Course: Science and Elementary Technology, Topic: Unit 15 Magnetism

General

Unit 15 Magnetism
1. Study the pictures below

2. What is going on in the pictures?
3. What can you advise the mother of the child to do to help her
separate the iron fillings with ease? Why is this possible?
15.1 Types of Magnets
Find out
1. The definition of a magnet.
2. The various types of magnet.
Activity 15.1 Investigating the meaning of the term
“ Magnet”
1. Research from library books or search engine on meaning of
the term “ magnet”.
2. Discuss on different types of magnet
3. Write down a short note and do a presentation to other class
members.
• A magnet is an object that attracts materials usually made of iron
or steel.
There are two main type of magnets:
• Natural magnets
• Artificial magnets

a) Natural magnets
These are magnets that are found naturally in the earth’s crust. Example
magnetite/Lodestone.
b) Artificial magnets
These are magnets made by human beings from magnetic materials.
Remember!
Magnets are used in various electrical appliances e.g Radio, Television
freezer e.t.c
15.2 Composition of magnets
Activity 15.2 Making a temporary magnet
What you need
• Nail, piece of copper wire, a dry cell, pins or paper clips, masking
tape and switch.
What to do
1. Wrap the copper wire to the nail several times as shown below.
2. Connect the wire ends to the two terminals of the dry cell using
masking tape.
3. Bring the paper clips or pins close to the nail. What happens?
4. Now, remove the wire ends from the dry cell terminals and
connect through the switch. Connect to the dry cell as explained
in procedure 2 above.
5. Switch on the switch and bring the pins close to set up. What
happens?
6. Now, switch off the switch and bring the set up close to the pins
or paper clip close to the set up again. What happens?
7. What does the findings in this experiment tell you about the
nature of the magnet that you have just made? How is it different
from the normal bar or horse-shoe magnet?
Activity 15.3 Making a temporary magnet
What you need
• Permanent magnet, nail or paper clip, needle or pin.
What to do
1. Rub a paper clip or a nail along the length of a permanent magnet
as shown below.
Note: Move the paper clip or nail in only one direction. Do not rub back
and forth!
2. Continue rubbing the paper clip and the magnet about 50 times or
more.
3. Use the nail or paper clip to touch the needle or pins. What do you
observe? What do you think happened? The nail on paper clip picks
up the needle or pins. This is because it became magnetized.
Rubbing a magnet a few times over an unmagnetized piece such as an iron
nail as in the activity above, you can convert the nail into a temporary
magnet. This is because the nail becomes magnetized.
The magnet made in Activity 15.3 above is temporary magnet called an
electromagnet.
• Temporary magnets loose their magnetic properties after
sometime. Iron which is magnetically soft is used to make temporary
magnet.
• A permanent magnet on the other hand retain their magnetism
over a long period of time. Steel/ferromagnetic material is used to
make permanent magnet. Example: Horse-shoe magnet.
Natural magnet is composed of substances created by nature, which
have the property of attraction.They have properties of iron fillings e.g
iron ore, magnetite e.t.c
15.3 Characteristic of magnets
Activity 15.4 Investigating the characteristics of
magnets
What you will need
• Two bar magnets
• Items such as pins, paper clips, nails, rubber, pencil, pieces of wood,
coin.
• String
What to do
1. Put the items above on a table.Move a magnet over them as
shown below. What happens?
2. Suspend one bar magnet using a string as shown below
3. Bring the north pole of the second magnet near the south pole
of the suspended magnet. What happens?
4. Bring the north pole of the second magnet close to the north
pole of the first magnet. What happens?
Give reasons for your observations in this activity.
5. Write short notes about what you think magnets are, what they
are made of and their characteristics.

Magnets have the following characteristics:
1. They have two poles - North pole and South pole.
2. Unlike poles of magnet attract while like poles repel.
3. When a bar magnet is suspended, it rests with its South pole pointing
North of the earth’s magnetic pole.
4. Magnets attract magnetic materials but do not attract nonmagnetic
materials.
5. Magnetic force can pass through non-magnetic materials.
Magnetic forces and magnetic materials
Find out
The difference between magnetic and non-magnetic materials.
Activity 15.5 Investigating magnetic force
What you need
• Magnets of various sizes,
• White sheet of paper,
• Sewing needle or safety pins,
• Pieces of glass, a coin-sized cross section of cork,
• Iron fillings,
• Paper clips or small nails of different metallic objects,
• Biro-pen casing
• Staples.
What to do
1. Explore what happens if you place the materials listed above close
to a magnet. Come up with a table like this.

• A magnet attracts certain things but not others:
• A magnet attracts iron fillings, iron nails, office pins, staples, sewing
needles, safety pins. These are magnetic materials.A magnet
attract objects made up of iron, steel,nickel e.t.c
• On the other hand, a magnet does not attract things like plastic,
wood, paper, glass, copper and aluminum foil. They are non-magnetic
materials.

Table 15.1: Magnetic and non-magnetic materials

Self –Test 15.1
1. Name some magnetic materials found in your home.
2. Suppose you have dropped iron fillings in some salt or sugar,
explain how you can separate the two.
3. Give any four uses of magnets.
4. Explain how you can create magnetism using biropen case or
comb using your hair.
15.4 Magnetic field
Find out
The definition of a magnetic field.
Patterns or field lines at a magnet.

