An electromagnet is a type of magnet in which the magnetic field is produced by the flow of an electric current. If the flow of electric current disappears, the magnetic field and its resulting effect also disappear.
There are different types of electromagnets depending on the direction of the current and the desired power. Among them we highlight those of circular current, direct current, rectangular and those of drive.
How Does an Electromagnet Work?
An electromagnet works thanks to the property that all electrical conductors experience: when a current flows through a conductor, a magnetic field is always generated.
The simplest electromagnet is a piece of metal wire wound into a coil. A cylindrical coil with the wire wound in a helix shape (similar to a corkscrew in the shape of a corkscrew) is often called a solenoid; a closed solenoid would be a torus. The ends of the cable are connected to a power source.
Stronger magnetic fields can be produced if a core of a paramagnetic or ferromagnetic material is placed inside the coil, usually a soft iron core is used. The core concentrates the magnetic field so that it will be stronger than if there were only the coil winding.
An electromagnet can work with both alternating current and direct current.
The magnetic fields originated by the coils follow a form of the right hand rule. If the fingers of the left hand are bent in the direction of the flow of the electron current through the coil, the thumb points in the direction of the magnetic force.
The side of the magnet from which the field lines arise is considered the North Pole.
Who Invented the Electromagnet?
The inventor of the electromagnet was the English physicist William Sturgeon , in 1825.
The first electromagnet was a horseshoe-shaped piece of iron surrounded by a coil. In this horseshoe, when the current passed through the coil of the electromagnet it became magnetized and when it stopped it was demagnetized.
Sturgeon demonstrated the magnetic properties of the electromagnet by lifting about 4 kg with a piece of iron weighing less than 200 grams with a coil through which the current of a single cell battery passed.
In addition, Sturgeon could regulate his electromagnet by varying the intensity of the electric current.
Examples of Use of Electromagnets
These elements can be used directly or indirectly. In both cases we can find the following examples:
To deflect electrically charged particles, as in cathode ray tubes, or particle accelerators.
To lift large masses of iron. Some cranes use powerful industrial electromagnet to hook and lift scrap iron.
Electric motors. Electric motors work using this technology.
Electric generators. It works in the same way as in electric motors but in reverse.
Closure of electrical contacts on relays or operate valves on solenoid valves.
Activate electric locks
Moving the head of a hard drive
Electromagnetic brakes and clutches for automobiles.
To magnetically separate metals in recycling centers.
Maglev trains use this technology to float and greatly reduce friction losses with the track.
Example of Use in Automatic Doors
Another example of use is in the field of locks, where it is used to keep a door closed, ensuring its opening in the event of a power outage.
Around 1980, the magnetic field derived from an electromagnet began to be used in construction and, more precisely, in the field of security windows.
A Swiss company began to produce an electromagnet, of very small size and weight, which, when supplied at low voltage (12Vdc - 24 Vdc), developed a magnetic field capable of withstanding a force of several thousand newtons.
This application was immediately a great success in the field of emergency exits because it guarantees security against theft without the need to use mechanical parts but, at the same time, it ensured the opening of the door, without human intervention, in case of power failure. .
The evolution of this system has led the construction sector to massively use the electromagnet as an electrical closing element. Today it is used in various ways depending on the dimensions, uses, profiles and type of door.
What Are the Differences Between a Magnet and an Electromagnet?
The most important differences between a permanent magnet and an electromagnet are the following:
The magnetic field of an electromagnet can be manipulated quickly by controlling the amount of electrical current. On the contrary, it is necessary that there be a continuous supply of electrical energy to maintain the field.
The magnetic force of the electromagnet depends on the electrical supply. If the current stops flowing, the electromagnet loses its properties.