Chapter 13 — Fun with Magnets

What is a magnet?
A magnet is an object that produces an invisible force called a magnetic field and can attract certain metals such as iron, nickel and cobalt. Magnets are not all the same: some occur in nature while others are made by people. Natural magnets, such as lodestone, were used long ago to show properties of magnetism. Man-made magnets include bar magnets, horseshoe magnets, disc magnets and tiny magnets used in small motors and toys. The attractive effect of a magnet can be felt without touching the other object; this is because the magnet acts at a distance through its magnetic field.

We identify a magnet by simple tests. For example, a magnet can pick up small iron objects like paper clips and pins. A magnet will not pick up non-magnetic objects like a wooden matchstick or a plastic bead. Magnets also interact with each other: they may attract or repel depending on how they are held. These behaviours show that magnets have special ends where the magnetic influence is stronger; later we call these ends poles. Magnets are very useful because they allow us to hold, move or separate metal objects in a clean and contactless way. In classrooms and homes, magnets are found in toys, fridge magnets, magnetic catches and small electrical devices. By observing and experimenting, students learn that magnetism is a simple and powerful physical property which links to technology and nature alike.

Poles of a magnet
Every magnet has two ends known as poles where the magnetic effect is strongest. These ends are called the north-seeking pole (N) and the south-seeking pole (S). The name north-seeking comes from the observation that the end of a free magnet points towards the north when allowed to rotate; this helped early navigators. The poles are always found in pairs — a single isolated pole does not exist in ordinary magnets. If you cut a magnet into two pieces, each piece becomes a complete magnet with its own north and south poles. This shows that magnetism is due to the arrangement of tiny regions inside the material rather than a single pole being present.

Poles explain attraction and repulsion between magnets. Like poles repel each other: N repels N and S repels S. Unlike poles attract: N attracts S. You can test this by bringing different ends near each other and watching whether they push apart or pull together. The strength of interaction is strongest when poles are close. In many applications engineers place poles close together or design magnet shapes so poles face where forces are needed. For example, horseshoe magnets bring poles near to lift heavier objects. Understanding poles also helps when using a compass: the north-seeking end of the compass is actually attracted to the geographic north because of Earth's magnetic characteristics. Simple experiments with labeled poles help students link observed motion to the underlying concept of poles and field direction.

Magnetic and non-magnetic materials
Materials behave differently when brought near a magnet. Magnetic materials are those that are attracted by a magnet; common examples include iron, steel (an alloy of iron), nickel and cobalt. Non-magnetic materials do not show attraction under ordinary conditions; these include wood, plastic, glass, paper, copper and aluminium. To find out whether a material is magnetic, we use a simple test: bring a strong magnet near small samples and see which ones move towards it. This hands-on test is useful for sorting and separating materials in everyday tasks.

The reason some materials are magnetic lies in their internal structure. In magnetic materials many tiny regions called domains have their magnetic directions aligned or can be aligned easily when exposed to a magnet. When these domains line up, the whole piece shows a net magnetic effect and is attracted. In non-magnetic materials the domains either do not exist in the same way or do not align, so no attraction is seen. Some metals such as copper and aluminium conduct electricity well but are not magnetic under normal conditions. Stainless steel can be magnetic or not depending on the mix of metals in it; this is why some steel utensils stick to a magnet while others do not.

A classroom activity can help make these ideas clear. Collect small samples of various objects — a nail, a safety pin, a coin, a paper clip, a plastic button and a wooden splint. Predict which ones are magnetic and then test with a magnet. Record results in a table with columns: Object, Material, Predicted (Yes/No), Observed (Yes/No). Discuss why some predictions were wrong. Another useful exercise is to separate mixed sand and iron filings using a magnet: move a magnet over the mixture with a sheet of paper so the filings are attracted and lifted away. Such activities build careful observation and link simple tests to material properties.

