La electromagnetic force or also known Electromagnetism is responsible for most of the interactions we see in our current environment, electricity is also capable of producing a magnetic field. Learn more about this topic here!
Electromagnetism
Electromagnetism is a process in which an attractive field is created by putting the current in the conduit, when a conductor has an electrical charge, it generates magnetic lines of force from the conductor.
For example, if the current, i.e. positive charges moving in a wire, produces the magnetic field along the wire, then the direction of the magnetic lines and the force can be determined using the Right Hand Rule.
electromagnetic force
The Electromagnetic Force is carried by the photon and is responsible for atomic structure, chemical reactions, attractive and repulsive forces associated with electric charge and magnetism and all other electromagnetic phenomena, just like gravity, the Electromagnetic Force has infinite range and obeys the inverse square law.
The Electromagnetic Force is more fragile than the energetic nuclear force, it is important to note that it is stronger than gravity, many Important scientists they are of the opinion that the Electromagnetic Force and the weak nuclear force are both aspects of a single force called electro depression force.
Before the invention of electromagnetism, people or scientists used to think that electricity and magnetism are two different subjects, the opinion changed after James Clerk Maxwell published a treatise on electricity and magnetism in the year 1873.
The publication states that the interaction of positive and negative charges is mediated by a force, this observation laid the foundation for electromagnetism, later many scientists such as Michael Faraday, Oliver Heaviside and Heinrich Hertz contributed their ideas in electromagnetism.
Magnet
Magnets are rocks or metals that create an invisible field around them, this field attracts other magnets and certain metals, the presence of a magnetic field is the reason why you can cover a metal refrigerator door with magnets.
A magnetic field is joined by the sides of the ends of the magnets, these ends are known as poles, all magnets have two poles, a north pole and a south pole, you can appreciate the magnetic force if you hold two magnets so that their poles are next to each other.
Magnets are made up of millions of molecules bound together in groups called domains, each domain behaves like a mineral magnet that has a north and south pole, with the same orientation of the domains, their strength combines, forming a larger magnet.
Iron has many domains that can be oriented in one direction, i.e. magnetize, the domains in plastic, rubber, wood and other materials are in a disordered state, their magnetic fields are multidirectional and therefore these materials cannot be magnetized.
The ancient Greeks were among the first people to discover iron, to them magnetism may have seemed magical, after all you can't see a magnetic field but its effects can be felt.
Over the past century, scientists have learned that the secret of a magnet lies in its structure. atomic, all objects in the universe are made up of atoms, each atom has a nucleus at its center, particles which are known as electrons orbit the nucleus.
This process creates magnetic fields around the electrons, magnetism occurs when the electrons rotate in the same direction, as all the electromagnetic forces of electrons, make the object a great magnet.
history of magnetism
Magnetism has been studied since ancient times and in the last two centuries it has become the basis of modern civilization, mankind accumulates knowledge about magnetic phenomena for at least three and a half thousand years (the first observations of electrical forces took place a millennium then).
Four hundred years ago, at the dawn of the formation of physics, the magnetic properties of substances were separated from the electrical ones, after which both were studied independently for a long time, therefore a foundation was created. experimental and theoretical theory that, in the mid-nineteenth century, became the basis for a unified theory of electromagnetic phenomena.
Most likely, the unusual properties of the natural mineral lodestone were known in Mesopotamia as early as the Bronze Age and after the appearance of iron metallurgy, it was impossible not to notice that lodestone attracts iron products.
The reason for this attraction was already thought by the father of Greek philosophy, Thales of Miletus (around 640-546 BC), which explained it by the special animation of this mineral. Thales also knew that amber rubbed on wool attracts dry leaves and small splinters, and thus endowed it with spiritual force.
The Greek poet Nikander mentioned the shepherd Magnis, who appeared by the rock, who drew the iron tip of his staff towards him, but this, in all probability, is simply a beautiful legend.
Later Greek thinkers talked about invisible pairs wrapping magnetite and iron and attracting them to each other, not surprisingly the word magnet itself also has Greek roots.
There is various information about the first mention of magnets, generally considered in the history of the ancient world in the context of a compass or religious cults, according to some estimates, lodestone or magnetic iron was first discovered in China four thousand years ago. of Christ.
It is noted that Western researchers tend to give priority to the discovery of magnetism to the ancient Greeks, the first mentions in the use of magnetic materials date back to the third millennium BC when the legendary Chinese emperor Huang-di used a compass during battle .
However, according to another version, he used the so-called south-pointing chariots, Chinese sailors of the end of the second millennium BC used a compass for sea navigation.
During the Middle Ages, the accumulation of new knowledge and theories about the nature of magnetism was practically absent, only the monks made some theological assumptions, but in the folk art of various countries, magnetic mountains or islands were sometimes mentioned that can attract all metal objects.
According to one of the European legends, a poor jeweler, Flavio Joya, invented a magnetic compass to marry the daughter of a rich fisherman, Domenico, the father did not want such a son-in-law and established the condition to learn to swim in a straight line in the fog at night.