Activity 15.6 Investigating force of attraction of a magnet
What you need
• Permanent magnets of different types (horse-shoe and bar
magnets)
• White sheet of paper
• Iron fillings
What to do
1. Place the bar magnet and the horse-shoe magnet one at a time
below a white sheet of paper.
2. Sprinkle the iron fillings on the white paper. What do you
observe? Draw the pattern formed by the iron- fillings.
3. Now, bring two bar magnets with their north poles close to one
another below the piece of paper. Sprinkle the iron fillings. What
happens to the iron fillings?
4. Repeat step 4 above but this time with the north and south poles
of the two magnets facing one another.
Draw the pattern made by the iron fillings in each case above. Is there
any difference between the patterns? Why is this the case?

Magnetic field is the area around a magnet or materials that are
magnetic where magnetic force is experienced.

When two North poles of two bar magnets are brought together; their
magnetic fields interact with one another to form a pattern like the one
shown below.

However, when the North Pole and the South pole of two bar magnets
are brought together, the field lines formed are shown below.
15.5 Magnetic compass
Find out
The function of a magnetic compass and its uses.

Activity 15.7 Making a simple magnetic compass
What you need
A magnet, clear jar with some water, three needles, thread, pencil,
piece of Manila paper, tape clay or Plasticine.
What to do
1. Magnetize the needles by rubbing them against the magnet as
explained in Activity 15.5.
2. Tape the needles onto a piece of paper. Mark the paper with the
end with needle eye ‘N’ and the pointed part ‘S’.
3. Insert the third needle into clay or Plasticine. Balance the paper
with needles on top of the third needle as shown below.
4. Tap one end of the paper. Does the paper turn to its original
position? Why is this the case?
5. Remove the needle and fasten the magnet using a string onto the
pencil.
6. Put the pencil across the mouth of the clear jar with water as
shown below.
Watch as the magnet spin inside the clear bottle. Where does it
settle?
7. Disturb the jar by turning it. Note what happens to the magnet.
8. Look at the picture below. What is shown in the picture? How is
it useful in our lives?
9. Discuss the results of this experiment. Write short notes and do
a presentation to the rest of the class.
• The picture in Activity 15.6 above shows a magnetic compass.
• Magnetic compass is an instrument that uses magnetised steel bar
to indicate direction relative to the Earth’s magnetic poles.
• You earlier learnt that the Earth’s core is made up of magnetic
materials. This makes the Earth a huge magnet.
• Therefore, being a magnet, it has poles.
• When the magnetic compass is
placed at any point on the surface
of the earth, the steel bar rests with
its head pointing in the magnetic
north direction of the earth. Thus
the compass can be used to find or
locate direction of a place while on
the surface of the Earth.
15.6 Uses of magnets
Find out
The devices that we use in our daily life that use magnets.
Activity 15.8 Use of magnet
1. Look at the pictures below. What can you see in the pictures?
2. Discuss how magnets are used above objects.
Magnets are used almost everywhere in our lives. The things in the
pictures above show where magnets are used. Other uses include:
• Electric trains and roller coasters use electromagnets.
• Electromagnets are also useful in carrying heavy loads at the
port.
• Used in refrigerators to keep doors closed.
• They are used in TV screens, computers, telephones, tape recorders
and as magnetic strips in electronic cards.
• Used in speakers of radios to help in sound production.
• Used in constructing electric motors and generators.
• Used in making of electric bells.
• Used in separating mixtures involving magnetic and nonmagnetic
substances, for example iron fillings and flour.
• Used in making telegraph machines.
• Magnetic compass is used in showing or finding directions.
Self –Test 15.2
1. What is magnetic field?
2. State one important use of a magnetic compass.
3. Draw a diagram to show how iron fillings will be distributed
when placed on a paper covering a horse-shoe magnet.
4. Name four areas where magnets are used at home.
UNIT TEST 15
1. What is magnetism and how is it important in our lives?
2. Many materials found where we live are either magnetic or nonmagnetic.
Based on that information, fill the table below.
3. Draw a diagram to show magnetic field when unlike poles of two
bar magnets are brought close together.
4. Magnets can be temporary or permanent. What is the difference
between the temporary and permanent magnet?
5. What are magnets made of?______________________
6. In which of the following mixtures can the solids be separated by
use of a magnet?
A. Rice and husk.
B. Iron fillings and flour.
C. Flour and copper turnings.
D. Zinc and copper turnings.
7. Which of the following pairs of materials consists only of nonmagnetic
materials?
A. Steel spoon, iron nail.
B. Aluminum foil, a glass rod.
C. Nickel, cobalt.
D. Chromium, cobalt.
8. Make a simple temporary magnet at home and use it to separate
a mixture of iron fillings and flour.
9. What are some of the characteristics of magnets?
10. Give an example of a natural material that is magnetic.
11. Suggest ways in which you can make use of magnets in your
local environment.

Science and Elementary Technology

General

Unit 15 Magnetism

Unit 15 Magnetism

Table of contents