Exploring Magnets | CBSE Class 6 Science Notes

This note covers magnets and their shapes, magnetic and non-magnetic materials, magnetic poles, finding directions, magnetic compasses, making a needle into a magnet, attraction and repulsion, magnetic effects through materials, activities with magnets, and the care and storage of magnets.

What are magnets, and where do we use them?

A magnet attracts materials such as iron. Magnets can hold objects together, help us find directions, and move some objects without touching them. Exploring these effects begins with observing which objects a magnet attracts and how magnets behave near one another.

Natural and artificial magnets

Lodestones are naturally occurring magnets discovered in ancient times. Magnets used by sailors in the olden days were based on lodestones. Later, people found that pieces of iron could be made into magnets. Magnets are now made from different materials.

Artificial magnets are magnets made by people. Magnets found in school laboratories, pencil boxes, stickers and toys are artificial magnets. A magnet need not have the same shape as another magnet to show magnetic properties.

A bar magnet has the shape of a bar. A U-shaped magnet is shaped like the letter U, and a ring magnet has a ring shape. These names describe shapes, rather than different rules of magnetic behaviour.

Photograph: Magnets of different shapes (NCERT Class 6 Figure 4.2). The pictures show a straight bar magnet, a magnet bent into a U shape, and a ring magnet with a hole through its centre. Each is labelled with its shape name.

Familiar uses

Magnets help keep some pencil boxes and purses closed. A writing-board duster can also have a magnet. A magnetic compass is a device that uses a magnet to find directions. These uses introduce two useful properties: attracting certain materials and helping to identify directions.

How can we distinguish magnetic and non-magnetic materials?

Definition: Magnetic materials are materials attracted towards a magnet. Non-magnetic materials are materials not attracted towards a magnet. The distinction depends on how the material behaves when a magnet is brought near it.

Iron, nickel and cobalt are magnetic metals. Some of their combinations with other metals are also attracted towards magnets. Keep the word some: this statement does not classify every combination of metals as magnetic.

Predict, test and record

A prediction is what you expect to happen before a test. An observation is what you notice during the test. Keeping these separate lets you compare your expectation with the actual behaviour of each object.

1. Collect a magnet and several objects made of different materials.
2. Write down the name of each object and the material from which it is made.
3. Predict whether the magnet will attract each object before testing it.
4. Bring the magnet near the objects one at a time and observe which objects stick to it.
5. Record the result for each object and compare it with your prediction.

Some objects stick to the magnet, while others do not. Classify the materials from these observations. A prediction that turns out to be wrong is still useful because the test shows how the material actually behaves.

Attraction means a pull towards something. An object being attracted to a magnet shows that its material is magnetic. This observation alone does not establish that the object is itself a magnet; a piece of iron is also attracted.

Where are the poles of a magnet, and how can we investigate them?

The poles of a bar magnet are its two ends, where most iron filings stick. Iron filings are very small pieces of iron. Their distribution helps us compare attraction near the ends with attraction over the remaining part of the bar magnet.

Observing iron filings

1. Spread some iron filings over a sheet of paper.
2. Place a bar magnet over the filings.
3. Tap the paper and look carefully at the filings sticking to the magnet.
4. Compare the amount near the ends with the amount over the remaining part.

The maximum number of filings sticks near the ends, while very few stick to the remaining part. The filings do not cover the magnet uniformly. Most iron filings stick to the poles of a magnet of any shape.

Photograph: Iron filings sticking to a bar magnet (NCERT Class 6 Figure 4.4). The photograph shows dense bunches of iron filings around both ends of a bar magnet. Much less of the magnet's central part is covered by filings.

The two poles are the North pole, the end that points north when the magnet is freely suspended, and the South pole, the end that points south. Freely suspended means hanging so that the magnet can turn.

Reading a distribution of clips

For a bar magnet rolled over steel U-clips, consider three labelled positions: A is one end, B is the middle, and C is the other end. The following alternatives give numbers of clips at those positions.

