Magnet

Jai Ganesh · Yesterday 17:06:38

Magnet

Gist

A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets.

A magnet is any object that produces its own magnetic field that interacts with other magnetic fields. Magnets have two poles, a north pole and a south pole. The magnetic field is represented by field lines that start at a magnet's north pole and end at the south pole.

Summary

A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets.

A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic). These include the elements iron, nickel and cobalt and their alloys, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestone. Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of magnetism.

Ferromagnetic materials can be divided into magnetically "soft" materials like annealed iron, which can be magnetized but do not tend to stay magnetized, and magnetically "hard" materials, which do. Permanent magnets are made from "hard" ferromagnetic materials such as alnico and ferrite that are subjected to special processing in a strong magnetic field during manufacture to align their internal microcrystalline structure, making them very hard to demagnetize. To demagnetize a saturated magnet, a certain magnetic field must be applied, and this threshold depends on coercivity of the respective material. "Hard" materials have high coercivity, whereas "soft" materials have low coercivity. The overall strength of a magnet is measured by its magnetic moment or, alternatively, the total magnetic flux it produces. The local strength of magnetism in a material is measured by its magnetization.

An electromagnet is made from a coil of wire that acts as a magnet when an electric current passes through it but stops being a magnet when the current stops. Often, the coil is wrapped around a core of "soft" ferromagnetic material such as mild steel, which greatly enhances the magnetic field produced by the coil.

Details

A magnet is a special kind of metal which is made out of (Iron Nickel and Cobalt) When a magnet goes near a special kind of metal or another magnet, and the poles (sides) touching are opposite, it will pull, or attract the other object closer. If the two poles are the same, the magnet and the other object will push away, or repel, from each other. This attraction and repulsion is called magnetism. All magnets have north and south poles. Opposite poles are attracted to each other, while the same poles repel each other like south and south and north and north. When you rub a piece of iron along a magnet, the north-seeking poles of the atoms in the iron line up in the same direction. The force generated by the aligned atoms creates a magnetic field.

Types of magnet

Soft magnets (meaning impermanent magnets) are often used in electromagnets some of the magnets are (bar magnet,wand and ball magnet). These increase (often hundreds or thousands of times) the magnetic field of a wire that carries an electrical current and is wrapped around the magnet. The field also increases with the current. Magnetic Materials: Soft Magnets. Soft magnetic materials are those materials that are easily magnetised and demagnetised.

Permanent magnets have ferromagnetism. They occur naturally in some rocks, particularly lodestone, but are now commonly manufactured. A magnet's magnetism decreases when it is heated and increases when it is cooled. It has to be heated at around 1,000 degrees Celsius (1,830 °F). Like poles (S-pole and S-pole/N-pole and N-pole) will repel each other while unlike poles (N-pole and S-pole) will attract each other.

Magnets are only attracted to special metals. Iron, cobalt and nickel are magnetic. Metals that have iron in them attract magnets well. Steel is one. Metals like brass, copper, zinc and aluminium, silver are not attracted to magnets. Non-magnetic materials such as wood and glass are not attracted to magnets as they do not have magnetic materials in them.

Rare earth magnets

Lanthanum elements can make strong magnets. The spin of their electrons can be aligned, resulting in very strong magnetic fields. So these elements are used for high-strength magnets when their high price is not a concern. The most common types of rare-earth magnets are samarium–cobalt and neodymium–iron–boron (NIB) magnets.

Natural magnets

Natural/permanent magnets are not artificial. They are a kind of rock called lodestone or magnetite.

The compass

A compass uses the Earth's magnetic field, and points to the North magnetic pole. A north side of the magnet is attracted to the south side of another magnet. However, the north side of the compass points to the north pole, this can only mean that the "north pole" is really the magnetic south, and the "South magnetic pole" is really the magnetic north.

Discovery

Ancient people discovered magnetism from lodestones (or magnetite) which are naturally magnetized pieces of iron ore. Lodestones, suspended so they could turn, were the first magnetic compasses.

The earliest known surviving descriptions of magnets and their properties are from Anatolia, India, and China about 2500 years ago. The properties of lodestones and their affinity for iron were written of by Pliny the Elder in his encyclopedia Naturalis Historia.

Additional Information

A magnet is any material capable of attracting iron and producing a magnetic field outside itself. By the end of the 19th century all the known elements and many compounds had been tested for magnetism, and all were found to have some magnetic property. The most common was the property of diamagnetism, the name given to materials exhibiting a weak repulsion by both poles of a magnet. Some materials, such as chromium, showed paramagnetism, being capable of weak induced magnetization when brought near a magnet. This magnetization disappears when the magnet is removed. Only three elements, iron, nickel, and cobalt, showed the property of ferromagnetism (i.e., the capability of remaining permanently magnetized).

