In this article, we are going to discuss what is magnetism? definition, history, and its development. So let’s get started…
What is magnetism?
We know that when an electric charge moves it produces electric and magnetic fields. The production of a magnetic field means that the charged particles are now behaving like a magnet, and we know that a magnet has the properties of attraction and repulsion. It can attract and repel any other magnetic material. So what is magnetism?
| Magnetism is defined as the attractive and repulsive phenomenon shown by the moving charges. The region around the moving charges consists of both electric and magnetic fields. |
Magnetism is a class of magnetic phenomenon that is described by magnetic fields. Magnetic fields can be created by the electric current and the magnetic moment of the elementary particles and can act on the other electric current and magnetic moment.
Above we have defined magnetism as the attractive and repulsive phenomenon shown by the moving charges. On the basis of this definition, we can say it is one aspect of the combined phenomenon of electromagnetism. The most familiar effects of magnetism occur in ferromagnetic materials, which are strongly attracted towards the magnetic fields and can be magnetized to become permanent magnets (types of magnets that produce their own magnetic fields.)
If magnetizing of the magnet is possible then de-magnetizing of the magnet is also possible. There are a few substances that are ferromagnetic in nature. The most common ferromagnetic materials are iron, cobalt, and nickel and their alloys. But the rare-earth metals such as neodymium and samarium are less common examples of a ferromagnet. The prefix Ferro- means iron, because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, Fe3O4.
Types of magnetism
Almost all substances exhibit some type of magnetism. Magnetic materials are categorized according to their bulk susceptibility. Ferromagnetism is responsible for most of the effects of magnetism that we are encountered in everyday life, but there are actually many types of magnetism other than this.
Paramagnetic substances, such as aluminum and oxygen, are weakly attracted towards an applied magnetic field. Diamagnetic substances, such as copper and carbon, are weakly repelled by the applied magnetic field, while antiferromagnetic materials, such as chromium and spin glasses, have a more complex relationship with a magnetic field.
The magnetic force experienced by the paramagnetic, diamagnetic, and antiferromagnetic materials are generally too weak to be felt and can be detected only by laboratory instruments, so in everyday life, these substances are often described as non-magnetic substances.
The magnetic state (or magnetic phase) of a material depends on temperature, pressure, and the applied magnetic field. A material can exhibit more than one form of magnetism if these variables change.
The strength of a magnetic field is inversely proportional to the square of the distance between the point and the source and it always decreases with distance, though the exact mathematical relationship between strength and distance varies. Different configurations of magnetic moments and electric currents can result in complicated magnetic fields.
Magnetism history and development
The concept of magnetism was first to arise in ancient times when people noticed that the lodestones, naturally magnetized pieces of the mineral magnetite Fe3O4, could attract iron. The word magnet comes from the Greek word magnētis lithos, which means Magnesian stone or lodestone.
In ancient Greece, philosopher Aristotle attributed the first scientific discussion of magnetism to the philosopher Thales and Miletus who lived around 625 BC to about 545 BC. In the ancient Indian medical text Sushruta Samhita, it is discussed that how magnetite can be used to remove arrows embedded in a person’s body.
The evidence of Magnetism is also found in ancient china, the first literary reference to magnetism found in a 4th-century BC book “Guiguzi” which is named after its author “Guiguzi”. Lüshi Chunqiu, 2nd-century BC annals also notes that “a lodestone can attract iron, seems like that some (force) is attracting it.
The earliest mention of the attraction of a needle by a lodestone found in the 1st-century work Lunheng (Chinese classical text which contains critical essays on natural science and Chinese mythology, philosophy, and literature.): “A lodestone attracts a needle”.
Shen Kuo was the first Chinese scientist of the 11th century to write—in the Dream Pool Essays—of the magnetic needle compass and that it improved the accuracy of navigation by employing the astronomical concept of true north. By the 12th century, the Chinese were known that how to use the lodestone compass for navigation? They made a directional spoon from lodestone in such a way that the handle of the spoon was always directed in the south.
In 1187, Alexander Neckam was the first person in Europe who describe the compass and its use for navigation. In 1269 Peter Peregrinus de Maricourt wrote the Epistola de magnete, the first existing treatise on the properties of magnets. In 1282 the properties of magnets and dry compasses were discussed by Al-Ashraf Umar II, a Yemeni physicist, astronomer, and geographer.
Trattati sopra la natura, e le qualità della calamita, is the only existing work by Leonardo Garzoni, which is the first known example of a modern study of magnetic phenomena. Written in the early 1580s and never been published, this treatise became widely used at that time, Niccolò Cabeo describes Garzoni as an expert in magnetism, whose Philosophia Magnetica (1629) is just a re-adjustment of Garzoni’s work. Garzoni’s treatise was also known by Giovanni Battista Della Porta. [latexpage]
In the year 1600, William Gilbert published his research work titled “De Magnete, Magneticisque corporibus, et de Magno Magnete Tellure” (About the magnet and the magnetic bodies and about the great magnet, the earth). In this work, he comprehensively describes many of his experiments with his model of the earth called the terrella. From his experiments, he concluded that the earth itself was a great magnet and so that the compasses, therefore, pointed north (some earlier believed it was the Pole Star (Polaris) or a large magnetic island at the North Pole that attracted the compass).
The main understanding between electricity and magnetism started with work by Hans Christian Ørsted in the year 1819, Ørsted was a professor at the University of Copenhagen, who discovered the accidental deflection of a compass needle when it is placed near a current-carrying wire. From this experiment, he proposed that an electric current could create a magnetic field. This groundbreaking experiment is known as Ørsted’s Experiment. Several other experiments were performed by André-Marie Ampère, who in 1820 discovered that the magnetic field circulating in a closed path was related to the current flowing through a surface enclosed by the path, and gave a law called ampere circuital law. $$\oint_{C}{B\cdot dl}=\mu_0 I$$
In the same year of 1820, Carl Friedrich Gauss, Jean-Baptiste Biot, and Félix Savart, both of whom came up with a law called Biot–Savart law, which gives an equation for the magnetic field from a current-carrying wire at a point outside the wire.
Michael Faraday, who discovered in 1831 that a time-varying magnetic flux induced a voltage in a loop of wire, and other physicists found other connections between magnetism and electricity. James Clerk Maxwell synthesized and expanded this knowledge into Maxwell’s equations to unify electricity, magnetism, and optics in the field of electromagnetism. In 1905 Albert Einstein used these laws to build a foundation for his special theory of relativity and required that the laws apply in all inertial systems.
And in the 21st century, the concept of electromagnetism is still continued to develop. Physicists still working in the field of electromagnetism to find new theories and laws.
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