Magnet and magnetic field: why is only metal attracted? .

Sometimes it happens that it is necessary to determine what metal or alloy a coin is made of. The first thing that comes to mind is to pay attention to its color. But then it turns out that, for example, a yellow coin can be made of copper, brass, nickel-copper alloy, or other material. How then? A common testing method is to use a magnet. But for this you need to know whether copper is magnetic or not.

Copper is not magnetic

Scientific point of view

To determine which metals are not magnetic, you need to find out how all metals in general can relate to magnets and a magnetic field. With respect to the applied magnetic field, all substances are divided into diamagnetic, paramagnetic and ferromagnetic.

Each atom consists of a positively charged nucleus and negatively charged electrons. They move continuously, which creates a magnetic field. The magnetic fields of electrons in one atom can enhance or cancel each other, depending on the direction of their movement. Moreover, the following can be compensated:

• Magnetic moments caused by the movement of electrons relative to the nucleus are orbital.
• Magnetic moments caused by the rotation of electrons around their axis are spin moments.

If all magnetic moments are equal to zero, the substance is classified as diamagnetic. If only spin moments are compensated - to paramagnets. If the fields are not compensated, use ferromagnets.

How to identify stainless steel

The main property of stainless steel is chemical inertness, and not magnetism. If you follow the logic, then such a test should be a priority in determining the alloy.

The simplest tests to detect fakes:

• A drop of copper sulfate. The algorithm is based on the fact that iron is more active than copper and displaces it. Thus Fe+CuSO₄ = FeSO₄+Cu. Copper will settle on the surface in the form of a reddish coating.
• Sodium chloride. A concentrated solution of table salt can bring to clean water an alloy that is not resistant to alkalis.

Physical methods:

• The thermal conductivity of alloy steel is lower than that of carbon steel. Therefore, the water in such a container heats up more slowly.
• The density corresponds to the declared one. Archimedes' law on displaced liquids is surrounded by parables: the crown displaced a smaller volume of water than the ingot that was used to make it. Therefore, the master diluted the gold with copper.

By sparks:

• When welding, carbides burn out, but in stainless steel there are fewer of them. Sanding with an angle grinder should reveal light white sparkles.

Such methods will help determine whether the product is actually made of stainless steel, but do not determine food grade steel or grade. For example, AISI 204 looks like AISI 304, but is not a full-fledged analogue. It cannot be used to make structures used in marine climates. For the production of chimneys, heat-resistant alloys are used, since they are simultaneously exposed to temperature and combustion products, which are acidic in nature.

Even if the product is made of stainless steel, its service life may be significantly reduced. The best possible option: choose trusted manufacturers, purchase products that have quality certificates.

Paramagnets and ferromagnets

Let's consider the option when each atom of a substance has its own magnetic field. These fields are multidirectional and compensate each other. If you place a magnet next to such a substance, the fields will be oriented in one direction. The substance will have a magnetic field, a positive and a negative pole. Then the substance will be attracted to the magnet and can itself become magnetized, that is, it will attract other metal objects. For example, you can magnetize steel clips at home. Each one will have a negative and a positive pole, and you can even hang a whole chain of paper clips on a magnet. Such substances are called paramagnetic.

Ferromagnets are a small group of substances that are attracted to magnets and are easily magnetized even in a weak field.

Diamagnets

In diamagnetic materials, the magnetic fields inside each atom are compensated. In this case, when a substance is introduced into a magnetic field, the movement of electrons under the influence of the field will be added to the natural movement of electrons. This movement of electrons will cause an additional current, the magnetic field of which will be directed against the external field. Therefore, the diamagnetic material will be weakly repelled from the nearby magnet.

So, if we approach the question from a scientific point of view, which metals are not magnetic, the answer will be – diamagnetic.

Distribution of paramagnets and diamagnets in the periodic table of Mendeleev elements

The magnetic properties of simple substances change periodically with increasing atomic number of the element.

Substances that are not attracted to magnets (diamagnets) are located mainly in short periods - 1, 2, 3. Which metals are not magnetic? These are lithium and beryllium, and sodium, magnesium and aluminum are already classified as paramagnetic.