Option (i) is the likely observation because both ends collect more clips than the middle. These are alternatives for this particular activity, not fixed numbers that every bar magnet must attract.

Note: Breaking a magnet does not produce a single pole. North and South poles always exist in pairs, even in the smallest piece. Each resulting magnetic piece has both poles.

How does a freely suspended magnet help us find directions?

A freely suspended magnet comes to rest along the north-south direction, the line joining the north and south directions. It does so because Earth itself behaves like a giant magnet. The magnet must be allowed to turn and then come to rest.

Testing the direction repeatedly

1. Tie a thread around the middle of a bar magnet and suspend it.
2. Adjust the thread until the magnet is balanced horizontally, with its length level.
3. Turn the magnet gently in the horizontal direction and allow it to stop moving.
4. Mark points on the ground, or on paper fixed to it, corresponding to the magnet's ends. Join the points with a line.
5. Give one end another gentle push. Wait for the magnet to stop and compare its direction with the marked line.

The magnet again rests along the same north-south line. Repeating the observation checks that the first resting direction was not simply an isolated result. The end pointing north is also called the North-seeking pole; the opposite end is the South-seeking pole.

The drawing shows a horizontal bar magnet hanging from a thread supported at a table. A sheet below the magnet provides a place to mark the positions corresponding to its ends.

See Fig. 4.5 in your NCERT textbook

Comparing a magnet with an iron bar

Repeat the activity with a small iron bar in place of the magnet. The iron bar does not always rest north-south; it can rest along any direction. This comparison gives a way to test whether a piece of metal is a magnet.

Watching where the Sun rises or sets gives an approximate idea of east or west. This can help locate the direction along which the suspended magnet rests. Keep this estimate separate from the magnet's repeated north-south alignment.

What is inside a magnetic compass, and how is it used?

A magnetic compass uses the directional property of a freely moving magnet. Its needle is a magnet shaped like a needle, rather than an ordinary unmagnetised pointer. When allowed to come to rest, the needle indicates the north-south direction.

Parts of the compass

A compass is usually a small circular box with a transparent cover, a cover through which the needle can be seen. A pin stands at the bottom of the box, and the magnetic needle is balanced on it so that it can rotate freely.

Below the needle lies the dial, the surface marked with directions. The needle's north-pointing end is usually painted red. The word usually matters: colour is a common indication, not a universal rule for every compass.

Finding directions step by step

1. Place the compass where you want to find the directions.
2. Allow the needle to come to rest along the north-south direction.
3. Gently rotate the compass box until the north and south markings on its dial line up with the needle.
4. Read the directions from the dial in this aligned position.

The freely turning needle and the printed dial have different roles. The needle settles along north-south; the box is turned to bring the direction markings into agreement with that needle. Reading the dial follows this alignment.

Note: A nearby magnet can turn a compass needle away from its earlier resting direction. The needle is itself a magnet and responds to the poles of another magnet brought close to it.

How can we make a simple compass from an iron needle?

An iron sewing needle can be magnetised, meaning made into a magnet, by stroking it with a magnet in a particular way. The magnetised needle can then turn with a floating cork to form a simple compass.

Materials and magnetisation

Collect an iron sewing needle, a cork piece, a bar magnet, a glass bowl and water. Place the needle on a wooden table. The important details are using the same pole, starting from the same needle end, and lifting the magnet for the return.

1. Place one pole of the bar magnet at one end of the needle.
2. Move this pole along the needle's length to the other end.
3. Lift the magnet, bring the same pole back to the starting end, and repeat the stroke.
4. Repeat the process at least 30 to 40 times.
5. Bring iron filings or steel pins near the needle. If they are attracted, the needle has become a magnet.

Part (a) shows a hand moving a bar magnet along a needle, with arrows indicating the movement. Part (b) shows a needle passing horizontally through a cork floating in a bowl of water.

See Fig. 4.7 in your NCERT textbook

Allowing the needle to turn

Pass the needle horizontally through the cork. Float the cork in the water so that the needle remains above the water level. Let it come to rest and note the directions in which its ends point.