The ingenious jeweler noticed that the cork with a magnetic stone on it, placed in a cup of water, always oriented in one direction, and managed to complete a difficult task, in fact, the jeweler was the papal secretary Flavio Biondo, who in 1450 described the knowledge of the inhabitants of Amalfi about the compass.
magnetic field and magnetic flux
These magnetic fields are vector fields in the population of magnets, electric currents or inconstant electric fields, in which magnetic forces are visible, a magnetic field originates from stirring electric charges and intimate magnetic periods of basic particles related to an essential quantum membership known as spin.
The magnetic field and the electric field are connected to each other and are devices of the electromagnetic power, one of the four Fundamental Forces of Nature.
The problem is that we cannot detect the magnetic field with our own senses, so we must use a compass to help us "see" the field, a compass is nothing more than a small magnet suspended so that it can rotate freely in response to a magnetic field.
Like all magnets, the needle has a north and south pole that are attracted and repelled by the poles of other magnets, when the compass is placed in a strong magnetic field, the forces of attraction and repulsion rotate the needle until it aligns perfectly with the direction of the field.
For our experiment, we are going to imagine that we have a bar magnet the size of a school bus sitting in an open space. This should help you visualize walking around the magnet and convince you that we are dealing with a very strong magnetic field! With the compass in hand, we will start next to the north pole and note the orientation of the needle.
What we would see is that the needle is pointing straight out and away from the magnet, if we were to start walking in the direction the needle was pointing, we would find that as we moved away from the pole, the needle would start to turn to the side, continuing the needle, we would eventually walk around the magnet and reach the south pole, here, the needle would point directly at the magnet.
Magnetic flux is defined as the number of magnetic field lines passing through a closed surface, due to the measure of the total magnetic field passing through a given surface area, here, the area under consideration can be of any size and under any orientation with respect to the direction of the magnetic field.
Faraday's great ideas lay in finding a simple mathematical relationship to explain the series of experiments he performed on electromagnetic induction.
Faraday made numerous contributions to science and is widely known as the greatest experimental scientist of the XNUMXth century, before we start appreciating his work, let us understand the concept of magnetic flux which plays an important role in electromagnetic induction.
To calculate the magnetic flux, we consider the field line image of a magnet or the system of magnets, as shown in the image below, the magnetic flux through a plane of area given by A that is placed in a field Uniform magnetic field of magnitude given by B is given as the dot product of the magnetic field and the area A.
The magnetic properties of matter
All matter exhibits magnetic properties when placed in an external magnetic field, even substances such as copper and aluminum not normally thought of as having magnetic properties are affected by the presence of a magnetic field such as that produced by either pole of a bar magnet.
Depending on whether there is an attraction or repulsion towards the pole of a magnet, matter is classified as paramagnetic or diamagnetic, respectively. Some materials, especially iron, show a strong attraction towards the pole of a permanent bar magnet; Materials of this type are called ferromagnetic.
In 1845, Faraday became the first to classify substances as diamagnetic or paramagnetic, he based this classification on his observation of the force exerted on substances in an inhomogeneous magnetic field.
Substances for which the magnetic susceptibility is positive are classified as paramagnetic, in some cases (including most metals) the susceptibility is independent of temperature, but in most compounds it is strongly dependent on temperature, increasing at as the temperature drops.
Below this temperature, the material exhibits spontaneous magnetization, that is, it becomes ferromagnetic, its magnetic properties being very different from those of the paramagnetic or high-temperature phase.
In particular, although its magnetic moment can be changed by applying a magnetic field, the value of the moment reached in a given field is not always the same, it depends on the previous magnetic, thermal and mechanical treatment of the sample.
In matter of free magnetic dipole moments, the orientation of the moments is normally random and as a result, the substance has no net magnetization, when a magnetic field is applied, the dipoles are no longer completely randomly oriented; more dipoles point with the field than against the field.
When this results in a net positive magnetization in the field direction, the substance has a positive susceptibility and is classified as paramagnetic, there is a third category of matter in which intrinsic moments are not normally present, but appear under the influence of an external magnetic field.
Magnetic hysteresis curve
The phenomenon of the flux density B lagging behind the magnetizing force H in a magnetic material is known as magnetic Hysteresis, The word hysteresis is derived from the Greek word hysterein which means to fall behind.
In other words, when the magnetic material is magnetized first in one direction and then in the other direction, completing one magnetization cycle, the flux density B is found to lag behind the applied magnetizing force H.
https://youtu.be/BL4F-Afugio
There are various types of magnetic materials, such as paramagnetic, diamagnetic, ferromagnetic, ferromagnetic and antiferromagnetic materials, ferromagnetic materials are mainly responsible for the generation of the hysteresis loop.
When the magnetic field is not applied, the ferromagnetic material behaves as a paramagnetic material, this means that in the initial stage the dipole of the ferromagnetic material is not aligned, they are placed randomly, as soon as the magnetic field is applied to the ferromagnetic material , their dipole moments align in a particular direction as shown in the figure above, resulting in a much stronger magnetic field.
