A magnet is an object that is capable of creating a magnetic field. All magnets must have at least one North Pole, and one South Pole.
Most people are familiar with the basic traits of magnets, and know that they attract metal objects. Specifically, magnets attract objects made from iron, nickel, and cobalt. However magnets are used in many other ways due to the fact that they are able to affect electrically charged particles and electric conductors. Because of these properties, magnets are capable of converting electrical energy to mechanical energy and vice versa.
Some practical uses of this capability are found in thousands of different products that rely on magnets to operate, such as loudspeakers, generators, microphones, motors, eddy current and hysteresis torque devices, magnetic resonance equipment, sensors, gauges, switches, etc.
A magnetic field is an area of space where there is a detectable magnetic force. A magnetic force has a measurable strength and direction.
Magnetism refers to the force of attraction or repulsion that exists between substances made of specific materials such as iron, nickel, cobalt and steel. This force exists due to the motion of the electrical charges within the atomic structure of these materials.
A permanent magnet continues to emit magnetic force even without a power source, whereas an electromagnet requires power in order to generate a magnetic field.
A permanent magnet will retain its magnetism unless it is affected by a strong outside magnetic or electrical force, or elevated temperatures. If they are not exposed to any of these conditions, permanent magnets will still lose magnetism on their own, however this degradation is very slow, on the order of one percentage point every ten years or so.
Yes, if a magnet is influenced by another strong magnet, is affected by a powerful electrical force, or is exposed to temperatures above a certain level, it may lose some or all of its magnetic strength. Be sure to identify the properties of the magnet in question before using it if loss of strength is a concern.
Depending on how the magnet in question lost its strength, it may be able to be re-magnetized. Once a magnet is fully saturated, it cannot be made any stronger.
An isotropic magnet is not oriented during the manufacturing process, and can therefore be magnetized in any direction after it is made. In contrast, an anisotropic magnet is exposed to a strong magnetic field during the manufacturing process in order to orient the particles in a specific direction. As a result, anisotropic magnets can only be magnetized in one direction; however they generally have stronger magnetic properties.
If allowed to move freely, a magnet will align itself with the north-south polarity of the earth. The pole that seeks south is called the "south pole" and the pole that points north is called the "north pole."
The poles of a magnet are identical, so you cannot see or feel the difference between them. An easy way to check the poles of a magnet is to use a compass. The part of the needle that normally points north will seek the south pole of the magnet.
Magnets are made using the following methods:
- Pressing and Sintering
- Injection Molding
- Compression Bonding
Permanent magnets may be made from any for the following materials:
- Strontium-Iron (Ferrite or Ceramic)
- Neodymium-Iron-Boron (a Rare Earth magnet, Sintered or Bonded)
- Samarium Cobalt (a Rare Earth magnet)
- Aluminum-Nickel-Cobalt (Alnico)
When a magnet is incorporated into a housing or permanently mounted to another part, it may be called a magnetic assembly. The most common types of magnetic assemblies are those that are designed to increase the pull strength that the magnet would normally exhibit. Some magnetic assemblies, like round bases or channel assemblies, can be more than 30 times as strong as the magnet would be on its own.
Magnetic strength is measured in a few different ways. Here are a few examples:
- A Gauss Meter is used to measure the strength of the field a magnet emits in units called "gauss."
- Pull Testers can be used to measure the amount of weight a magnet can hold in pounds or kilograms.
- Permeameters are used to identify the exact magnetic characteristics of a specific material.