Permeability (electromagnetism)
Permeability in electromagnetism is a measure of how well a material can support the formation of a magnetic field. Materials with high permeability, such as iron and nickel, easily allow magnetic fields to form, making them essential in various applications like transformers and electric motors. In contrast, materials with low permeability, such as wood and plastic, do not have significant internal magnetic fields and thus do not interact effectively with external magnets.
The concept of permeability is crucial in understanding magnetic circuits, which rely on the flow of magnetic flux to perform specific functions. Permeability is denoted by the Greek symbol "mu" (µ) and is often compared with the magnetic constant of free space (µ0) in theoretical contexts. Scientists also distinguish between permeability and magnetic susceptibility, the latter measuring how different materials respond to magnetic fields.
In modern research, scientists are exploring innovative applications of magnetic permeability, particularly in data storage and security. New methods could enhance the durability and tamper-resistance of devices like credit cards and computer memory by manipulating the magnetic properties of materials, offering promising advancements in technology.
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Permeability (electromagnetism)
Permeability in electromagnetism refers to the degree to which a material supports the formation of a magnetic field. A material with a high permeability will more easily allow a magnetic field to form and vice versa. Permeability becomes a factor in the creation and use of magnetic circuits, which rely on the flow of a magnetic field to trigger a specific action. Magnetic circuits are used in a wide variety of devices, including transformers, switches, and electric motors.
Background
A magnet is a natural or manmade object that attracts other objects made of certain materials. These materials include iron or iron-derived products like steel and cobalt or nickel. Ancient people originally called natural magnets lodestones because they noticed that the stones attracted nails and other metallic objects.
Magnets have two poles, generally referred to as north and south. A magnet will attract objects made of elements such as iron and nickel; it will also attract another magnet if they are lined up so that opposite poles are near each other (north/south). However, when like poles are placed together (north/north or south/south) the magnets will repel each other.
The field that runs from one pole to the other is called a magnetic dipole. In contemporary times, methods have been devised to make electromagnets. These are made by taking a metal form and wrapping it with wire. Electricity is then run through the wire, generating a magnetic field that is adjustable in intensity. It is also possible to reverse the polarity of the magnetic field generated by an electromagnet, which makes them more useful than non-electromagnets for applications that involve magnetic circuits.
Several factors determine how well a magnetic circuit functions, including the reluctance of the magnetic field and the permeability of the material through which the field is passing. The reluctance refers to how easily the magnetic flux, or the amount of magnetism contained in the circuit, can pass through. Permeability refers to how easily the material allows the magnetic flux to form.
Overview
Objects made of certain materials are attracted to magnets because they have an internal field that is conducive to the magnetic field the magnet generates. The field in the magnet induces the other object to generate its own field, which then interacts with the force of the magnet to draw the two together. In some elements, this internal field is strong. This is the case with iron, nickel, and some other elements, which are easily attracted to magnets. They are often called ferrous materials. Other elements—including wood, air, and plastic—have little or no internal field and are not attracted to magnets.
This tendency to generate an internal field in response to the presence of a magnet is known as permeability. It is calculated by determining the relationship between the magnetic flux density and the strength of the magnetic field. The magnetic flux is the concentration of magnetic field lines that are contained within the area in question. In a permanent magnet, the field strength is determined largely by the type of material from which it is made. In an electromagnet, the amount of electric current used determines the magnet's strength.
The permeability of an element is reported by using the Greek symbol (, which is written as mu in English. Permeability does not have a unit of measurement attached to it; instead, it is more like a rating. For instance, elements with virtually no internal magnetic field—and therefore very low permeability—have a mu of 1. Air, wood, and plastic are all ranked 1 in permeability. Scientists are also interested in magnetic susceptibility, which measures the differences between the permeability of different elements.
Another important quantification of magnetic permeability is permeability in free space, or in a vacuum. This is known as the magnetic constant of the vacuum. Together with the speed of light and the permittivity of an electric current—the electrical equivalent of permeability—magnetic permeability is one of the three constants used to determine electric and magnetic fields. This concept assumes the location of an area of perfect free space, a vacuum with no stray rays of magnetism or other substances that would affect a magnetic field in any way. Theoretically, the permeability of an element would be different in this area because there would be no outside influences. Magnetic permeability in a vacuum is assumed to have a constant value of mu 0, and electric permittivity derives its value from a formula known as Coulomb's constant that incorporates the magnetic permeability.
In the twenty-first century, scientists are developing new ways to take advantage of the magnetic permeability of certain substances. One potential new use would affect the way information is encoded on credit cards and items that need to store and secure data. The technology could help protect data and make it possible to send information in situations that had previously presented problems.
Magnetic technology has been used for a number of years to encode memory on computers and on credit cards and other identifying documents. However, because it is put in place with a magnet, it can also easily be erased by exposing it to another magnet. This deletes the data and renders the device useless. Scientists are working on new ways to encode data by altering the permeability of the material used for the encoding. A magnet could then be used to read the data without altering it. This new technique of manipulating magnetic permeability could result in identification and credit cards that are more resistant to tampering. It could also provide new ways for computers to store and access data even when exposed to extreme conditions, such as those found in outer space.
Bibliography
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