Gently rotate the cork and wait for it to stop. Repeat this a few more times to check the direction. The magnetised needle acts as a compass when it is free to turn with the floating cork.

An older Indian device for navigation, finding the way during travel, was the matsya-yantra, also called machchh-yantra. It used a magnetised fish-shaped iron piece in a vessel of oil for navigation at sea, before the modern magnetic compass became widely used.

When do two magnets attract or repel each other?

Repulsion means a push away. When two magnets are brought near one another, their interaction depends on the poles facing each other. Like poles are two North poles or two South poles. Unlike poles are a North pole and a South pole.

Testing magnets on pencils

Use two bar magnets with their poles marked. Call the magnet placed on pencils magnet A and the magnet held in the hand magnet B. These letters identify the magnets; they do not name their poles.

1. Place the longer side of magnet A over 5 to 6 round pencils.
2. Bring one end of magnet B near one end of magnet A without letting the magnets touch.
3. Watch whether magnet A moves towards or away from magnet B.
4. Bring the other end of magnet B near the same end of magnet A and compare the movement.

Unlike poles attract, while like poles repel. The experiment shows that two magnets do not have to touch before one affects the other. The direction of movement changes when the facing poles change.

Applying this to a compass needle

Place a compass on a horizontal surface and let its needle rest. Bring a bar magnet's North pole close to the needle's North pole. The needle's North pole moves away. Bring the bar magnet's South pole close instead, and the needle's North pole moves closer.

This turning away from the earlier position is called deflection. Both attraction and repulsion of the compass needle follow the same pole relationships as the two bar magnets.

How can repulsion identify a magnet and its poles?

A magnet attracts a piece of iron, and it also attracts the unlike pole of another magnet. Therefore, attraction alone cannot distinguish a magnet from an ordinary iron bar. Both can be pulled towards a magnet during a test.

Comparing the responses

Replace one magnet in the interaction activity with an iron bar. Both ends of the iron bar are attracted by both the North and South poles of the magnet. By contrast, two magnets can repel when their like poles face each other.

Finding unmarked poles

Bring the North pole of a marked magnet near one end of an unmarked magnet. If that end is repelled, it is a North pole. If that end is attracted, it is a South pole. The other end of the unmarked magnet has the opposite pole.

Here, the tested object is already known to be a magnet. That information matters when using attraction to identify its pole. Without it, attraction could also be caused by an ordinary piece of iron.

Another method uses suspension. Hang the unmarked bar magnet freely, let it settle, and identify the north-pointing end. This is its North pole; the other is its South pole.

Note: If three identical-looking bars consist of two magnets and one ordinary iron bar, test pairs in different end arrangements. The pair that shows repulsion contains the two magnets. The remaining bar is the ordinary iron bar.

Can a magnetic effect act through non-magnetic materials?

A magnet can affect a compass needle even when a non-magnetic material is between them. To investigate this, first observe the needle's deflection with a nearby magnet. Then compare that observation with the result after inserting a material.

Keeping the arrangement in place

1. Place a compass on a horizontal surface and allow its needle to rest.
2. Bring a pole of a bar magnet near the needle and observe the deflection.
3. Without moving the magnet or compass, place a piece of wood upright between them, at a right angle to the table.
4. Observe the needle again and record whether the deflection changes appreciably.
5. Repeat with a cardboard sheet, a thin plastic sheet and a thin glass sheet.

There is no appreciable change in the needle's deflection when these materials are placed between the magnet and compass in this activity. Here, appreciable means large enough to be noticed. The conclusion is that the magnetic effect can act through non-magnetic materials.

Photograph: Compass needle and a magnet with a piece of wood in between (NCERT Class 6 Figure 4.10). The photograph shows a bar magnet and a compass on opposite sides of an upright piece of wood. The wood is labelled and stands between the magnet and the compass needle.

Keeping the magnet and compass undisturbed lets the comparison focus on the inserted material. Test wood, cardboard, plastic and glass in turn and record each observation. The finding concerns the magnetic effect passing through these non-magnetic materials; it does not make them magnetic.

