What is a magnet and how does it work?
A complete guide to the world of magnetism: from physical definition, through power grades, to industrial applications.
Wybierz kształt magnesu:
1. Basics of physics and magnet construction
A magnet is an object that generates a magnetic field, capable of attracting ferromagnets (e.g., iron, steel, nickel). We distinguish between permanent magnets and electromagnets. Modern neodymium magnets are the pinnacle of materials engineering – they are durable and do not lose power over time (the drop is only 1% per 10 years).
The operation of a magnet results from the ordered movement of electrons in atoms. In ferromagnetic materials (like iron, cobalt, neodymium), atoms combine into groups called domains. When these domains are aligned in one direction, the material acquires permanent magnetic properties. Every magnet has two poles: North (N) and South (S). Identical poles repel each other, while opposite poles attract.
Neodymium magnets are sintered ceramics (powder pressed in a magnetic field). Their composition is mainly neodymium (Nd), iron (Fe), and boron (B). Thanks to the sintering process, they obtain a domain crystal structure that maintains the magnetic field for decades. These are the strongest permanent magnets in the world.
Magnetism has fascinated people since antiquity (natural magnets – lodestone). The first compass was described in Europe in the 12th century. The real revolution came in 1984 when sintered neodymium magnets (NdFeB) were invented. This allowed for the miniaturization of electronics – without them, we wouldn't have today's smartphones.
2. Types, shapes, and materials
| Feature | Neodymium Magnet (NdFeB) | Ferrite Magnet (FeSr) |
|---|---|---|
| Strength (Induction) | Very high (approx. 10x stronger) | Low / Standard |
| Color | Silver (nickel coating) | Black / Dark gray |
| Corrosion resistance | Low (requires coating) | Excellent (does not rust) |
| Price | Higher | Very low |
| Max. temperature | Standard 80°C (option up to 230°C) | Standard up to 250°C |
A cylinder-shaped magnet (disc) is the most popular format. Usually axially magnetized (poles on flat surfaces). Ideal for joining objects and building separators. Covered with a Ni-Cu-Ni layer protecting against corrosion.
Plate magnets (blocks) are usually magnetized through the thickness. They are the basic building block of brushless motors (BLDC), generators, and belt separators. Their flat shape makes them easy to glue to surfaces.
A magnet in the shape of a ring, often with a hole for a screw (countersunk). Allows for easy screwing to a wall, wood, or plastic. Ideal for creating hangers and furniture closures. Note: do not tighten too much so it doesn't crack!
Ferrite magnet (black) is cheap and rust-resistant, but weak. Neodymium magnet (silver) is approx. 10x stronger, but more expensive and prone to corrosion (requires coating). Choose ferrite for simple applications, and neodymium where power counts.
3. Technical parameters, power, and durability
Remanence (Br): Magnetic remanence. Determines how strong a magnetic flux remains in the magnet after its saturation.
Coercivity (HcJ): The force needed to completely demagnetize the material. The higher it is, the more durable the magnet.
Curie temperature: The temperature above which a ferromagnetic material loses its magnetic properties irreversibly.
Gauss / Tesla: Units of magnetic induction. 1 Tesla = 10,000 Gauss.
The strongest permanent magnet is neodymium (NdFeB) in grade N52. It is a mixture of neodymium, iron, and boron. Used where extreme force is required with minimal size.
Symbols N38, N42, N52 indicate the energy class (Power). The higher the number, the stronger the magnet. N52 is approx. 35% stronger than N35. The letter 'N' indicates standard operating temperature up to 80°C.
Strength is affected by:
1. Air gap (rust/paint drastically weakens the hold).
2. Material (thin sheet metal on a fridge limits the magnet's power).
3. Direction (a magnet slid down holds only 15-20% of its nominal power).
1. Air gap (rust/paint drastically weakens the hold).
2. Material (thin sheet metal on a fridge limits the magnet's power).
3. Direction (a magnet slid down holds only 15-20% of its nominal power).
Standard neodymium works up to 80°C. Above this limit, it loses power. For work in heat (motors), high-temperature magnets (H, SH, UH) or resistant ferrites (up to 250°C) are used.
Under normal conditions, neodymiums are permanent (losing 1% power per 10 years). They can be destroyed by: exceeding the Curie temp., a strong opposing magnetic field, or corrosion (rust eats the magnet from the inside).
4. Practical application and safety
The application is huge: from separators in the food industry, through electric motors, to home knife holders and invisible clasps in handbags. Thanks to various shapes, such as cylindrical magnets or plate magnets, engineers can precisely design compact devices.
Magnetic holders are used for lifting loads. The steel housing focuses the field on one side, increasing the lifting capacity and protecting the brittle magnet from breaking.
Caution! Large neodymiums can crush fingers. People with pacemakers must maintain a distance (min. 50cm). Swallowing magnets by a child carries a risk of death. Keep away from electronics and payment cards.
Buy only in proven specialized stores like dhit.pl. Cheap magnets from auctions often have inflated parameters (e.g., N52 which is actually N35) or weak coating.