Substances that are attracted to magnets (paramagnets) are located mainly in the long periods of the Mendeleev periodic system - 4, 5, 6, 7.

However, the last 8 elements in each long period are also diamagnetic.

In addition, three elements are distinguished - carbon, oxygen and tin, the magnetic properties of which are different for different allotropic modifications.

In addition, there are 25 more chemical elements whose magnetic properties could not be established due to their radioactivity and rapid decay or the complexity of synthesis.

The magnetic properties of lanthanides and actinides (all of which are metals) change irregularly. Among them there are para- and diamagnetic materials.

There are special magnetically ordered substances - chromium, manganese, iron, cobalt, nickel, the properties of which change irregularly.

Magnetic properties of metals table – ooo-asteko.ru

The reference tables give the specific magnetic susceptibility χ of some para- and diamagnetic bodies, which for isotropic bodies is determined by the expression:

χ = Y/H

where Y denotes the magnetization 1g of the body, and H is the strength of the external magnetizing field.

Table of magnetic susceptibility χ for elements

Solids are assumed to be in an isotropic state. Temperatures (t °C) correspond to the centigrade scale.

Table of magnetic susceptibility χ for some compounds, organic and inorganic

Solids are assumed to be in an isotropic state. Temperatures (t °C) correspond to the centigrade scale.

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Source of information: BRIEF PHYSICAL AND TECHNICAL GUIDE / Volume 1, - M.: 1960.

NON-MAGNETIC MATERIALS

NON-MAGNETIC MATERIALS, materials with low magnetic permeability ($μ⩽1.5$). There are dia- and paramagnetic, weakly ferromagnetic and antiferromagnetic materials.

Strictly speaking, there are no materials that do not have magnetic properties at all, because...

Diamagnetism is a property inherent in all substances, which, to a greater or lesser extent, can be overlapped by electronic or nuclear paramagnetism, ferromagnetism or antiferromagnetism.

Nonmetallic materials include most metals and alloys (including austenitic steels and cast irons), as well as most polymers and composites based on them, wood, glass, and many other materials. As structural materials, they are most widely used due to their high mechanical properties.

properties, wear resistance and durability, received metallic. N. m., ch. arr. non-magnetic steels and cast irons, as well as alloys of copper, aluminum, titanium (for example, titanium nickelide), etc.

The nonmagnetic nature of steels and cast irons is ensured by the creation of an austenite structure in them, which is achieved by appropriate alloying. Non-magnetic steel and cast iron are characterized by high electrical resistivity. The best technological

properties are possessed by chromium-nickel non-magnetic steels, produced in the form of sheets, wire and strips. Typical composition of non-magnetic steel: up to 0.12% (by weight) $ce{C}$, up to 0.8% $ce{Si}$, 1–2% $ce{Mn}$, 17–19% $ce {Cr}$, 11–13% $ce{Ni}$, the rest $ce{Fe};; μ$= 1.05–1.2.

For parts with complex configurations that do not require high strength, cheaper non-magnetic cast irons are used, the specific electric whose resistance (1.4–2.0 μΩ m) is generally greater than that of non-magnetic steels (approx.

1 µOhm m), which ensures low energy losses due to eddy currents in parts operating on alternating current. The most common nickel-manganese cast irons contain (in addition to $ce{Fe}$) 2.6–3.2% $ce{C}$, 5–7.5% $ce{Mn}$, 9–12% $ ce{Ni}$, 2.5–3.5% $ce{Si}$ and up to 1.1% $ce{P};; μ$=1.03–1.06. N. m.

based on non-ferrous metals, they usually have a lower magnetic permeability than non-magnetic steels and cast irons, they are well processed by cutting and pressure, but their mechanical properties. properties are not always satisfactory, and electrical. little resistance.

N.M. is used for the manufacture of parts that should not have a magnetic effect on the working measuring system. installations, instruments, machines and apparatus. From N. m.

Compass boxes are being prepared and parts will be measured electrically.

instruments and clocks, non-magnetic springs, bushings and flanges (through which AC cables pass), tightening bolts and casings of transformers and electrical machines, special. (non-magnetic) honey. equipment, etc.