Preserve the distinction between no appreciable change and a claim of absolutely no change under every possible arrangement. The observation supports the first statement and the conclusion drawn from this activity.

How can magnets be used in simple games and activities?

Attraction, repulsion and magnetic effects through materials can be explored through games. These activities connect a visible movement with the pole arrangement or magnetic material involved. The magnet can move some objects even when it does not touch them.

A maze and a paper clip

A maze is an arrangement of paths through which an object must be guided. Put steel balls in a cardboard maze tray and move a magnet beneath it. Magnetic attraction can guide the balls while the cardboard lies between them and the magnet.

A steel paper clip that has fallen into water can be picked out with a magnet while keeping the magnet and fingers dry. Bring the magnet near the outside of the glass and use its attraction to move the clip.

Matchbox cars and ring magnets

Two matchbox cars carrying magnets can move away from one another when like poles face each other. Identify the facing poles before predicting the motion. It is the repulsion of like poles that explains the cars moving apart.

If an upper ring magnet remains separated from a lower ring magnet on a stand, like poles facing each other could explain the separation. Turning one magnet over can bring unlike poles face to face so that the rings attract.

A hopping frog

A toy frog can be made using ring magnets fixed along a scale, or ruler, in an alternating North-South arrangement. A paper frog has another ring magnet glued at its base, together with a transparent, flexible plastic strip.

Slide the plastic strip carrying the frog over the scale to observe the frog hopping. The activity uses a moving magnet above a line of other magnets. Its movement gives another way to explore interactions between magnets.

Photograph: Two matchbox-magnet cars with like poles of the magnets facing each other (NCERT Class 6 Figure 4.14). The photograph shows two wheeled matchbox cars with bar magnets on top. The caption identifies the facing ends as like poles, which provides the information needed to predict repulsion.

How should magnets be marked, handled and stored?

Magnet markings help identify poles, but different magnets can use different markings. In some magnets, N means North pole and S means South pole. In some others, a white dot indicates the North pole.

Reading markings carefully

Sometimes the North pole is painted red and the South pole blue. Do not turn this into a rule that every red end must be north. An unmarked magnet can instead be tested using a marked magnet or by allowing it to hang freely.

Care and storage

Handle magnets carefully. Do not heat them, drop them or hammer them. Keep magnets away from mobile phones and remote controls. These precautions accompany the practical activities and apply when putting the magnets away afterwards.

1. Store bar magnets in pairs, placing unlike poles on the same side.
2. Keep a piece of wood between the two magnets.
3. Place two pieces of soft iron across the ends of the pair.
4. Keep the stored magnets away from mobile phones and remote controls.

In this storage arrangement, a North pole lies beside a South pole at each end of the pair. The wood goes between the long sides, while the soft iron pieces go across the ends. These are different parts of the arrangement.

Draw two parallel bar magnets with opposite pole arrangements. Label each North and South pole, put a wooden piece between the magnets, and show a soft iron piece across each end of the pair.

Glossary

• Magnet — An object that attracts magnetic materials and has North and South poles.
• Lodestone — A naturally occurring magnet on which early sailors' magnets were based.
• Artificial magnet — A magnet made by people, such as magnets used in pencil boxes and toys.
• Magnetic material — A material attracted towards a magnet, such as iron, nickel or cobalt.
• Non-magnetic material — A material not attracted towards a magnet, such as wood, plastic or glass.
• Iron filings — Very small pieces of iron used to investigate attraction near different parts of a magnet.
• North pole — The end of a freely suspended magnet that points towards the north direction.
• South pole — The end of a freely suspended magnet that points towards the south direction.
• Like poles — Two North poles or two South poles, which repel when brought close together.
• Unlike poles — A North pole and a South pole, which attract when brought close together.
• Magnetic compass — A direction-finding device containing a freely rotating magnet in the shape of a needle.
• Attraction — A pull towards another object, seen when unlike magnetic poles approach each other.
• Repulsion — A push away from another object, seen when like magnetic poles approach each other.
• Magnetisation — Making an object into a magnet, as when an iron needle is stroked with a magnet.
• Deflection — A change from the compass needle's earlier direction when a magnet is brought near it.

