◄Unit 14 Energy managementUNIT:16 States of matter►

Unit 15 Magnetism

  • Unit 15 Magnetism

    1. Study the pictures below

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    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.

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    b) Artificial magnets

    These are magnets made by human beings from magnetic materials.

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    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.

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    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?

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    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?

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    2. Suspend one bar magnet using a string as shown below

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    3. Bring the north pole of the second magnet near the south pole

    of the suspended magnet. What happens?

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    4. Bring the north pole of the second magnet close to the north

    pole of the first magnet. What happens?

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    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.
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    • 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
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    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.

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    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.

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    However, when the North Pole and the South pole of two bar magnets

    are brought together, the field lines formed are shown below.

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    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’.

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    3. Insert the third needle into clay or Plasticine. Balance the paper

    with needles on top of the third needle as shown below.

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    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.

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    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?

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    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.h
    • 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?

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    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.

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    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.

    ◄Unit 14 Energy managementUNIT:16 States of matter►