What is an electromagnet? Their types and purposes

The article describes what an electromagnet is, by what principle it is arranged, and in which spheres this type of magnets is used.

Magnetism

Probably one of the most surprising, but at the same time simple physical reactions is magnetism. More than three thousand years ago, many scientists of ancient Greece and China were aware of the unusual properties of "magnetic stones."

At the same time, magnets do not surprise anyone, even the most powerful ones - based on neodymium. They are often sold as trinkets or they can be found inside various devices and mechanisms. However, few know how important magnetism is for scientific and technological progress.

But at the beginning of the XIX century, such a device as an electromagnet was created. So what is an electromagnet, how it is arranged and where it is applied? We will talk about this in this article.

Definition

An electromagnet is a special device, the work of which 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 various thickness, necessarily covered with insulation. But there are also electromagnets from superconducting materials. The magnetic cores themselves are made of steel, iron-nickel alloys or cast iron. And in order to minimize losses on eddy currents, the magnetic cores are structurally executed from a whole set of thin sheets. Now we know what an electromagnet is. Let's take a closer look at the history of creating 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 was wound a thick insulated copper wire. At the time when an electric current was being pushed through it, the metal rod acquired the properties of a magnet. And when the current flow was interrupted, all the magnetism device immediately lost. It is this quality - the inclusion and deactivation, if necessary - and allows the use of electromagnets in a number of technological and industrial spheres.

We have considered the question of what an electromagnet is. Now let's analyze its main types. They are divided according to the method of creating the magnetic field. But their function remains the same.

Kinds

Electromagnets come in the following forms:

• Neutral direct current. In such a device, the magnetic flux is created by a constant electric current passed through the winding. So, the force of attraction of such an electromagnet varies depending only on the magnitude of the current, and not on its direction in the winding.
• Polarized direct current. The action of an electromagnet of this kind is based on the presence of two independent magnetic fluxes. Speaking about polarizing, its presence is usually created by permanent magnets (in rare cases - by additional electromagnets), and it is needed to create an attractive force with the winding turned off. And the action of such an electromagnet depends on the magnitude and direction of the electric current that moves in the winding.
• Alternating current. In such devices, the coil of the electromagnet 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, because of what it "pulsates" from the minimum to the maximum value with a frequency that has a double value with respect to the frequency of the electric current feeding it.

With what kinds of them are, we have already read. Now let us consider examples of the use of electromagnets.

Industry

Probably, all though time, but saw versions of such device, as electromagnet lifting. This is a thick "pancake" of various diameters, which has a huge force of attraction and is used to carry cargo, scrap metal and any other metal. Convenience is that it is enough to turn off the power - and the entire load immediately detaches, and vice versa. This greatly simplifies the loading and unloading process.

The strength of the electromagnet, 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 area of the working surface of the device.

Medicine

Even at the end of the XIX century, electromagnets were used in medicine. One such example is a special apparatus that could extract foreign bodies (metal shavings, rust, scale, etc.) from the eye.

And in our time, electromagnets are also widely used in medicine, and, probably, one of such devices, about which everyone has heard, is an MRI. It works on the basis of magnetic-nuclear resonance, and, in fact, is a huge and powerful electromagnet.

Equipment

Also, such 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 fast and easy to operate, but it is enough to de-energize the building in an emergency situation, and all of them will open, which is very convenient for a fire.

Well, of course, the work 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.