Magnetism

If you've ever wondered why a paperclip sticks to a bar magnet, then you've likely experienced magnetism before. The same goes for if you've ever put a fridge magnet on your fridge door; these are all forms of one unifying concept known as magnetism, which is one part of the unifying theory of electromagnetism. In this article, you will hopefully learn a little bit about the dynamics behind magnetism and magnets themselves.

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Magnets are just objects that create/produce magnetic fields themselves. All magnets are dipoles, which means they have a north and a south pole, no matter how small the magnet itself is.

A fundamental property of electrons is that they carry magnetic dipole moments, which we'll elaborate on later. What this means is that electrons essentially behave like tiny magnets in and of themselves. These electrons have magnetic dipole moments, which mean they take on specific orientations near an applied magnetic field, similar to how their charge causes them to react to applied electric fields.

This dipole moment is dictated by the quantum spin of the electron(and to some extent, its angular momentum around the atomic nucleus of the atom) and is either -1/2 or +1/2 in a pair according to the Pauli Exclusion Principle.

Because the two electrons in an electron pair have opposing spins, their magnetic dipole moments cancel out. This means that if an atom were to have an unpaired electron, that electron's spin won't get canceled out so that atom will react to an applied magnetic field. As we take more and more atoms like this, their net magnetic dipole moments add up to create a macroscopic effect of magnetism. This effect is known as paramagnetism: when an atom aligns in parallel to a magnetic field due to having an unpaired dipole. You may be wondering that if many atoms have paramagnetic abilities, why aren't most objects magnetic? This is because the magnetic forces on paramagnets are extremely weak and you need a magnetic field much stronger than even Earth's to see noticeable attractions.

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Examples of paramagnets are aluminum, oxygen, titanium, and Iron Oxide(FeO)

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Diamagnetism is experienced by all elements and is inherent to every atom. However, diamagnetism is even weaker than paramagnetism which means that if an atom has an unpaired electron in a shell, that atom's paramagnetism will exceed its diamagnetism, making the atom primarily paramagnetic. Diamagnetism is the parallel magnetic repulsion of an atom in proximity to an applied magnetic field.

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Ferromagnetism is caused in almost the same way paramagnetism is caused except in select substances, like iron, nickel, cobalt, their alloys, and a few compounds with rare-earth metals, the magnetic dipoles create their own magnetic fields. The distinction that causes these elements to be ferromagnetic and similar elements not to be ferromagnetic is the fact that in purely paramagnetic elements, the thermal motion of the electrons causes randomization in their spin orientations, excluding them from the ability to bear ferromagnetism. Because ferromagnets have the magnetic dipoles spontaneously generate their own magnetic fields, this means that they don't need to be in proximity with another magnetic field to show their relative magnetism; they can create that magnetic field themselves.

A magnetic field is a field that describes how objects interact magnetically. It can be thought of as similar to a force field, like a gravitational field, as it effectively dictates how objects that impose magnetic forces affect other objects. The SI unit for magnetic field is teslas. Smaller magnetic fields can be measured in gausses, where 1 Tesla = 1000 Gausses. Magnetic fields are represented through lines just like other fields and they go from the north end of a given magnet to its south pole.

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Magnetic fields are created by currents. This may seem confusing but if you think about the relationship between electricity and magnetism through moving charges. Since magnetism is created by moving charges and we see later that magnetic forces are created by magnetic fields, then magnetic fields must be created through moving charges, which is another term for current. This current can range from the small currents given off by electrons moving around in their respective atoms to the large currents given off by macroscopically sized wires.