction to electricity
Set 1
21
Examples of energy transformations in electrical appliances
When you plug in and switch on an appliance, an electric current
flows through the appliance. This current carries electrical energy
to the appliance. In the appliance, electrical energy is changed into
other forms of energy.
You are going to look at some common appliances and deduce the
energy transformations that happen in each appliance.
First think about a television.
What energy transformations happen here?
Did you say that electrical energy is changed into light energy and
sound energy?
Write these transformations as a simple equation.
The answer is at the bottom of the page.
Because they are all forms of energy, you can leave the word
energy out of the equation. So your equation becomes:
electrical Æ light + sound
Consider another appliance – an electric fan.
Write an equation for the energy transformations that occur in it.
If you’d like to check your answer, turn to the answer pages.
Here is the equation for the transformations of energy in a television.
light
sound
electrical
Æ
+
energy
energy
energy
Introduction to electricity
Set 1
22
The table below lists some appliances that you may have in your
home. Fill in the table by adding an equation for the energy
transformations that occur in each device. (You have already done
the first two answers on page 21 so I have filled them in for you.)
Appliance
Energy transformations
television
electrical Æ light + sound
electric fan
electrical Æ kinetic
radio
electric stove element
electric jug
CD player
computer
Check your answers in the answer pages. If you do not get the same
answers, discuss the transformations with a friend or family
member. Talking about the change usually helps you to see the
problem more clearly. If you still cannot understand the answers
in the answer pages, contact your teacher.
In this lesson, you thought about situations and devices that
involve electrical energy. You recalled that electrical energy is
very useful when it can be changed, or transformed, into other
forms of energy. You have summarised energy transformations
in common situations by writing simple equations.
Exercise 4
In send-in Exercise 4, you will identify some common objects
that use electrical energy and write simple equations for
the energy transformations that occur in these appliances.
Please complete this exercise now.
Introduction to electricity
Set 1
23
Lesson 5
Getting ready for Set 2
Now that you have a better understanding of what electricity is, you are
ready to build a ‘tester’ that can show when an electric current is
flowing.
You will need parts from a simple electronics kit such as those supplied
by Dick Smith or Jaycar stores. Don't panic! You don't need to be an
expert in electronics. (Electronics is the technology and science of using
electric currents for making, sending, receiving and storing information.)
You are going to learn all you need as you progress through the unit.
Sorting out your electronics equipment
Before you do anything, you should know that one of the
assessment items for this unit involves returning your equipment
after you have used it. You will need to be organised in how you
unpack the kit if you are to pack up well.
On the next page is the heading ‘Checklist’.
The first five items, or components, on the checklist are:
• battery
• board
• bag of springs and clips (or screws and washers)
• silver-coloured wire
• two plastic-coated wires with alligator clips.
Alligator clips have teeth like alligators or crocodiles. Most of
the alligator clips are hidden by a plastic cover. All that you can
see of them is some silver teeth sticking out of the end of the
plastic.
Find these five items. As you identify each item, put a tick in the
box next to its name in the checklist on the next page.
Introduction to electricity
Set 1
24
Checklist
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
battery
board
bag of springs and clips (or screws and washers)
silver-coloured wire
two plastic-coated wires with alligator clips
screwdriver
battery clip
LED (light emitting diode)
protection diode
390 ohm resistor
You should have five or six items left on the checklist to identify.
What to do next
Do you need a screwdriver? You need one if you have screws and
washers. Tick this item in the checklist if you have one.
Now find the battery clip. It has two plastic coated wires joined to
it,
one red and one black.
The battery clip looks like this.
When you identify the battery clip, put a tick in the box next to its
name in the checklist.
Introduction to electricity
Set 1
25
Find the LED (say L-E-D). The LED looks like a little plastic light
globe with two wire legs. LEDs are usually red but can be other
colours such as yellow or green. When you have found the LED,
put a tick in the box next to their name in the checklist.
A protection diode looks like a black plastic cylinder with a wire
sticking out each end. There should be a silver-coloured band
near one end of the cylinder.
A protection diode looks like this.
When you have identified the protection diode,
put a tick in the box next to its name in the checklist.
Resistors are small parts that resist the flow of electricity.
Coloured bands on a resistor use a code to show the size of its
electrical resistance.
The colours of the bands on 390 ohm resistors are usually, in order,
orange, white, brown and gold.
When you have identified the resistor, put a tick in the box next to
its name in the checklist.
If you think that you can look at each item of equipment and
remember its name, go on to the next section on the next page.
If you don't think you are ready to do a test, go over this section
again, then do the test.
Introduction to electricity
Set 1
26
Test yourself
This test has been put in to help you. Don't be tempted to leave it
out.
Without looking at the first part of this lesson, pick up any item
and tick in the box to show than you can identify the item. Keep
going until you have identified all the items in the kit.
If you discover that you can't identify all the items, go through
this lesson again then test yourself.
When you have mastered this knowledge, you are ready to start
making your tester. You can say that you have mastered this
knowledge when you get 100% on the mastery test.
Mastery test checklist
❏
❏
❏
❏
❏
❏
❏
❏
❏
❏
battery
board
bag of springs and clips (or screws and washers)
silver-coloured wire
two plastic-coated wires with alligator clips
screwdriver (if you have screws and washers)
battery clip
LED
protection diode
390 ohm resistor (orange white brown gold bands)
Introduction to electricity
Set 1
27
Suggested answers
Lesson 1
What is electricity?
The pieces of paper jumped up and stuck to the comb.