Making a magnet
Some pieces of metal can be converted into magnets by changing the arrangement of their internal tiny magnetic regions. One common classroom method is stroking: take a clean piece of soft iron or a steel needle and stroke it many times with one pole of a strong bar magnet in the same direction. This repeated stroking aligns the internal regions so that the piece becomes a magnet. It usually becomes a temporary magnet and can pick up light iron objects like paper clips. The direction of stroking matters: always stroke from one end to the other in the same direction rather than back and forth.

Another method uses electricity. If we wrap insulated copper wire around an iron rod and pass a direct electric current through the coil, the iron becomes magnetised and acts as an electromagnet. The strength of this electromagnet depends on the number of turns of the coil and the current through it. When current stops, the magnetism usually disappears so the effect is controlled by switching the current on and off. Heating or hammering a magnet can destroy or reduce its magnetism because these actions disturb the alignment of the internal regions. These simple ways of making a magnet show students how magnetism can be produced and controlled, and why some magnets last longer than others depending on material and treatment.

Temporary and permanent magnets
Magnets can be classified by how long they keep their magnetism. Permanent magnets keep most of their magnetic strength for a long time and are made from materials that resist random disturbances of their internal regions. Examples include alnico and ceramic magnets used in toys, fridge magnets and some motors. Permanent magnets are useful where a steady magnetic field is needed without continuous power. They are made by special processes that align magnetic regions and then lock them in place.

Temporary magnets show magnetic behaviour only while they are in the presence of a stronger magnetic field or an electric current. Soft iron is a typical temporary magnet: when it is inside a coil with electric current, it becomes magnetic, but it loses magnetism once the current is switched off. Electromagnets are an important kind of temporary magnet because their magnetism can be turned on and off by controlling current. This makes them useful in devices like electric bells, relays and cranes for scrap metal. Understanding the differences helps us choose the right type of magnet for a job: if we need a magnet only sometimes, an electromagnet is best; if we need continuous attraction without power, a permanent magnet is chosen. Classroom tasks comparing how long different materials keep magnetisation give real insight into these categories.

Magnetic field and field lines
Around every magnet there is a space where the magnetic force can act; this region is called the magnetic field. We cannot see the field directly, but we can show its pattern with small iron filings or by moving a compass around the magnet. When iron filings are sprinkled on paper placed over a magnet, they arrange themselves along curved paths. These paths are called magnetic field lines. Field lines give us a way to represent how the magnetic field looks: they come out from the north pole of a magnet and enter the south pole. The density of field lines indicates the strength of the field — lines close together mean a stronger field.

Field lines have rules: they never cross each other and they form closed loops, going through the magnet inside from the south pole back to the north pole. For a bar magnet the external lines are curved arcs that connect the poles; for two magnets close together the lines change shape to show attraction or repulsion. A compass needle placed at different points aligns tangent to the local field line. By tracing compass directions or using filings we can create a map of the field in two dimensions. This mapping helps students visualise an invisible force and explain why forces act in certain directions. Drawing and interpreting field lines is a key skill at this level and supports later ideas in electromagnetism and forces at a distance.

Using a compass
A compass is a simple and useful instrument built from a small magnetised needle that can rotate freely on a pivot. The needle aligns itself with the local magnetic field and therefore shows directions. In everyday use the compass needle points approximately towards the Earth’s geographic north because the Earth behaves like a big magnet. The end of the needle that points towards geographic north is called the north-seeking end. A compass helps locate directions on the ground and is very useful for walking, map reading and basic navigation exercises in school.

To use a compass correctly, place it on a flat and non-metallic surface away from large metal objects or electric wires which could disturb the reading. Wait until the needle settles and then match the needle direction with the compass dial to read North, East, South and West. If you bring a strong magnet close to the compass, the needle will turn to align with the magnet’s field instead of Earth’s field; this demonstrates how local magnets influence the needle. Students can experiment by placing a bar magnet at different positions near the compass and noting the angle of deflection. These activities help learners understand both how a compass works and how magnetism can be used to find direction in practical situations such as field trips or simple mapping tasks.

