Frequently Asked Questions About Magnets & Magnetism
Here are answers to many common questions that people have about magnets and magnetism regarding the history, magnetic materials, magnetic properties, magnetic orientation, magnetic poles and more. For more technical info about these areas, visit our Magnetics-101-Design Guide.
- 1.0 History
- 2.0 The Basics
- 3.0 Magnetic Strength
- 4.0 Magnetic Field
- 5.0 Magnetic Poles
- 6.0 Magnetic Flux
- 7.0 Magnetic Orientation
- 8.0 Magnetic Characteristics
- 9.0 Magnetic Properties
- 10.0 Magnet Operating Temperatures
- 11.0 Machining Magnets
- 12.0 Magnetic Assemblies
- 13.0 Handling & Storage
- 14.0 Magnetic Resources
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1.0 A BRIEF HISTORY
The ancient Greeks and Chinese discovered that certain rare stones, called lodestones, were naturally magnetized. These stones could attract small pieces of iron in a seemingly magical way, and were found to always point in the same direction when allowed to swing freely, suspended by a piece of string, or floating on water. Early navigators used these magnets as rudimentary compasses to help them determine their direction while at sea.
The word "magnet" comes from Magnesia, a district in Thessaly, Greece where it is believed that the first lodestone was mined.
Over the years, magnets have evolved into the high-strength materials we have today. It was discovered that by creating alloys of various materials, one could create similar effects to those found in natural lodestone rocks, and increase the level of magnetism.
However, it was not until the 18th century that the first man-made magnets were created. Progress in creating stronger magnetic alloys was very slow until the 1920s when alnico magnet materials (an alloy of nickel, aluminum and cobalt) were formulated. Ferrite magnets were developed in the 1950s and rare-earth magnets in the 1970s. Since then, the science of magnetism has grown exponentially, and extremely powerful magnetic materials have made miniature and powerful devices possible. top
2.0 THE BASICS
What is a magnet?
Magnets can be made by placing a magnetic material, such as iron or steel, in a strong magnetic field. Permanent, temporary, and electromagnets can be produced in this manner.
The atoms forming materials that can be easily magnetized such as iron, steel, nickel, and cobalt are arranged in small units, called domains. Each domain, although microscopic in size, contains millions of billions of atoms and each domain acts like a small magnet. If a magnetic material is placed in a strong magnetic field, the individual domains, which normally point in all directions, will gradually swing around into the direction of the field. They also take over neighboring domains. When most of the domains are aligned to the field, the material becomes a magnet. top
Domains before magnetization
Domains after magnetization
What does a magnet do?
Magnets do the following things:
- Attract certain materials, such as iron, nickel, cobalt, certain steels and other alloys.
- Exert an attractive or repulsive force on other magnets (opposite poles attract, like poles repel).
- Have an effect on electrical conductors when the magnet and conductor are moving in relation to each other.
- Have an effect on the path taken by electrically charged particles traveling in free space.
Based on these effects, magnets transform energy from one form to another, without any permanent loss of their own energy. Examples of magnet functions are:
- Mechanical to mechanical, such as attraction and repulsion.
- Mechanical to electrical, such as generators and microphones.
- Electrical to mechanical, such as motors, loudspeakers, charged particle deflection.
- Mechanical to heat, such as eddy current and hysteresis torque devices.
- Special effects, such as magneto-resistance, Hall effect devices, and magnetic resonance. top
How are magnets made?
Modern magnet materials are made through casting, pressing and sintering, compression bonding, injection molding, extruding, or calendaring processes. Once manufactured, magnets often need to be further processed by grinding or other machining processes, and then assembled into a next level assembly. Visit our manufacturing and assembly page to learn more about our custom machining and assembly capabilities. top
Are there different types of magnets available?
There are three types of magnets: permanent magnets, temporary magnets, and electromagnets.
- Permanent magnets emit a magnetic field without the need for any external source of magnetism or electrical power.
- Temporary magnets behave as magnets while attached to or close to something that emits a magnetic field, but lose this characteristic when the source of the magnetic field is removed.
- Electro-magnets require electricity in order to behave as a magnet. top