How the fuck do magnets work

kremlint:

you could take every word ive ever written on this blog and it still wouldn’t be enough to properly explain how a normal bar magnet works

seriously

it was the dead last topic after 4 semesters of physics for electrical engineers

let’s give this a quick shot

kindergarten

magnetism is a phenomenon exhibited by things that produce magnetic fields. magnetic fields are phenomenons created by moving electrical fields. electrical fields are phenomenons created by imbalances between positively-charged entities (protons) and negatively-charged entities (electrons)

that is to say: for a given volume, if there are more protons than electrons, that volume emits a positive electrical field; it will repel other positively-charged entities and attract negatively-charged entities

6th grade science class

bar magnets are obviously made up of atoms which are made up of protons & neutrons in the nucleus; and electrons circling the nucleus some distance away. the number of protons in the nucleus will always match the number of electrons orbiting the nucleus, and because a proton exhibits a +1 charge and an electron exhibits a -1 charge, these forces cancel out and atoms remain nicely balanced, neutral entities

8th grade science class

electrons don’t just wildly fly around nuclei like moths around a lightbulb. electrons are negatively charged, and repel each other, so naturally they take the path of least resistance, orbiting in a path that most-avoids the other electrons. these are called orbitals and they a defined list of paths that electrons will travel around any nucleus, regardless of size or any other factor

senior high school physics class

like i said before, a magnetic field is simply a moving electric field. if you zoom in real close and look at a single electron, you will see a single point charge emitting a negative electric field

now

electrons move very, very fast when they are orbiting a nucleus. as they are both moving fast and have an intrinsic electrical charge, they create an intrinsic magnetic field. now, if they are apart of an atom made up of a number of protons that just-so-happens to be equal to the maximum number of electrons that can fill an orbital, you get a very non-magnetic atom. an example is helium, a helium atom has exactly two protons and exactly two electrons, and the first orbital (the s orbital) can contain only 2 electrons, you have both slots of the s orbital filled. the reason this atom is so non-magnetic is that inside the orbital, both electrons are spinning around the atom in opposite directions (one clockwise, one counterclockwise) and their intrinsic magnetic moments cancel out because they are geometrically perpendicular. just like with electric fields we have positive charges and negative charges, with magnetic fields we have north poles and south poles. same idea, like charges/polarities repel & opposing charges/polarities attract

university sophomore year electromagnetism/physics class

atoms (like iron) that happen to have a number of protons that is nowhere near the bounds of electron capacity per orbital naturally have unbalanced orbitals as whatever outermost orbital is only half-filled or about half-filled. these kinds of atoms have the capacity to also be super magnetically imbalanced, as with a only-half-filled shell you might have each of the outermost electrons spinning in the same way (and because the other half of the electron “slots” in that orbital aren’t filled, you won’t have anything opposing it leading to a net charge on the atom).

you should understand two things about metal before i continue:

(1) metals tend to form crystalline atomic structures. if you take a look at the atoms constituting a big hunk of iron, you will see them aligned in a “grid”-like structure. it won’t be an amalgam of nebulous unorganized particles, it will be an organized, structured shape made up of the same tessellating pattern repeated

(2) metal atoms form magnetic bonds with other metal atoms in their vicinity. these bonds are special because the electrons of one metal atom can very easily move to another atom, and be replaced by incoming electrons from other atoms. in any given contiguous piece of metal, all the electrons are constantly swimming around between nuclei and this is what binds them together

ok, so 

if you take a ferromagnetic metal, meaning a metal that is in that sweet spot of “i only have half my outermost orbital filled” that also happens to have all those outermost electrons spinning in the same way (exhibiting like polarity) you have an atom with an unbalanced net magnetic charge that is pointing in some direction. this direction will tend to be the same for all atoms surrounding it to some extent due to the organized crystalline structure. this leads to the idea of magnetic domains which are contiguous fragments of a body of metal that all point in a certain domain themselves, but not necessarily all domains pointing in the same direction:

when you place a magnet on a ferromagnetic piece of metal, you will align these domains so that they all point in the same direction. when this happens, you actually get a magnet because you will have electrons moving around in a circle 

quantum physics graduate PhD candidate writing thesis

if you’ve been following closely, you’d realize that even at this point a bar magnet couldn’t exist. why? go back to kindergarten: 

that is to say: for a given volume, if there are more protons than electrons, that volume emits a positive electrical field; it will repel other positively-charged entities and attract negatively-charged entities

in a bar magnet, there are an equal number of positive charges as negative charges. sure, the negative charges (electrons) might be moving around, but because of this equality and because all the charges are “well mixed”, there is no electric field. if there is no electric field, there can’t be a magnetic field either (although at this point i can say that electric fields and magnetic fields are two ways of understanding the same thing)

so what the fuck, right?

the answer has to do with special relativity. special relativity is a term that tends to scare people off for some dumb reason and you should understand that if you take it slowly it is dead simple

special relativity is part of what einstein is famous for, it basically states that neither space nor time are absolute. how long something takes or how wide something measures out to be isn’t the exact same from every frame of reference. if you are in a satellite traveling literally miles per second (ground speed) around the earth, and you look down at earth and measure how long a traffic light takes, that time will be shorter than how long someone standing next to it would measure. similarly, if you are standing on earth and look up at the satellite, it will look skinnier than it would look were you standing on it

that’s all special relativity is

SO, in the context of a magnet, we are at the point where we understand a bar magnet to be a piece of metal whose electrons are moving in a circular fashion for the most part. the electrons are moving from nuclei to nuclei, the nuclei themselves are staying put

there is a velocity disparity between the observer (nuclei) and the subject (electrons). this makes it seem, from the nuclei’s point of view, that the electrons are actually skinnier than they would appear were they standing still (due to length contraction) and because of this, more electrons “fit” in this pipeline of electrons that circles the metallic body. these “extra” electrons now outnumber the protons locally extant and you have now a charge imbalance, resulting in an electromagnetic field