The magnetic field created by an electric current
An electric current in a long straight wire produces a magnetic field whose field lines are formed by circles centered on the wire, this magnetic field can be detected by placing a magnetic compass near the wire, the direction of the magnetic field B can be determined by right hand rule.
To produce a stronger magnetic field using electric currents, several loops are grouped together to form what is called a solenoid, a solenoid produces not only a strong magnetic field, but also a uniform one with a north pole and south pole similar to magnets. .
Solenoids have many applications, the magnetic field produced by solenoids can be controlled by controlling the current in the solenoid, the current in the solenoid can be turned on or off and also by increasing or decreasing the electrical current in the solenoid we can control the strength of the field. magnetic produced.
The Electromagnetic Force, also called the Lorentz force, explains how stationary and moving charged particles interact, it is called electromagnetic force because it includes the previously distinct electric force and the magnetic force, the magnetic forces and the electric forces are really the same fundamental force, the Electromagnetic Force is one of the four fundamental forces.
Einstein developed his theory of relativity from the idea that if the observer moves with the charged particles, the magnetic fields are transformed into electric fields and vice versa, a special case of the Electromagnetic Force, when all charges are point charges. (or they can be divided into point charges), is Coulomb's law.
Faraday-Lenz, electromagnetic induction
Lenz's law of electromagnetic induction establishes that the orientation of the current induced in a conductor by an inconstant magnetic field is such that the magnetic field created by the caused current faces the initial variable magnetic field that produced it, the direction of this current flow is given by Fleming's right-hand rule.
This can be difficult to understand at first, so let's look at an example problem, remember that when a magnetic field induces a current, the magnetic field that produces this induced current will create its own magnetic field, this magnetic field will always be such that it opposes to the magnetic field that originally created it.
When the magnetic field "B" is decreasing, the induced magnetic field will again oppose it, but this time "opposing" means that it is acting to increase the field, since it opposes the decreasing rate of change.
Lenz's law is based on Faraday's law of induction, Faraday's law tells us that a changing magnetic field will induce a current in a conductor, Lenz's law tells us the direction of this induced current, which opposes the field initial changing magnetic field that produced it, this is indicated in the formula for Faraday's law by the negative sign.
Electromagnetic induction in a coil
One of Faraday's experiments in that important year featured a permanent magnet and galvanometer connected to a coil of wire wound around a paper cylinder, similar to those illustrated in this tutorial.
To simulate Faraday's experiment, drag the bar magnet back and forth within the coil, notice that the voltmeter connected to the coil only indicates the presence of a current when the magnet is actually moving, and that its needle moves. it deflects in one direction when the magnet is moved towards the coil and in the opposite direction when the coil is dragged.
Also note the magnetic field lines, depicted in blue, emanating from the magnet, and how the direction of the current changes depending on which way the magnet moves.
As you can see, when the north end of the magnet enters the coil, a current is induced that travels around the coil in a counterclockwise direction, when the magnet is pulled out of the coil, the direction reverses clockwise.
Also note that the current produced is stronger when the magnet is moved rapidly rather than gradually, adjust the number of turns slider and move the magnet in and out of the coil again to determine the ratio of the turns of wire in the coil. coil and the current induced in that coil.
As the voltmeter indicates, a higher voltage can be induced in coils made from a greater number of turns of wire, use the blue button on the magnet to see how things change when the south end of the magnet, exhibiting different field lines, interacts with coils of wire.
In this demonstration of electromagnetic induction, the mechanical energy of the moving magnet is converted into electricity, because a moving magnetic field, entering a conductor, induces current flow in the conductor, what also happens is that the current that has been induced in the wire, in turn, generates another magnetic field around the wire.
Eddy currents
Eddy currents are currents that pass through conductors like eddies in a current, they are caused by changing magnetic fields and flow in closed loops, perpendicular to the plane of the magnetic field.
They can be created when a conductor moves through a magnetic field, or when the magnetic field around a stationary conductor changes, i.e. anything that causes the conductor to experience a change in the strength or direction of a magnetic field. can produce eddy currents.
The size of the current is in accordance with the size of the magnetic field, the area of the loop, and the rate of change of the magnetic flux, and is inversely proportional to the resistivity of the conductor, just as any current that distills through a conductor, a current parasite will produce its own magnetic field.
Lenz's Law states that the direction of the magnetically induced current, like an eddy current, will be such that the magnetic field produced will oppose the magnetic field change that created it.
This resistance set up by the opposing magnetic fields breaks down in eddy current braking, which is commonly used as a method of stalling rotating power tools.
Examples of Electromagnetic Force
The most common examples that can be mentioned are the following:
- All light from the Sun and other sources consists of photons that are carriers of Electromagnetic Force.
- Magnets and the Earth's magnetic field, which protects us from harmful radiation, are aspects of the Electromagnetic Force.
- Gamma radiation is an electromagnetic mechanism that allows an atomic nucleus to lose energy, according to the Thomson Atomic Model.
- Electrostatic repulsion between like charges has prevented the Sun from rapidly fusing all of its Hydrogen.
- The Electromagnetic Force, which also has a wide range, is the most diverse and influential of all the fundamental forces.
