A electromagnet it’s a magnet artificial that presents a iron core with a coil around it, an electric current passing through said coil. The iron of the electromagnet is sweet iron: that is, without impurities.

Magnetic field

The magnetic field, in this case, it is generated through the flow of the current. If the current is interrupted, the magnetic field of the electromagnet disappears.

Electromagnet machine

A large industrial electromagnet in a landfill

Unlike what happens with permanent magnets, in electromagnets it is possible to modify the magnetic field quickly by acting on the electric current. It is important to note that maintaining the countryside it demands the constant use of a power supply.

It is attributed to the Danish Hans Christian Ørsted the discovery of the physical link that exists between electricity and the magnetism: that is, between electric flow and the magnetic fields. English William SturgeonMeanwhile, he was the one who created the first electromagnet in the mid-1990s. 1920.

Operation and applications

The operation of an electromagnet is based on the magnetic domains found at the core of iron. These domains behave like small magnets that, without the incidence of electric current, are distributed in different directions and cancel each other out. Upon receiving the current, the magnetic domains align and the magnetic field arises.

Electromagnets are used in multiple contexts where it is necessary to have a variable electromagnetic field. There are cranes; automobile clutches and brakes; switches; and engines that resort to electromagnets. The magnetic levitation trains, for their part, they also use electromagnets to levitate. As can be seen, not all electromagnets have the same attraction capacity in terms of maximum weight; a homemade one, for example, will only be able to hold light objects.

Electromagnet in a few steps

Despite what it may appear to read too much of a definition technique, building an electromagnet is something that we can all do at home using easily available elements. The materials we need are the following: a static battery; a copper wire of an extension that is not below the meter; an iron screw more than 10 centimeters long; Scotch tape.

To assemble the electromagnet we must start by carefully winding the cable around the screw, so that each turn is next to the previous one, as if we were reproducing the shape of the old telephone cables, but with higher density. In addition, we must do it with the greatest possible tension. It is important to leave a free section both at the beginning and at the end, as well as an initial and final margin of at least 1 centimeter in the screw.

Battery electromagnet

An ideal battery to make a homemade electromagnet

Once this step is finished, we will have to adjust the cable to the screw making use of the adhesive tape, to prevent it from coming loose. It is not necessary to cover everything, but simply the beginning and the end. Finally, we cling each end of the cable to one pole of the battery, for which we can fold it into small circles. And, voila, we already have an electromagnet, whose operation we can test by bringing it closer to any small metal object that we have within our reach, which will inevitably be seen attracted.

As a curious fact, we can mention that if we disconnect one of the ends of the battery and bring the same object closer, the attraction will last a short time, because the magnetic force of the electromagnet vanishes when interrupting the flow of electric current. Because of the so-called joule effect, according to which a portion of the energy that circulates through the cable is transformed into heat, little by little we will notice that its temperature increases; for this reason it is recommended to disconnect it when it reaches a too high level.