Common errors and misconceptions

• Misconception: Any object attracted by a magnet must itself be a magnet. Correct: An ordinary iron bar is also attracted. Repulsion can identify a magnet.
• Misconception: Iron filings stick equally over a bar magnet. Correct: Maximum filings stick near the ends, while very few stick to the remaining part.
• Misconception: Breaking a magnet separates its North and South poles. Correct: The poles always occur in pairs, including in the smaller pieces.
• Misconception: Any freely suspended iron bar must settle north-south. Correct: A freely suspended magnet does so; an ordinary iron bar can rest in any direction.
• Misconception: Two magnets attract whichever ends face each other. Correct: Unlike poles attract, whereas like poles repel.
• Misconception: Wood between a magnet and compass stops the magnetic effect. Correct: The activity shows no appreciable change in deflection with wood in between.
• Misconception: A compass needle's north-pointing end must always be red. Correct: That end is usually painted red; the colour is not a universal requirement.
• Misconception: Rub a needle back and forth with either pole to follow the compass-making method. Correct: Use the same pole from the same starting end, lifting it for the return.

Exam-style questions with model answers

Q1. Define a magnetic material and a non-magnetic material. Give one example of each. [2 marks]

1. A magnetic material is attracted towards a magnet. Iron is an example of a magnetic material.
2. A non-magnetic material is not attracted towards a magnet. Wood is an example of a non-magnetic material.

Q2. A bar magnet is rolled over steel U-clips. Position A is one end, B is the middle, and C is the other end. Four possible counts at A, B and C are (i) 10, 2, 10; (ii) 10, 10, 2; (iii) 2, 10, 10; and (iv) 10, 10, 10. Choose the likely option and explain the two features that support your choice. [3 marks]

1. Option (i) is the likely observation: 10 clips at position A, 2 clips at position B, and 10 clips at position C.
2. Positions A and C are the ends of the magnet. The larger counts at both ends agree with the greater collection of magnetic material near the poles.
3. Position B is the middle. Its smaller count agrees with very few iron filings sticking to the remaining part compared with the ends.

Q3. Describe an experiment using a bar magnet, thread and paper to show the direction in which a freely suspended magnet rests. Include a comparison with an ordinary iron bar. [5 marks]

1. Tie the thread around the middle of the bar magnet and suspend it. Adjust the thread so that the magnet hangs horizontally and can turn freely.
2. Turn the magnet gently in the horizontal direction, release it, and wait until it comes to rest before noting the positions of its ends.
3. On paper fixed below it, mark points corresponding to the two ends and join them. This line records the direction in which the magnet rests.
4. Give one end a gentle push and wait again. The magnet returns to the same north-south line, showing its repeated directional behaviour.
5. Replace the magnet with an ordinary iron bar and repeat. The iron bar can rest in any direction instead of consistently returning to north-south.

Q4. Using an iron sewing needle, a bar magnet, a wooden table, iron filings or steel pins, a cork, a glass bowl and water, explain how to make and check a simple compass. [5 marks]

1. Place the needle on the wooden table. Put one pole of the magnet at one end and move it along the needle to the other end.
2. Lift the magnet and return the same pole to the same starting end. Repeat this process at least 30 to 40 times, keeping the stroke direction unchanged.
3. Bring iron filings or steel pins near the needle. If the needle attracts them, it has become a magnet and can be used in the next step.
4. Pass the needle horizontally through the cork and float the cork in the bowl of water. Keep the needle above the water level.
5. Allow it to settle and note its direction. Gently rotate the cork, let it settle again, and repeat to check that the magnetised needle returns north-south.

Q5. You are given a bar magnet known to be a magnet but with unmarked poles, and another magnet with its North and South poles marked. Explain how to identify the unmarked poles, giving both possible test results. [3 marks]

1. Bring the marked magnet's North pole near one end of the unmarked magnet. Observe whether the tested end is attracted or repelled.
2. If that end is repelled, it is a North pole because like poles repel. The other end of the unmarked magnet is therefore South.
3. If that end is attracted, it is a South pole because unlike poles attract. The other end is therefore North. The tested object is already known to be a magnet.