Earth as a magnet
Earth behaves like a giant magnet surrounded by a magnetic field that extends into space. This planetary magnetic field is produced by moving electric currents in the molten iron of the outer core and by complex geological processes. A compass needle points roughly towards the magnetic north because it aligns with Earth’s magnetic field. The magnetic poles of Earth are not precisely at the geographic poles and they slowly move over time. The difference between geographic north and magnetic north at a location is called magnetic declination, and it is important for accurate navigation.

Earth’s magnetic field does more than point a compass. It protects the planet by deflecting charged particles from the Sun, which would otherwise strip away parts of the atmosphere and harm life. Many animals, such as migratory birds, use the magnetic field to find their way during long journeys. Simple classroom activities can show Earth’s magnetic effect: for example, a compass will point north even when far from other magnets, and a freely suspended magnet aligns with Earth’s field. Understanding Earth as a magnet connects local experiments with a global phenomenon, and it explains why compasses have been vital for sailors and explorers. Students learn that magnetism is not only a laboratory idea but also a large-scale force shaping life and travel on Earth.

Attraction and repulsion experiments
Simple experiments help us understand how magnets push and pull. One clear activity is to use two bar magnets and bring their ends close, testing different end combinations: N near S, N near N, and S near S. Record whether the magnets attract or repel. This shows the rule: unlike poles attract and like poles repel. Another activity is to suspend a magnet by a thread so it can rotate freely; then bring another magnet close and observe how the suspended magnet turns. The suspended magnet will align so that opposite poles face each other or will swing away if like poles are near. This experiment helps show not just the presence of force but its direction.

You can also compare the strength of magnets by measuring how many paper clips each can pick up. Place a magnet under a sheet or just touch directly and add paper clips one by one until it can lift no more. Different shapes and sizes of magnets show different lifting abilities. Testing a strong magnet and a weaker one gives an idea of field strength and limits of attraction. For safety, do experiments on a wooden or plastic table away from sensitive electronics. Recording observations in a table and drawing simple diagrams of the setup promotes scientific thinking and helps explain why devices such as magnetic locks or motors behave the way they do.

Magnetic materials in daily life
Magnets are part of many everyday tools and machines and their use affects how we store, move and use objects. Refrigerator magnets hold reminders and drawings on doors and are examples of small permanent magnets. Loudspeakers and earphones use magnets with coils: when electric current flows through the coil, it interacts with the magnet to move the speaker cone and create sound. Electric bells and some relays use electromagnets: when current passes through a coil, a soft iron core becomes magnetic and pulls a striker to ring the bell or close a switch. Large electromagnets in scrap yards lift heavy pieces of metal and are switched off when the load must be released.

There are many more applications. Magnetic strips on cards store information in banks and stores (though modern cards also use chips); magnetic storage once used in cassette tapes and computer hard disks records information by changing tiny magnetic regions. In medicine, MRI scanners use very strong magnets to make images of the body. Magnets are also inside small DC motors used in toys and appliances where magnetic forces help spin the rotor. Even simple devices like magnetic catches on cupboard doors and magnetic clasps on bags use attraction to hold parts together. Understanding these uses helps students relate magnetism to technology and everyday work. It also raises practical questions like why some materials are chosen (magnetic steels) and why electromagnets are preferred when controlled magnetism is needed. Discussing advantages, limitations and safe handling of these devices brings real-world context into science lessons.

Care and safety with magnets
Magnets can be very useful but they must be used safely and carefully. Strong magnets can damage electronic devices such as mobile phones, computers and credit cards because their magnetic fields can alter electronic components or erase magnetic data. Therefore keep strong magnets away from such devices. Small magnets are a choking hazard and can be particularly dangerous if swallowed: if more than one magnet is swallowed they can attract each other inside the body and cause severe damage to tissue. Always store small magnets out of reach of children and use them only with adult supervision.