You probably know that magnets attract specific metals and they have north and south poles. Opposite poles attract each other while like poles repel each other. Magnetic and electrical fields are related, and magnetism, along with gravity and strong and weak atomic forces, is one of the four fundamental forces in the universe.

But none of those facts answers the most basic question: What exactly makes a magnet stick to certain metals? Or why don't they stick to other metals? Why do they attract or repel each other, depending on their positioning? And what makes neodymium magnets so much stronger than the ceramic magnets we played with as children?

To understand the answers to these questions, it helps to have a basic definition of a magnet. Magnets are objects that produce magnetic fields and attract metals like iron, nickel and cobalt. The magnetic field's lines of force exit the magnet from its north pole and enter its south pole. Permanent or hard magnets create their own magnetic field all the time. Temporary or soft magnets produce magnetic fields while in the presence of a magnetic field and for a short while after exiting the field. Electromagnets produce magnetic fields only when electricity travels through their wire coils.

Because electrons and protons are tiny magnets, all materials have some sort of magnetic property. In most materials, however, the way electrons spin in opposite directions cancels out an atom's magnetic properties. Metals are the most common choices to manufacture magnets. Although some are made from simple metals, combinations of metals — called alloys — produce magnets of different strengths. For example:

Ferrites or ceramic magnets: These are like those used in refrigerator magnets and elementary-school science experiments. They contain iron oxide and other metals in a ceramic composite. A ceramic magnet known as lodestone, or magnetite, was the first magnetic material discovered and occurs naturally. Even though the ceramic magnet has been around for so long, they weren't commercially produced until 1952. Although they're common and keep their magnetism, they tend to have a weaker magnetic field (known as the energy product) than other types of magnets.

Alnico magnets: These were developed in the 1930s and are made from aluminum, nickel and cobalt. They're stronger than ceramic magnets, but not as strong as the ones that incorporate a class of elements known as rare-earth metals.

Neodymium magnets: These contain iron, boron and the rare-earth element neodymium, and as of this writing, they are the strongest commercially available magnets. They first appeared in the 1980s after scientists at the General Motors Research Laboratories and the Sumitomo Special Metals Company published their research.

Samarium cobalt magnets: These were developed by scientists at the Dayton University Research University in the 1960s, and combine cobalt with the rare-earth element samarium. In the past few years, scientists have also discovered magnetic polymers, or plastic magnets. Some of these are flexible and moldable. However, some work only at extremely low temperatures, and others pick up only very lightweight materials, like iron filings.

The Basics

Many of today's electronic devices require magnets to function. This reliance on magnets is relatively recent, primarily because most modern devices require magnets that are stronger than the ones found in nature. Lodestone, a form of magnetite, is the strongest naturally occurring magnet. It can attract small objects, like paper clips and staples.

By the 12th century, people had discovered that they could use lodestone to magnetize pieces of iron, creating a compass. Repeatedly rubbing lodestone along an iron needle in one direction magnetized the needle. It would then align itself in a north-south direction when suspended. Eventually, scientist William Gilbert explained that this north-south alignment of magnetized needles was due to Earth behaving like an enormous magnet with north and south poles.

A compass needle isn't nearly as strong as many of the permanent magnets used today. But the physical process that magnetizes compass needles and chunks of neodymium alloy is essentially the same. It relies on microscopic regions known as magnetic domains, which are part of the physical structure of ferromagnetic materials, like iron, cobalt and nickel. Each domain is essentially a tiny, self-contained magnet with a north and south pole. In an unmagnetized ferromagnetic material, each domain's north pole points in a random direction. Magnetic domains that are oriented in opposite directions cancel one another out, so the material does not produce a net magnetic field.

In magnets, on the other hand, most or all the magnetic domains point in the same direction. Rather than canceling one another out, the microscopic magnetic fields combine to create one large magnetic field. The more domains point in the same direction, the stronger the overall field. Each domain's magnetic field extends from its north pole into the south pole of the domain ahead of it.

This explains why breaking a magnet in half creates two smaller magnets with north and south poles. It also explains why opposite poles attract — the field lines leave the north pole of one magnet and naturally enter the south pole of another, essentially creating one larger magnet. Like poles repel each other because their lines of force are traveling in opposite directions, clashing with each other rather than moving together.

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#1 Yesterday 17:06:38

Magnet

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