Exploring Magnets

Why This Matters

Have you ever felt a pencil box click shut by itself? Or seen a fridge sticker hold on with no glue? That little pull is a magnet at work.

A magnet is a special object that can pull some things towards it. It can pull them without even touching them. It feels a bit like magic. But it is not magic. It is science, and you can fully understand it.

Long ago, sailors had a big problem. At night they found their way using the stars. But on a cloudy night, the stars were hidden. Which way was north? Which way was home? They could get lost at sea.

Then people found a clever trick. A magnet, when left free to turn, always points the same way — north and south. With this trick they built a tiny tool called a compass. After that, sailors could find their way even on the darkest, cloudiest night.

In this chapter you will learn how a magnet works, why it points north–south, and how you can make a magnet of your own. Let us explore.

The Big Idea

A magnet is an object that pulls things made of iron (and a few other metals) towards it. Every magnet has two ends called poles — a North pole and a South pole — and the pull is strongest at these poles. Two magnets follow one simple rule: unlike poles attract (pull together) and like poles repel (push apart). And because the whole Earth acts like one huge magnet, a freely hanging magnet always turns to point north–south. That single fact is what makes a compass work.

Let’s Break It Down

What magnets are and their shapes

A magnet is an object that can pull certain materials, like iron, towards it. This pull is called attraction. To attract simply means to pull closer.

Some magnets are found in nature. Long ago, people discovered a special black stone that pulled bits of iron. This natural magnet is called a lodestone. These are called natural magnets.

Today we do not need to dig up special stones. We can make magnets ourselves from pieces of iron and other materials. A magnet made by people is called an artificial magnet (or a man-made magnet). The magnets in your school lab, in pencil boxes, in toys, and on fridge stickers are all artificial magnets.

Magnets come in many shapes. Here are the common ones:

• Bar magnet — shaped like a flat stick or a bar.
• U-shaped magnet — bent like the letter U (also called a horseshoe magnet).
• Ring magnet — shaped like a round ring with a hole in the middle.

The shape can change, but every magnet still behaves like a magnet. In this chapter we will mostly use a bar magnet, because it is the easiest to draw and to understand.

Magnetic and non-magnetic materials

Does a magnet pull everything? Let us find out.

Take a magnet and hold it near different objects, one at a time — an iron nail, a steel pin, a plastic comb, a wooden pencil, a rubber eraser, a glass bangle, a copper coin. Watch which ones jump to the magnet and stick.

You will see something interesting. Only some objects stick. The iron nail and the steel pin stick. But the plastic, wood, rubber, and glass do not stick at all.

Materials that are pulled by a magnet are called magnetic materials. Iron is the main magnetic material. Two other metals, nickel and cobalt, are also magnetic. (You do not need to memorise nickel and cobalt deeply — just know iron is the big one.)

Materials that are not pulled by a magnet are called non-magnetic materials. Plastic, wood, rubber, glass, cloth, and paper are all non-magnetic.

Here is a quick side-by-side to keep it clear:

Magnetic (sticks to a magnet)	Non-magnetic (does not stick)
Iron nail	Plastic comb
Steel pin (steel is mostly iron)	Wooden pencil
Iron key	Rubber eraser
Nickel, cobalt	Glass, paper, cloth

One thing surprises many students. Not every shiny metal is magnetic. A copper coin and an aluminium foil are metals, but a magnet does not pull them. So “metal” and “magnetic” are not the same thing. We will come back to this in Common Mistakes.

Poles of a magnet (North and South, strongest at the poles)

Now let us look more closely at the magnet itself. Is the pull the same everywhere on it?

Try this. Spread some tiny bits of iron — called iron filings — on a sheet of paper. Iron filings are just very small pieces of iron, like iron dust. Lay a bar magnet on top and gently tap the paper.

You will see the iron filings rush to the two ends of the magnet. Lots of filings cluster at each end. Very few stick to the middle.