What metals are not magnetic: list

There are only 9 ferromagnets, that is, metals that are highly magnetic, in nature. These are iron, cobalt, nickel, their alloys and compounds, as well as six lanthanide metals: gadolinium, terbium, dysprosium, holmium, erbium and thulium.

Metals that are attracted only to very strong magnets (paramagnetic): aluminum, copper, platinum, uranium.

Since in everyday life there are no such large magnets that would attract a paramagnetic material, and also no lanthanide metals are found, we can safely say that all metals except iron, cobalt, nickel and their alloys will not be attracted to magnets.

So, what metals are not magnetic to a magnet:

• paramagnetic materials: aluminum, platinum, chromium, magnesium, tungsten;
• diamagnetic materials: copper, gold, silver, zinc, mercury, cadmium, zirconium.

In general, we can say that ferrous metals are attracted to a magnet, non-ferrous metals are not.

If we talk about alloys, then iron alloys are magnetic. These primarily include steel and cast iron. Precious coins can also be attracted to a magnet, since they are not made of pure non-ferrous metal, but of an alloy that may contain a small amount of ferromagnetic material. But jewelry made of pure non-ferrous metal will not be attracted to a magnet.

What is anti-corrosion steel?

Steel that does not become rusty during use is popularly called stainless steel. It is obtained from an alloy of iron with carbon and various alloying additives: nickel, chromium, niobium, titanium. Each of these components enhances or reduces certain properties of the alloy - magnetism, strength, hardness, ductility, corrosion. The main quality of stainless steel is corrosion resistance. It just depends on the chromium content in it.

The more of this metal in the alloy, the less susceptible it is to corrosion. Therefore, all steels that are resistant to rust contain at least 10.5% chromium. The uniqueness of this metal is that when it reacts with oxygen, it creates an oxide film on the surface of the product, which prevents the alloy from reacting with aggressive environments. Moreover, if the surface is damaged, the film forms again after the oxidation of chromium with oxygen.

Alkali metals are the MOST DANGEROUS and Active Elements! (December 2019).

Magnets are materials that create magnetic fields that attract certain metals. Every magnet has a north and south pole. Reverse poles attract while poles repel.

While most magnets are made from metals and metal alloys, scientists have developed ways to create magnets from composite materials such as magnetic polymers.

What creates magnetism?

Magnetism in metals is created by the uneven distribution of electrons in the atoms of certain metallic elements.

The uneven rotation and motion caused by this uneven distribution of electrons shifts the charge within the atom back and forth, creating magnetic dipoles.

When magnetic dipoles align, they create a magnetic domain, a localized magnetic region with north and south poles.

In non-magnetic materials, magnetic domains collide in different directions, canceling each other out. Whereas in magnetized materials, most of these domains are aligned, pointing in the same direction, which creates a magnetic field. The more areas that line up with each other, the stronger the magnetic force.

Magnet types:

• Permanent magnets (also known as hard magnets) are those that constantly produce a magnetic field. This magnetic field is caused by ferromagnetism and is the strongest form of magnetism.
• Temporary magnets (also known as soft magnets) are only magnetic in the presence of a magnetic field.
• Electromagnets require electric current to pass through their coil wires to create a magnetic field.

Development of magnets:

Greek, Indian and Chinese writers documented basic knowledge of magnetism more than 2,000 years ago. Much of this understanding was based on observations of the effects of magnesium (the naturally occurring magnetic mineral of iron) on iron.

Early research into magnetism dates back to the 16th century, but the development of modern high-strength magnets did not occur until the 20th century.

Before 1940, permanent magnets were used only in basic applications such as compasses and electrical generators called magnetos. The development of aluminum and nickel-cobalt (Alnico) magnets has allowed permanent magnets to replace electromagnets in motors, generators and loudspeakers.

The development of samarium-cobalt (SmCo) magnets in the 1970s created magnets with twice the magnetic energy density of any previously available magnet. Smaller, more powerful magnets contributed to the development of many electronic devices as we know them.

By the early 1980s, further research into the magnetic properties of rare earth elements led to the discovery of neodymium-iron-boron (NdFeB) magnets. NdFeB magnets again led to a doubling of magnetic energy over SmCo magnets.

Rare earth magnets are now used in everything from wristwatches and iPads to hybrid car engines and wind turbines.

