Chapter 2 of 8

All 8 chapters
  1. 1What magnets pull, readunderstood
  2. 2North and south poles, readunderstood
  3. 3Magnetic force through things, readunderstood
  4. 4Making a compass, readunderstood
  5. 5Electricity: safe and unsafe, readunderstood
  6. 6A simple circuit, readunderstood
  7. 7Conductors, insulators and switches, readunderstood
  8. 8Circuit drawings, readunderstood

S2.8.2 Chapter 2

North and south poles

Why do two magnets sometimes push each other away?

Your guess

Pick one before you read on. It is fine to be wrong.

Your guess

  • You picked A. Read on. At the end, the chapter comes back to your guess.

  • You picked B. Read on. At the end, the chapter comes back to your guess.

  • You picked C. Read on. At the end, the chapter comes back to your guess.

By the end you can

  • Show that like poles push apart and unlike poles pull together
  • Find the poles of a magnet using a second magnet

Hold two magnets close. Sometimes they jump together. Sometimes they push apart. Why?

A bar magnet has two ends called poles. A pole is where the pull is strongest. One pole is called north, or N. The other is called south, or S.

In our pictures, the N half is shaded with lines. The S half is plain.

Draw it first

Draw how two magnets act

  1. Three pictures, one under the other. First, a bar magnet with the pole N on one half and the pole S on the other half. Second, two magnets with unlike poles facing, with arrows toward each other, labelled attract. Third, two magnets with like poles facing, with arrows away from each other, labelled repel. Labels: N, S, attract, repel.NS

    1 Draw a bar magnet. Write N on one end and S on the other.

  2. Three pictures, one under the other. First, a bar magnet with the pole N on one half and the pole S on the other half. Second, two magnets with unlike poles facing, with arrows toward each other, labelled attract. Third, two magnets with like poles facing, with arrows away from each other, labelled repel. Labels: N, S, attract, repel.NSSNSNattract

    2 Draw two magnets with N facing S. Draw arrows toward each other. Write attract.

  3. Three pictures, one under the other. First, a bar magnet with the pole N on one half and the pole S on the other half. Second, two magnets with unlike poles facing, with arrows toward each other, labelled attract. Third, two magnets with like poles facing, with arrows away from each other, labelled repel. Labels: N, S, attract, repel.NSSNSNattractSNNSrepel

    3 Draw two magnets with N facing N. Draw arrows away from each other. Write repel.

Two poles that are the same are like poles. N and N are like. S and S are like. N and S are unlike.

To repel means to push away. Like poles repel. Unlike poles attract.

See it three ways

As a picture

Three rows. In each row, two poles are side by side, then a word. N and N: push apart. S and S: push apart. N and S: pull together. Labels: N, S, push apart, pull together.NNpush apartSSpush apartNSpull together

In words

Like poles push apart. Unlike poles pull together.

Only a magnet can push a magnet. Either pole pulls an iron nail that is not a magnet. It is never pushed.

Two rows. In each row a nail, labelled nail, has an arrow toward a bar magnet, and the word pulled is beside the magnet. In the first row the nail is near the N end of the magnet. In the second row it is near the S end. Labels: nail, N, S, pulled.nailNSpullednailSNpulled
A nail that is not a magnet is pulled by either pole.

You can find the poles of a magnet with a second magnet. The poles of the second magnet tell you which is which.

Try it

Find the poles with a second magnet

You need: two bar magnets, or two fridge magnets, two round pencils, a small piece of tape, a smooth table.

Be safe: Keep the magnets away from phones and bank cards. If you have no magnets, look at the result picture.

  1. Stick tape on one end of magnet A. Call that end N.
  2. Lay magnet B on the two pencils. It can roll.
  3. Hold the N end of A near one end of B. Do not touch.
  4. Does B roll away, or toward A?
  5. Now try the other end of B.

What you will see: One end of B rolls away from the N end of A. That end of B matches your N. The other end of B rolls toward A. It matches your S. Your N is only a name you chose. It may really be S. The rule still works. With round fridge magnets, flip one over. One face pulls. The other face pushes.

If you cannot try it, this is what happens.
Two bar magnets in a line. The left magnet has S on its left half and N on its right half. Its N end faces the right magnet. The right magnet has N on its left half and S on its right half. It rests on two round pencils. An arrow points to the right, away from the left magnet, labelled moves away. Labels: S, N, moves away.SNNSmoves away

A wrong idea many people have

Magnets only pull.

Why it feels right: A magnet pulls nails, clips and the fridge door. You never see it push them.

The test that breaks it: Hold two magnets close. Turn one around, so the other end faces the first. Before, they pulled together. Now they push apart.

What is true: Two magnets can pull or push. Only a magnet can push a magnet. An iron nail that is not a magnet is never pushed away.

Key words

pole
an end of a magnet, where the pull is strongest. N or S.
attract
to pull close. Unlike poles do this.
repel
to push away. Like poles do this.

Back to your guess

The answer is C: Magnets pull or push, by which ends meet.

Magnets can pull or push. It depends on which ends meet. Like poles push. Unlike poles pull.

Check yourself

Try each one before you look. A wrong answer tells you where to go next.

  1. Two N poles are held close. What happens?

    Tap your answer.

    1. Not this one. N and N are like poles. Like poles push apart. Only unlike poles pull together. Try another.

    2. Yes, that is right. Like poles repel.

    3. Not this one. Two magnets always act on each other when they are close. Try another.

    See the answer

    They push apart.

    Like poles repel.

    • If you chose A: N and N are like poles. Like poles push apart. Only unlike poles pull together.
    • If you chose C: Two magnets always act on each other when they are close.

  2. Look at the picture. What will the two magnets do?

    Two bar magnets end to end with a small gap. The left magnet has N on its left end and S on its right end. The right magnet has N on its left end and S on its right end. Labels: N, S.NSNS
    Tap your answer.

