Magnet Experiments at Home
Magnetism is one of the four fundamental forces of nature, intimately connected to electricity through Maxwell's equations. Every electric current produces a magnetic field, and every changing magnetic field produces an electric current. This relationship, called electromagnetism, is the basis of electric motors, generators, transformers, and wireless communication. The experiments below explore magnetic phenomena from simple field visualization to building working electromagnetic devices.
Map Magnetic Fields
Place a bar magnet on a flat surface and lay a sheet of paper over it. Sprinkle iron filings evenly on the paper and tap it gently. The filings align along the magnetic field lines, creating a visible map of the invisible field. You will see lines curving from one pole of the magnet to the other, densely packed near the poles where the field is strongest and widely spaced further away where it weakens.
Compare field patterns from different magnet configurations. Place two magnets with opposite poles facing each other (attracting) and observe how the field lines connect between them. Then flip one magnet so like poles face each other (repelling) and see how the field lines curve away, refusing to connect. Place a horseshoe magnet under the paper to see the concentrated field between its poles, which is why horseshoe magnets are stronger for gripping than bar magnets of the same material.
Use a small compass to trace field lines more precisely. Place the compass at various points around a bar magnet and mark the direction the needle points. Connect the marks to draw field lines. The compass needle is itself a small magnet that aligns with the local field direction, just as it aligns with Earth's magnetic field when used for navigation.
Test Magnetic Materials
Not all metals are magnetic, and not all magnetic materials are metals. Test household objects by holding a magnet near them and observing whether they are attracted. Iron, steel, nickel, and cobalt are ferromagnetic, meaning they are strongly attracted to magnets and can be magnetized themselves. Aluminum, copper, brass, gold, silver, glass, plastic, and wood are not attracted to permanent magnets under normal conditions.
Classify your test objects into three categories. Ferromagnetic materials are strongly attracted and stick to the magnet. Paramagnetic materials (like aluminum) show extremely weak attraction detectable only with sensitive instruments, essentially non-magnetic for practical purposes. Diamagnetic materials (like copper and bismuth) are actually very weakly repelled by magnets, though this effect is too subtle to observe with household magnets.
Test whether a magnet can influence non-magnetic materials indirectly. Place a paperclip on a table and bring a magnet close underneath. The paperclip jumps to the magnet through the table, demonstrating that magnetic fields pass through non-magnetic materials like wood. Try different thicknesses of material between the magnet and paperclip to determine how distance and barriers affect the magnetic force.
Build a Compass
Magnetize a sewing needle by stroking it in one direction (not back and forth) along a permanent magnet about 50 times. Each stroke should go from the eye end to the point, lifting the magnet away before returning for the next stroke. This aligns the magnetic domains within the needle's iron, converting it into a weak permanent magnet.
Float the magnetized needle on water by placing it on a small piece of cork, a leaf, or a thin slice of wine cork. The floating needle rotates freely and aligns itself with Earth's magnetic field, pointing approximately north-south. Mark which end points north, as this is now the north-seeking pole of your compass needle.
Compare your compass to a commercial compass to verify accuracy. Bring various magnets near your floating needle to observe how external magnetic fields override Earth's relatively weak field. Move the magnets to different positions around the needle and watch it track the strongest nearby field source. This explains why compasses become unreliable near iron structures, electric motors, and electronic devices that generate their own magnetic fields.
Explore Poles and Forces
Every magnet has two poles: north and south. Like poles repel each other, and opposite poles attract. Demonstrate this by suspending one bar magnet from a string so it hangs freely, then bring another magnet close. Approach with the opposite pole and the hanging magnet swings toward it (attraction). Approach with the same pole and it swings away (repulsion). The force is mutual: both magnets experience equal and opposite forces, consistent with Newton's third law.
Investigate how magnetic force changes with distance. Stack small disc magnets and determine how many paperclips each stack can hold from different distances. Or suspend one magnet and measure how close you must bring another before the suspended magnet begins to move. You will find that magnetic force decreases rapidly with distance, following an inverse cube law for dipole fields, meaning doubling the distance reduces the force to one-eighth.
Try to isolate a single magnetic pole by breaking a magnet in half. Each half immediately becomes a complete magnet with both north and south poles. No matter how small you break the pieces, each fragment has both poles. This is a fundamental property of magnetism: isolated magnetic monopoles have never been observed in nature, unlike electric charges which can exist as isolated positive or negative particles.
Build an Electromagnet
Wrap insulated copper wire tightly around a large iron nail, making as many turns as possible in a neat coil. Leave about 15 cm of wire free at each end. Strip the insulation from the wire ends and connect them to a D-cell battery (or two in series for a stronger effect). Current flowing through the wire coil creates a magnetic field, and the iron nail concentrates and amplifies this field, creating an electromagnet.
Test your electromagnet by picking up paperclips, staples, or small nails. Count how many it can hold. Then disconnect the battery and observe that the nail loses most of its magnetism, dropping the objects. This controllability is what makes electromagnets useful, unlike permanent magnets, they can be turned on and off and their strength can be varied by changing the current.
Experiment with variables that affect electromagnet strength. Add more wire turns (keeping everything else the same) and count paperclips again. Use two batteries in series to increase current and test again. Try different core materials: an iron nail, a steel bolt, a wooden dowel, and no core at all. The iron core dramatically increases field strength because iron's ferromagnetic properties concentrate the field lines. Without a core, the coil alone produces a much weaker field. This experiment teaches the three factors controlling electromagnet strength: number of turns, current, and core material.
Demonstrate Electromagnetic Induction
Michael Faraday discovered in 1831 that a changing magnetic field induces an electric current in a nearby conductor. You can replicate this foundational experiment. Wind 50 to 100 turns of thin insulated wire around a cardboard tube to create a coil. Connect the wire ends to a sensitive multimeter set to the millivolt DC range (or a galvanometer if available).
Push a strong bar magnet or stack of neodymium magnets into the coil quickly and observe the multimeter reading. It should register a small voltage while the magnet is moving. Pull the magnet out and the voltage reverses polarity. If you hold the magnet still inside the coil, no voltage is produced because induction requires a changing magnetic field, not merely the presence of one.
This is how electrical generators work at every scale, from bicycle dynamos to power plant turbines. The generator spins magnets past coils of wire (or coils past magnets), and the changing magnetic field induces current in the wire. Every watt of electricity you use, whether from coal, gas, nuclear, wind, or hydroelectric sources, is produced by electromagnetic induction, the same principle you just demonstrated with a coil of wire and a magnet in your kitchen.
Magnetism and electricity are two aspects of the same fundamental force. Understanding their connection through hands-on experiments reveals the operating principles behind motors, generators, and most of the technology that powers modern civilization.