Magnetism and temperature:

Metals and other materials have different magnetic phases, depending on the temperature of the environment in which they are located. As a result, a metal can exhibit more than one form of magnetism.

Iron, for example, loses its magnetism, becoming paramagnetic when heated above 1418 °F (770 °C).

The temperature at which a metal loses its magnetic force is called its Curie temperature.

Iron, cobalt and nickel are the only elements that, in metallic form, have Curie temperatures above room temperature. Thus, all magnetic materials must contain one of these elements.

Common ferromagnetic metals and their curie temperatures:

Sources: How Stuff Works, Inc. How do magnets work? //science. How it works. com/magnet1. HTM Wikipedia. Curie temperature. // ru. Wikipedia. org/wiki/Curie_temperature

Search magnet for gold and silver and its properties

Typically, powerful magnets are designed to find precious metals. A search magnet reacts to gold and silver quite strongly, and although it is difficult to find them in their pure form, its power is enough to pick up jewelry and coins from the ground. The main goal of all search engines is treasures, expensive coins, and sometimes just ferrous metal.

The article will describe the structure of the magnet and the basic principle of operation. He will also figure out what exactly can be found with its help and how to find expensive alloys. It will be explained in detail what ferromagnets, paramagnets and diamagnetic materials are. In addition, valuable tips and recommendations will be given that will greatly simplify the search for valuable items.

Does a magnet attract gold and silver?

Is it possible to find pure gold or silver with powerful magnets? No, since such metals are diamagnetic, that is, they are not attracted to magnets. But it's not all bad, thanks to all the power of neodymium alloy, it is possible to get some jewelry. Such objects usually have a ligature in them.

This alloy helps precious metals such as gold or silver acquire certain properties. For example, silver jewelry does not darken as much, but gold jewelry is more durable. But the most important thing is that the ligature allows magnetization and makes it possible to find various alloys.

But it is also possible to find pure gold or silver. At the beginning of the article it was said that iron boxes can be found. Typically, jewelry made of gold or silver is stored in such cases. So, walking through an attic or similar places, you can get rich, in the literal sense of the word.

Magnetic properties of various metals

In order to go hunting for valuable metals, you need to know what exactly will be attracted to a magnet. Since metals have different magnetic properties, and some do not have them at all. They can be divided into three groups:

Ferromagnets are metals with some of the best magnetic properties. Such metals are highly magnetic. These include ferrous metal.

Paramagnetic materials have the usual properties; they are readily attracted to a magnet, but do not have the function of magnetization. These include some alloys of jewelry and several types of non-ferrous metals.

And finally, diamagnetic materials. Such alloys are extremely difficult to respond to magnetic fields and greatly complicate the search for truly precious things. Diamagnets include gold, silver, aluminum, patina and other metals that even the strongest magnet does not pick up.

Is it possible to find gold with a magnet?

As already discussed earlier, jewelry and coins with gold can be lifted, but it is very problematic.

It is impossible to get pure gold with a magnet.

But if various factors are favorable, such as an iron box or paramagnetic jewelry lying nearby, then there is a chance to find it. Basically, only jewelry containing gold, such as bracelets, earrings and rings, can be caught with a magnet. The best places to search are sandy beaches, wells, and the sea or river bottom where a large number of people swim.

Use of chromium-nickel steel

Anti-corrosion steel 12Х18Н10Т is an environmentally friendly and durable material. The composition of the chromium-nickel alloy, in addition to the main component - iron, includes up to 19% chromium, which provides it with strong anti-corrosion properties, and 11% nickel, which transfers it to the class of austenites and imparts flexibility, strength and heat resistance. Due to its characteristics, it is widely used. Many people are interested in whether steel grade 12Х18Н10Т is magnetic or not? It is non-magnetic, like all austenitic alloys, and is used in the following industries:

• Chemical - aggressive acids: acetic, nitric, phosphoric are transported through pipes made of this grade of steel.
• Food – dairy, meat, alcohol.
• Mechanical engineering – production of parts in contact with acids and alkalis, production of welded equipment, exhaust system manifolds.
• Petroleum - for the manufacture of pipes.

In addition, chromium-nickel alloys are used in the fuel and energy sector. Furnace fittings and heat exchangers are made from them.