    1. Yes, that is right. The facing ends are S and N. Unlike poles pull together.

    2. Not this one. The ends that face each other are S and N. Those are unlike poles. They attract. Try another.

    3. Not this one. Different poles are the ones that pull. Magnets act on each other when they are close. Try another.

    See the answer

    They will pull together.

    The facing ends are S and N. Unlike poles pull together.

    • If you chose B: The ends that face each other are S and N. Those are unlike poles. They attract.
    • If you chose C: Different poles are the ones that pull. Magnets act on each other when they are close.

  3. One end of a magnet pulls the N end of another. What pole is that end?

    Tap your answer.

    1. Not this one. N and N push apart. A pull means the poles are unlike. Try another.

    2. Not this one. Only an S pole pulls an N pole. An N pole pushes it away. Try another.

    3. Yes, that is right. It pulls, so the poles are unlike. The other pole is S.

    See the answer

    S

    It pulls, so the poles are unlike. The other pole is S.

    • If you chose A: N and N push apart. A pull means the poles are unlike.
    • If you chose B: Only an S pole pulls an N pole. An N pole pushes it away.

  4. From an earlier chapter

    Which of these will a magnet pull?

    Tap your answer.

    1. Yes, that is right. A magnet pulls iron and steel.

    2. Not this one. Wood is not magnetic. Go to S2.8.1. Try another.

    3. Not this one. Foil is aluminium. A magnet does not pull it. Go to S2.8.1. Try another.

    See the answer

    A steel nail

    A magnet pulls iron and steel.

    • If you chose B: Wood is not magnetic. Go to S2.8.1.
    • If you chose C: Foil is aluminium. A magnet does not pull it. Go to S2.8.1.

  5. You have a magnet with N marked. How do you find the poles of a second magnet?

    See the answer

    Bring the marked N end near each end of the other. The end that is pushed away is N. The end that is pulled is S.

    Like poles push apart. Unlike poles pull together.

  6. Why do two magnets sometimes push each other apart?

    Tap your answer.

    1. Not this one. A pole is not always one thing. N pushes another N, but N pulls an S. Try another.

    2. Not this one. Size does not decide. Two magnets of one size push apart when like poles meet. Try another.

    3. Not this one. Unlike poles pull together. It is like poles that push apart. Try another.

    4. Yes, that is right. Two N poles push apart, and so do two S poles. Like poles repel.

    See the answer

    Like poles face each other.

    Two N poles push apart, and so do two S poles. Like poles repel.

    • If you chose A: A pole is not always one thing. N pushes another N, but N pulls an S.
    • If you chose B: Size does not decide. Two magnets of one size push apart when like poles meet.
    • If you chose C: Unlike poles pull together. It is like poles that push apart.

  7. Look at the picture. Hana turns one magnet right round. What do they do now?

    Two bar magnets end to end. The left magnet has N on its left end and S on its right end. The right magnet has N on its left end and S on its right end. Arrows point toward each other. The word under them is attract. Labels: N, S, attract.NSNSattract
    Tap your answer.

    1. Not this one. Turning a magnet round puts its other pole at the gap. The two facing poles are now alike. Try another.

    2. Yes, that is right. Turning one magnet puts a like pole at the gap. Like poles push apart.

    3. Not this one. Two magnets close together always act on each other. They pull or they push. Try another.

    See the answer

    They push apart.

    Turning one magnet puts a like pole at the gap. Like poles push apart.

    • If you chose A: Turning a magnet round puts its other pole at the gap. The two facing poles are now alike.
    • If you chose C: Two magnets close together always act on each other. They pull or they push.

  8. Look at the picture. A nail that is not a magnet sits by the S end. What does it do?

    A bar magnet with N on its left half and S on its right half. Close to its S end is an iron nail, labelled nail. Labels: N, S, nail.NSnail
    Tap your answer.

    1. Not this one. Only a magnet can push a magnet. A nail that is not a magnet is only pulled. Try another.

    2. Not this one. Both poles pull a nail. The S pole pulls it too. Try another.

    3. Not this one. A magnet pulls iron and steel, even when they are not magnets. That is how it lifts a nail. Try another.

    4. Yes, that is right. Either pole pulls an iron nail that is not a magnet. It is never pushed.

    See the answer

    It is pulled toward the S end.

    Either pole pulls an iron nail that is not a magnet. It is never pushed.

    • If you chose A: Only a magnet can push a magnet. A nail that is not a magnet is only pulled.
    • If you chose B: Both poles pull a nail. The S pole pulls it too.
    • If you chose C: A magnet pulls iron and steel, even when they are not magnets. That is how it lifts a nail.

  9. Which way finds the poles of a magnet, using a second magnet?

    Tap your answer.

    1. Not this one. A nail is pulled by both poles. It cannot show which end is N and which is S. Try another.

    2. Not this one. Both poles of a magnet pull about as hard. Strength does not tell N from S. Try another.

    3. Yes, that is right. Like poles push apart. The end pushed away from your marked N is also N.

    See the answer

    Bring a marked N end near each end. The end that is pushed away is N.

    Like poles push apart. The end pushed away from your marked N is also N.

    • If you chose A: A nail is pulled by both poles. It cannot show which end is N and which is S.
    • If you chose B: Both poles of a magnet pull about as hard. Strength does not tell N from S.

Keep it

Copy this into your exercise book.

A magnet has two poles, N and S. Like poles push apart. Unlike poles pull together. Only a magnet can push another magnet. An iron nail that is not a magnet is only ever pulled.

Draw: Two bar magnets with N and S ends. Arrows to show push and pull.

Reading with a child? A short page for the adult: what this chapter teaches and three questions to ask.

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