A Brief History Of Magnets
The ancient Greeks were the first to use a naturally occurring iron ore called magnetite. The first application was the mariner’s compass. Magnetite then became known as lode-stone, the word lode meaning to lead.
1600 Gilbert discovered the earth is one giant magnet.
1785 Charles Coulomb discovered the square law of attraction and repulsion between electrical charges and magnetic poles.
1820 Hans Oersted discovered that an electrical current would deflect magnetic needles.
1830 Michael Faraday discovered electromagnetic induction.
1865 The invention of the dynamo and the start of the era of electricity.
1873 James Maxwell published the discoveries of Gauss, Ampere and Faraday’s theories today known as Maxwell’s equations of the relationship of electricity and magnetism.
1921 Saw the introduction of Cobalt and Chrome steels.
1935 Aluminium, Nickel and Cobalt known as Alnico was developed.
1950 Philips produced the first non-metallic magnets know as Ferrites.
1970 Stronger Samarium Cobalt magnets, known as Rare Earth magnets, became available.
1983 The Japanese patented Neodymium Iron Boron magnets.
2000 Rapid advances within Neodymium magnets continues with ever increasing performance and corrosion resistance being developed.
There are many different magnet materials and grades to choose from. For help in choosing which is the best for your application, see our Application Guide.
Magnet materials generally fall into four main family groups. These are,
- Samarium Cobalt (SmCo)
- Neodymium-Iron-Boron (NdFeB)
This site contains the majority of our standard sizes, which are normally available from stock or at short notice. It is recommended you seek our advice when making your selection to ensure that you are always using the correct magnet for the job. If you do not see the size you require, please ask anyway since other sizes can often be supplied at short notice.
Health and Safety
Anyone handling magnets must be instructed about the following safety rules,
- Pacemakers and magnetically stored data will be affected or damaged by magnets.
- Beware that modern permanent magnets may attract steel or other magnets with high mechanical forces. Big magnets act over wide distances and can cause injuries.
- Most sintered magnets are hard and brittle. If such magnets snap together they may shatter into many parts with sharp edges. Always wear safety glasses when handling such magnets.
- Strong magnetic fields may influence or distort sensitive electronic or mechanical test instruments. Very sensitive devices may even be destroyed. Always keep magnets at a safe distance from such devices.
- Never handle magnets in an environment where explosive gas could be present. Moving or snapping of magnets, mainly those from rare-earth metals, may cause sparking.
- When machining or grinding magnets, the dust or chips may burn. The fine dust of rare-earth magnets is pyrophoric and oxidizes rapidly, causing high temperatures. Never grind such magnets without plenty of coolant, and take proper precautions for handling the grinding dust.
- Permanent magnets should not be exposed to strong radiation over long periods of time. Some magnetic properties may be influenced.
- Always watch for the maximum temperature to which a magnet may be exposed. Basically, high temperatures decrease the magnetic properties.
Neodymium magnets are extremely susceptible to corrosion. Great care should be taken to avoid Hydrogen or salt water environments. These magnets must also be stored in a dry environment in order to avoid oxidation of the surface.
Influence On Human Beings
No negative effects are known when touching magnets. Only very strong magnetic fields with flux densities of 1 Tesla or more and long-time exposure to such fields may cause biological changes. Many reports exist which, claim beneficial effects to low and medium flux-densities. Scientific opinions are controversial.
People allergic to ceramics or certain materials may react likewise when coming in contact with magnet material, whether magnetised or not. In special cases, please, ask for more details.
What is a permanent magnet?
A permanent magnet is any material that when exposed to a strong magnetic field will begin to exhibit a magnetic field of its own and continue to do so when the original field is removed. This exhibited magnetic field will be continuous without weakening provided that the material is not exposed to environment or external magnetic field changes. The ability to resist changes in its magnetic field is used to define the types of applications suitable for a permanent magnet. Generally speaking only special alloys have the capability to become permanent magnets.
Directions of Magnetism