Q6. Three identical-looking metal bars consist of two magnets and one ordinary iron bar. Without using another object, explain how to identify the two magnets. State why attraction alone is insufficient. [3 marks]

1. Bring pairs of bars close together, testing different end arrangements. Turn a bar around and repeat so that attraction in one arrangement does not end the test.
2. The pair that shows repulsion consists of the two magnets, because like magnetic poles repel. The remaining bar is the ordinary iron bar.
3. Attraction alone is insufficient because both poles of a magnet attract both ends of an ordinary iron bar. A magnet also attracts the unlike pole of another magnet.

Q7. A compass needle is deflected by a nearby bar magnet. Describe how to investigate whether this effect acts through wood, cardboard, plastic and glass. State the observation and conclusion. [4 marks]

1. Observe the initial deflection and keep the bar magnet and compass in their positions. Place a piece of wood upright between them without disturbing either.
2. Observe the needle again and record the result. Repeat by replacing the wood with cardboard, a thin plastic sheet and a thin glass sheet.
3. There is no appreciable change in the deflection when each of these materials is inserted in this activity.
4. Conclude that the magnetic effect can act through non-magnetic materials. The observation does not mean that the inserted materials have become magnets.

Q8. Two ring magnets lie on the same upright stand, with one above the other. The upper magnet remains separated from the lower magnet. Suggest a possible magnetic explanation, and explain how to make them come into contact without pushing either magnet towards the other. [3 marks]

1. A possible explanation is that like poles of the ring magnets face each other. The repulsion between them keeps the upper magnet from moving farther down.
2. Turn one of the ring magnets over so that its opposite pole faces the other magnet, changing the facing pair from like poles to unlike poles.
3. Unlike poles attract each other. This attraction allows the magnets to come together instead of remaining separated by the repulsion between like poles.

Key takeaways

• Magnetic materials are attracted towards magnets; iron, nickel and cobalt are examples, while wood, cardboard, plastic and glass are non-magnetic.
• Most iron filings collect near a magnet's poles, and North and South poles always occur together in pairs.
• A freely suspended magnet rests north-south, whereas an ordinary iron bar can come to rest in any direction.
• A compass uses a freely rotating magnetic needle; align the dial with the settled needle before reading directions.
• Unlike magnetic poles attract and like poles repel; repulsion distinguishes a magnet from an ordinary iron bar.
• A needle can be magnetised using repeated strokes with the same pole, starting at the same end each time.
• The compass activity shows no appreciable change in deflection through wood, cardboard, plastic and glass, demonstrating magnetic action through non-magnetic materials.
• Store bar magnets in pairs with unlike poles on the same side, wood between them, and soft iron across their ends.

Test yourself

What are lodestones?

Lodestones are naturally occurring magnets. Magnets used by sailors in the olden days were based on them.

What happens to the poles when a magnet is broken into smaller pieces?

Each magnetic piece has both a North and a South pole. Breaking does not produce a single magnetic pole.

Why does a freely suspended magnet rest north-south?

It rests along the north-south direction because Earth itself behaves like a giant magnet.

What happens when a bar magnet's North pole approaches a compass needle's North pole?

The needle's North pole moves away from the approaching North pole because like poles repel.

Why must the compass box be rotated after the needle settles?

The box is rotated to align the north and south markings on the dial with the needle before reading directions.

How can you check whether a stroked iron needle has become a magnet?

Bring iron filings or steel pins near it. Attraction of these objects shows that the needle has become a magnet.

What was the matsya-yantra used for?

It was used for navigation at sea. It contained a magnetised fish-shaped iron piece kept in a vessel of oil.

How should the result of inserting wood between a magnet and compass be described?

There is no appreciable change in deflection in the activity. This shows that the magnetic effect can act through non-magnetic material.