This tells us something important. The pull of a magnet is strongest at its two ends. These two ends are called the poles of the magnet. Every magnet has exactly two poles:

• the North pole (we write it as N), and
• the South pole (we write it as S).

The invisible space around a magnet — where its pull and push can be felt — has a name too. It is called the magnet’s magnetic field. This field is strongest close to the poles and gets weaker as you move away from them. That is exactly why the iron filings crowd at the two ends: the magnetic field is strongest there.

Figure 4.1 below shows a bar magnet with its two poles, and the iron filings sticking thickly at the ends.

Tap to zoom

Here is a curious fact. Can you ever get a magnet with only one pole — say, just a North pole? No, you cannot. If you break a bar magnet into two pieces, each piece becomes a smaller magnet with both an N and an S pole. Break it again, and the same thing happens. No matter how small a piece you make, it always has two poles. A single lonely pole simply cannot exist.

Attraction and repulsion — like poles repel, unlike attract

So far one magnet has been pulling iron things. But what happens when two magnets meet? This is where magnets get really interesting.

Bring two bar magnets close. Sometimes they snap together. Sometimes they push away and refuse to meet, no matter how hard you try. Why the difference? It all depends on which poles are facing each other.

There is one simple rule, and it is the heart of this chapter:

• Unlike poles attract. A North pole and a South pole pull towards each other. (Unlike means different — N and S.)
• Like poles repel. Two North poles, or two South poles, push away from each other. (Like means same — N and N, or S and S.) To repel means to push apart.

You can remember it like this: opposites pull together, sames push apart. Figure 4.2 shows both cases.

Tap to zoom

Now here comes a clever idea — the part most students find surprising.

Repulsion (the pushing-apart) is the only sure test of a magnet.

Why? Think about it carefully. A plain iron bar is not a magnet, but a magnet still attracts it. So if you bring an object near a magnet and it gets pulled in, that does not prove the object is a magnet — it might just be a piece of iron being attracted.

But pushing-apart is different. Only a magnet can push another magnet away. A plain iron bar can never push a magnet away; it can only be pulled. So if two objects push each other apart, both of them must be magnets. That is why repulsion, not attraction, is the certain proof.

A magnet points north–south, and the compass

Now for the trick that helped lost sailors find their way home.

Tie a thread to the exact middle of a bar magnet, so it hangs flat and can turn freely. Give it a gentle spin and wait. When it stops, look where it points. Spin it again, wait again — it stops in the same line every time.

That line is the north–south line. The magnet always settles pointing north and south. The end that points to the north is called the North-seeking pole (the North pole, N). The end that points to the south is the South pole (S). That is actually why we named the poles “North” and “South” in the first place.

Figure 4.3 shows a bar magnet hanging from a thread, settled along the north–south direction.

Tap to zoom

Now try the same thing with a plain iron bar instead of a magnet. Hang it, spin it, wait. This time it stops in any direction — it does not care about north or south. So here is another handy test: only a magnet rests along north–south. An ordinary iron bar does not.

This north–south behaviour is so useful that people built a tool around it: the compass.

A magnetic compass is a small round box with a tiny magnet inside, shaped like a needle. The needle is balanced on a sharp pin so it can spin freely. Because the needle is a small magnet, it always settles pointing north–south. The box has the four directions marked on its face — North (N), South (S), East (E) and West (W).

To use it, you place the compass flat and wait for the needle to stop. Then you gently turn the box until the “N” on the dial lines up under the needle’s north end. Now every direction on the dial is correct, and you know which way is north, south, east, and west. Figure 4.4 shows a compass.

Tap to zoom

Making a magnet (the stroking method)

Here is the best part. You can turn a plain steel needle into a real magnet, all by yourself. The trick is called the stroking method, because you stroke (rub) the needle with a magnet.

Let us walk through it step by step.

Figure 4.5 shows these four steps one by one.