Physical hazards from magnets include pinching and breaking. When two strong magnets snap together they can pinch skin or shatter into sharp pieces. Store strong magnets with spacers, or stack them with opposite poles facing to reduce sudden attraction. Avoid heating, hammering or dropping magnets as these actions can demagnetise them or cause cracks. For experiments involving iron filings, wear eye protection and work on a tray; filings stick to skin and clothes and can enter eyes. When working with coils and batteries follow electrical safety: avoid short circuits, use low voltage batteries and switch off when not in use. Teach students to clean up filings carefully, to label magnet storage boxes, and to report any swallowed or injured items to an adult immediately. These rules protect students and equipment and make classroom activities safe and enjoyable.

Interesting facts about magnets
Magnets have fascinated people for thousands of years and many surprising facts are easy to share in class. Natural magnetic stones called lodestones were known in ancient times and helped sailors find direction long before modern instruments. The Earth itself behaves like a huge magnet and its magnetic poles slowly move over time; scientists measure this movement and update navigational maps. Some living creatures can sense magnetic fields: migratory birds, sea turtles and certain bacteria use magnetism to guide their long journeys or to orient themselves. These biological uses show that magnetism is important beyond human technology.

Modern magnets include very strong materials called rare-earth magnets such as neodymium, which are small but much more powerful than older ceramic magnets. These strong magnets enable compact motors in devices like drones and earphones. Magnetic technologies are central to many fields: MRI machines in hospitals use very strong magnets to produce detailed images of tissues without surgery; maglev trains use magnets for levitation and propulsion to run smoothly at high speed with low friction; and computer hard disks store vast amounts of information by tiny magnetic regions. Research continues to find better magnetic materials, safer uses and more energy-efficient devices. Sharing such facts helps students see how a simple property of materials connects to ancient navigation, animal behaviour and cutting-edge technology, encouraging curiosity about science and engineering.

Demonstrations: iron filings and compass mapping
Two demonstrations make magnetic fields visible and help students learn to record observations. For iron filings, place a magnet under a sheet of paper and sprinkle iron filings evenly on top. Gently tap the paper so filings can move and settle along lines that reveal the magnetic field. The filings form curved patterns that are dense where the field is strong and sparse where it is weak. This method is useful for showing the field of a bar magnet, a horseshoe magnet or two magnets interacting. Always take safety precautions: wear goggles if needed and keep filings away from the face.

Compass mapping is a safe and accurate way to plot field direction. Place a magnet on a flat surface and move a small compass to several positions around it. At each position mark the direction the needle points on the paper and draw an arrow. Connect nearby arrow points smoothly to sketch the field lines. By repeating the pattern at many points a clearer map emerges. Students can compare the compass map with the iron filings pattern to see that both methods show the same field shape. These demonstrations teach careful measurement, recording and interpretation. They also prepare students to think about invisible fields by creating visible diagrams and written explanations of what they observe.

Revision and simple projects
Revision of the unit helps fix the main ideas: what magnets do, poles and their interactions, magnetic and non-magnetic materials, how to make magnets, magnetic fields and the role of Earth’s magnetism. Practical projects deepen understanding and give students a chance to plan experiments, record data and explain results. Small projects are inexpensive and safe and can be done at home or in school under supervision. They encourage curiosity and the habit of scientific observation.

Project ideas include making a simple compass using a magnetised needle balanced on a cork floating in water, building an electromagnet with insulated wire, a nail and a battery to test lifting power, or constructing a paperclip chain to compare magnet strengths. For the floating compass project, magnetise a needle by stroking it with a bar magnet, place the needle on a small piece of cork and float it in a bowl of water; mark the direction it points and compare with a real compass. For the electromagnet project, wind different numbers of turns of insulated wire around an iron nail, connect to a battery and count how many paper clips the nail lifts; change the number of turns or use more batteries and record the change. Students should write clear steps, draw labeled diagrams, tabulate data (for example number of clips lifted vs number of turns) and state conclusions such as how field strength depends on coil turns and current. Discuss sources of error (poor connections, damaged wire insulation) and suggest improvements (use more turns, better contact). Presenting results to the class and answering questions helps build confidence and scientific communication skills. These projects combine observation, measurement and explanation to make the learning active and memorable.