The article talks about what an electromagnet is, by what principle it is designed, and in what areas this type of magnets is used.
Magnetism
Probably one of the most amazing, but at the same time simple physical reactions is magnetism. More than three thousand years ago, many scholars of ancient Greece and China were aware of the unusual properties of "magnetic stones."
In our time, magnets will not surprise anyone, even the most powerful ones based on neodymium. They are often sold as trinkets or you can meet them inside various devices and mechanisms. However, few people know how important magnetism is to scientific and technological progress.
But at the beginning of the 19th century, a device such as an electromagnet was created. So what is an electromagnet, how is it designed, 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, which has ferromagnetic properties.
The winding is usually made of copper or aluminum wire of various thicknesses, necessarily coated with insulation. But there are electromagnets from superconducting materials. Magnetic cores themselves are made of steel, iron-nickel alloys or cast iron. And in order to minimize eddy current losses , magnetic circuits are structurally made from a whole set of thin sheets. Now we know what an electromagnet is. Consider in more detail the history of the creation 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 electric current was launched through it, a rod of metal 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 examined the question of what an electromagnet is. Now let's analyze its main types. They are divided depending on the method of creating a magnetic field. But their function remains the same.
Kinds
Electromagnets are of the following types:
- Neutral DC. In such a device, a magnetic flux is generated by direct current flowing through a winding. So, the attractive force of such an electromagnet varies depending only on the magnitude of the current, and not on 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, by additional electromagnets), and it is needed to create 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.
- Alternating current. In such devices, the electromagnet coil is powered by AC 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 which it “pulsates” from minimum to maximum value with a frequency that has a double value in relation to the frequency of the electric current that feeds it.
With what their types are, we have already become familiar. Now consider the use of electromagnets.
Industry
Probably, at least once, but they saw varieties of such a device as a lifting electromagnet. This is a thick “pancake” of various diameters, which has tremendous gravity and is used to carry cargo, scrap metal and any other metal in general. Its convenience lies in the fact that it is enough to turn off the power - and the whole load is immediately disconnected, and vice versa. This greatly simplifies the process of loading and unloading.
The strength of an 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 working surface area of the device.
The medicine
At the end of the XIX century, electromagnets were used in medicine. One of such examples is a special apparatus that could remove foreign bodies from the eye (metal shavings, rust, scale and others).
And in our time, electromagnets are also widely used in medicine, and, probably, one of such devices that everyone heard about is MRI. It works on the basis of nuclear magnetic resonance, and, in fact, is a huge and powerful electromagnet.
Equipment
Also, such magnets are used in various equipment and electronics, and in the household sphere, for example, as locks. Such locks are convenient in that they are very quick and easy to operate, but at the same time it is enough to disconnect the building from power in an emergency - and they will all open, which is very convenient in case of fire.
Well, 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.