Tap to zoom

Two things matter a lot here. First, always use the same pole of the magnet. Second, always stroke in the same direction and lift the magnet back through the air. If you rub back and forth, you undo your own work and the needle will not become a magnet.

But why does rubbing turn the needle into a magnet? Here is the reason. Inside the steel needle are countless tiny magnets, far too small to see. Normally they point in all sorts of different directions, so their pulls cancel each other out — and the needle is not a magnet. Each time you stroke it with the same pole in the same direction, you nudge a few more of these tiny magnets to line up the same way. After many strokes, most of them point together. Now all their little pulls add up into one real magnet. This is also why rubbing back and forth spoils it: stroking the other way just knocks the tiny magnets out of line again.

This same trick is how a simple home-made compass is built. Once your needle is magnetised, push it through a small cork, float the cork in a bowl of water, and let it settle. It will point north–south — your very own compass.

The Earth is a giant magnet

We have said it twice now: a hanging magnet points north–south because the Earth is a giant magnet. Let us actually understand why that is true — nothing should be left as just a “given”.

Think back to the rule of two magnets: a magnet turns until its poles line up with another magnet near it. So if a hanging magnet always turns to face north–south, there must be another huge magnet making it do that. What is big enough? The Earth itself.

Deep inside, the Earth behaves as if it has a massive bar magnet running through it, roughly from top to bottom. So the whole planet is one enormous, gentle magnet. Your small hanging magnet feels the Earth’s magnetism and turns to line up with it — which lines it up north–south. Figure 4.6 shows this idea.

Tap to zoom

Here is the neat part. Look closely at Figure 4.6: the buried magnet is the other way round from what you would guess. Its south pole (S) sits up near the geographic North Pole, not its north pole. Why does that make sense? Remember our own rule from earlier in this chapter: unlike poles attract. The north end of your compass needle is pulled towards the north — so the thing pulling it up there must be a south pole. A confusing fact turns into a simple one: the compass points north because unlike poles attract.

So the compass is not magic at all. It is just one small magnet quietly lining up with one very, very big one — the Earth.

A quick note on uses, before we move on. Magnets are everywhere in daily life: they hold pencil-box and purse lids shut, stick notes to the fridge, keep cupboard doors closed, sort iron from rubbish at scrap yards, and sit inside speakers, electric motors, and many toys. And of course, the compass uses a magnet to help us find our way.

Common Mistakes

These are the slip-ups students make most often. Spot them now so you never fall for them.

Quick Check

Time to test yourself. Pick the best answer for each.

Practice Problems

Try each one yourself first. Then tap to check the full answer.

Easy

Medium

Challenge

Summary

• A magnet pulls (attracts) magnetic materials like iron towards it. Some magnets are natural (lodestone); most we use are artificial (man-made), in shapes like bar, U-shaped and ring.
• Magnetic materials (iron, nickel, cobalt, steel) are pulled by a magnet. Non-magnetic materials (plastic, wood, glass, paper, copper, aluminium) are not — so not every metal is magnetic.
• Every magnet has two poles: a North pole (N) and a South pole (S). The pull is strongest at the poles and weakest in the middle.
• Poles always exist in pairs. Breaking a magnet only makes smaller magnets, each with both poles. A single pole cannot exist.
• For two magnets: unlike poles attract (N and S pull together) and like poles repel (N–N or S–S push apart).
• Repulsion is the sure test of a magnet, because only a magnet can push another magnet away. Attraction alone is not proof.
• A freely hanging magnet points north–south, because the Earth itself acts like a giant magnet. A compass uses this to help us find directions.
• You can make a magnet from a steel needle by stroking it many times with one pole of a magnet, always in the same direction.

What’s Next

You now know how magnets pull, push, and point the way. Next, we get out a ruler and a clock. The next chapter is Measurement of Length and Motion. There you will learn how to measure how long things are and how fast they move — the careful measuring that all of science is built on. See you there!