You may even have seen some pieces of paper hanging from
other pieces that were clinging to the charged plastic.
Page 2
3.
Page 3
Static electricity refers to phenomena that occur when objects
become electrostatically charged.
What is electrical charge?
Page 4
1.
(a) proton (because it has a plus sign on it)
(b) electron (because it has a minus sign on it)
(c) neutron (because it has no sign on it; it is the only one left)
Page 5
2.
The boron atom would have a positive charge because it has lost
two electrons. (It has more protons [positives] than electrons
[negatives].)
3.
The other atom would be negatively charged because it has
gained two extra electrons. (It will have more electrons
[negatives] than protons [positives].)
4.
Static electricity describes phenomena that occur when objects
have extra electrical charge. This electrical charge may be positive
or negative. Objects become charged when electrons are
rubbed onto or off atoms in the objects.
Another example
Page 6
–
–
–
–
+
ebonite rod
+
+
+
flannel
Introduction to electricity
Set 1
28
Lesson 1 continued
Page 7
7.
The vane in the electroscope moved when the plate of the
electroscope was touched with the ebonite rod.
Page 8
9.
Dynamic electricity describes phenomena that occur when
electrical charges move through a wire. The electrical charges
are electrons. An electric current is produced when electrons
travel through a wire.
Lessons
2 and 3
Investigating static electricity
A charged object near an uncharged object
Page 10
charged object
The stream of water bends
towards the charged object.
Page 11
An uncharged object can move towards a nearby electrostatically
charged object.
A charged object near another object with the same charge
Page 13
6.
Here is the best order for the explanation.
2
❒
4
❒
1
❒
7
❒
5
❒
3
❒
6
❒
The charged comb attracts the neutral paper.
The comb and the paper share the electrical charge.
The comb becomes electrostatically charged when it is
rubbed.
The paper drops off the comb onto the table.
The paper now has the same electrical charge as the comb.
The paper moves towards the comb and sticks to it.
The paper moves away from the comb because they both
have the same electrical charge.
Introduction to electricity
Set 1
29
Lessons 2 and 3 continued
A summary using scientific equipment
Page 14
Ways to make an object electrostatically charged
Top diagram
–
+
Bottom diagram
charged
ebonite rod
flannel
ebonite rod
electroscope
perspex rod
electroscope
silk
charged vane
Page 15
How objects with electrostatic charge affect each other
Top diagram
Bottom diagram
charged
perspex rod
charged
ebonite rod
charged
perspex rod
clock
glass
charged
perspex rod
Introduction to electricity
Set 1
clock
glass
30
Lessons 2 and 3 continued
Page 16
How electrostatically charged objects affect neutral objects
charged
perspex rod
neutral
ebonite rod
Lesson 4
clock
glass
Energy transformations
Examples of energy transformations in electrical appliances
Page 21
electrical Æ kinetic + sound
or
electrical Æ kinetic
How did I get this answer? Parts of the fan move when the fan is
switched on. Moving energy is called kinetic energy. You might
have heard a noise, or sound energy, when the fan is switched on.
Most electrical fans make noise (sound energy) but it is often left
out of an equation summarising the energy transformations
because it isn’t a useful form of energy when it comes from a fan.
It is more of a nuisance.
Page 22
Here is the completed table.
Appliance
Energy transformations
radio
electrical Æ sound
electric stove element
electrical Æ heat + light
electric jug
electrical Æ heat + sound
CD player
electrical Æ sound
computer
electrical Æ light + sound
Introduction to electricity
Set 1
31
Send-in page
Lesson 1:
Name
______________________________
What is electricity?
Exercise 1
In the space below, draw a concept map about electricity.
It does not need to be very complicated but it must include these
terms.
dynamic
electrons
electric current
electrical charge
negative
positive
spark
static
You can add other words if you like.
Then draw lines to link the terms to the word electricity or to
each other, if you can. Label each line with the reason that you
think the terms are linked.
electricity
Introduction to electricity
Set 1
32
Introduction to electricity
Set 1
33
Send-in page
Name
Lessons 2 & 3:
______________________________
Investigating static electricity
Exercise 2.1
Here is a description of an activity that you have done.
A comb was rubbed firmly with flannel. Then the comb was
held near a small scrap of paper. The paper jumped up and
stuck onto the comb.
After a short while,
the paper dropped off the comb onto the table.
1.
There are two places in this description where objects become
electrostatically charged. Underline them.
(Do not underline everything! Underline as few words as
possible.)
2.
(a) Label your first underlining, A.
Describe how the object has gained its electrostatic charge.
(b) Label your second underlining, B.
Describe how this object has gained its electrostatic charge.
3.
Rewrite the last two sentences of the description in your own
words. Use the words repelled and attracted in your sentences.
Introduction to electricity
Set 1
34
Exercise 2.2
Complete the sentences below to describe how the electrostatically
charged objects in the diagrams are affecting each other.
charged
ebonite rod
charged
ebonite rod
clock
glass
These charged rods move
______________________
each other because they have
_________
electrostatic charge.
charged
perspex rod
charged
ebonite rod
clock
glass
These charged rods move
Introduction to electricity
Set 1
______________________
35
Send-in page
Lesson 4:
Name
______________________________
Energy transformations
Exercise 4
Here is a photograph of a corner of a family's living room.
Which things in this photograph need electrical energy to operate?
Choose two of them and write an equation for the energy
transformations that occur in each appliance.
Name of appliance
Equation for energy transformations
1.
2.
Introduction to electricity
Set 1
36
Introduction to electricity
Set 1