The article describes what an electromagnet is, on what principle it is arranged, and in what areas this type of magnet is used.
Magnetism
Probably one of the most amazing yet simple physical reactions is magnetism. More than three thousand years ago, many scientists of ancient Greece and China knew the unusual properties of "magnetic stones".
In our time, you will not surprise anyone with magnets, even the most powerful ones - based on neodymium. They are often sold as trinkets or can be found inside various appliances and mechanisms. However, few people know how important magnetism is for scientific and technological progress.
But at the beginning of the 19th century, such a device as an electromagnet was created. So what is an electromagnet, how does it work and where is it used? We will talk about this in this article.
Definition
An electromagnet is a special device whose operation creates a magnetic field when an electric current is applied to it. Most often, electromagnets consist of a primary winding and a core that has ferromagnetic properties.
The winding is usually made of copper or aluminum wire of variousthickness, necessarily covered with insulation. But there are also electromagnets made of superconducting materials. The magnetic circuits themselves are made of steel, iron-nickel alloys or cast iron. And in order to minimize eddy current losses, magnetic cores are structurally made from a whole set of thin sheets. Now we know what an electromagnet is. Let's take a closer look at the history of this useful device.
History
The creator of the electromagnet is William Sturgeon. It was he who in 1825 made the first such magnet. Structurally, the device was a cylindrical piece of iron around which a thick insulated copper wire was wound. At the moment when an electric current was passed through it, the metal rod acquired the properties of a magnet. And when the current flow was interrupted, the device immediately lost all magnetism. It is this quality - switching on and off if necessary - that allows the use of electromagnets in a number of technological and industrial fields.
We have considered the question of what an electromagnet is. Now let's look at its main types. They are divided depending on the method of creating a magnetic field. But their function remains the same.
Views
Electromagnets are of the following types:
- Neutral DC. In such a device, the magnetic flux is created by means of a direct electric current passed through the winding. This means that the attractive force of such an electromagnet varies depending only on the magnitudecurrent, and not from its direction in the winding.
- Polarized DC. The action of an electromagnet of this kind is based on the presence of two independent magnetic fluxes. If we talk about polarizing, then its presence is usually created by permanent magnets (in rare cases, additional electromagnets), and it is needed to create an attractive force when the winding is off. And the action of such an electromagnet depends on the magnitude and direction of the electric current that moves in the winding.
- AC. In such devices, the electromagnet coil is powered by alternating current electricity. Accordingly, with a certain periodicity, the magnetic flux changes its direction and magnitude. And the force of attraction varies only in magnitude, which is why it "pulsates" from a minimum to a maximum value with a frequency that is twice the frequency of the electric current that feeds it.
We have already familiarized ourselves with what types of them are. Now consider examples of the use of electromagnets.
Industry
Probably everyone at least once, but saw a variety of such a device as a lifting electromagnet. This is a thick "pancake" of various diameters, which has a huge force of attraction and is used to carry cargo, scrap metal, and in general any other metal. Its convenience lies in the fact that it is enough to turn off the power - and the entire load is immediately unhooked, and vice versa. This greatly simplifies the process of loading and unloading.
Strengthelectromagnet, by the way, is calculated by the following formula: F=40550∙B^2∙S. Let's consider it in more detail. In this case, F is the force in kilograms (can also be measured in Newtons), B is the induction value, and S is the working surface area of the device.
Medicine
As early as the end of the 19th century, electromagnets were used in medicine. One such example is a special apparatus that could remove foreign bodies (metal chips, rust, scale, etc.) from the eye.
And in our time, electromagnets are also widely used in medicine, and probably one of these devices that everyone has heard of is MRI. It works on the basis of magnetic nuclear resonance, and, in fact, is a huge and powerful electromagnet.
Technique
Also, similar magnets are used in various techniques and electronics, and in the domestic sphere, for example, as locks. Such locks are convenient because they are very quick and easy to use, but at the same time it is enough to de-energize the building in an emergency - and all of them will open, which is very convenient in case of fire.
And, of course, the operation of all relays is based on the principles of electromagnetism.
As you can see, this is a very important device that has found application in various fields of science and technology.
