Hi everyone and welcome to the new Megathread :) For my first Mega I want to share a special interest of mine: the magnetic field and how to understand its behavior intuitively.
I'm guessing most of us have played with magnets before at some point and have felt that mysterious force pushing them apart or pulling them together, depending on how the magnets are oriented toward each other. Some of you may have also seen diagrams like this
Or done an experiment where you visualize the magnetic field lines with iron filings like this
These lines represent the shape of the magnetic field. The way you can interpret them is that if you place a compass in the field, the compass will align with the field lines at that point. And the closer the lines are to each other, the stronger the magnetic field is in that area. Also, magnetic field lines always form closed loops. They appear to end at the poles of a magnet, but actually they continue on inside the magnet. They do however exit/enter the magnet at the poles.
"But Witchy," you may ask, "why are the lines so concentrated at the poles but then they spread out so much as they travel from one pole of the magnet to the other?" Excellent question my theoretical student XD.
This is I think the key point that was a bit of a eureka moment for me when I realized it a long time ago when I was studying this stuff: the magnetic field lines "want" to be as short as possible while also "wanting" to be as far apart as possible. And when I say want, it does actually behave a little bit like a desire, as the magnetic objects in this field will experience a magnetic force tryin gthe move the object to spread out the field lines and make them shorter.
Let's use this picture I grabbed from Wikipedia as an example:
the bar magnet creates a strong magnetic field at the poles, which means lots of magnetic field lines are squeezed closely together at the poles where they enter/exit the magnet. These lines don't want to be so tightly packed together, so they immediately start spreading out but also immediately start curving towards the opposite pole to try to keep the distance short. If you then try to bring the north pole of another bar magnet close to the north pole of this one, both have magnetic field lines coming out trying to get to their respective south poles, but now even more tightly packed together as you bring the magnets together. Since the magnetic field lines don't want to be so close together, both magnets experience a force pushing each other away so that the magnetic field lines aren't being pushed together so tight.
Similarly, if the south pole of one bar magnet is brought near the north pole of another, the magnetic field lines exiting the north pole of one want to go to the south pole, but the closest south pole is the south pole of the other magnet being brought close, so now the lines go through both magnets before looping back around:
However, between the closest poles of the two magnets, the lines are still concentrated but will try to spread out between the poles. Since the lines want to be as short as possible and don't want to spread out, the magnetic field exerts a force on the bar magnets pulling them together, since that would shorten the lines between the poles down to pretty much nothing.
Finally, a few of you may have been wondering what determines how much the magnetic field lines want to spread out vs shorten. These two tendencies are in opposition pretty much all the time, since spreading the lines out more requires making them longer. This is determined by something called the magnetic permeability which is a property of the materials that the field is passing through (even air or a vacuum). High permeability materials tend to concentrate the magnetic field lines more and allow them to get shorter, while low permeability materials tend to force the lines to spread out and lengthen. Examples of materials with high permeability are iron, cobalt, and other magnetic or ferromagnetic materials. Low permeability are pretty much anything that doesn't experience force in a magnetic field, so most things.
Post thumbnail attribution: (By Omegatron - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=640068)
Anyway I hope some of you enjoyed this rant or find the information here useful. I can talk about magnets all day so feel free to hit me up if you want, though my inbox will be overflowing for the next week I'm guessing.
Enjoy the Mega!
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frustrated rambling
There are days where I feel I love teaching, and then there's days like today when I put so much effort in only to be shat on by students. Is it patronizing to give study tips for a final that's coming up? I uploaded all of the quizzes we took this semester (we took one every week) as well as all of the keys I made and told them I recommended downloading quizzes they struggled with, timing themselves, and working them through without notes, and only once giving it a solid try going back and reviewing the stuff they missed. And I got so many eye rolls, and I heard one person behind me say "nah it's fine. he (I'm not out to my class) doesn't know who I am" and I turned around and they'd snapped a picture of me and were writing a caption for social media. I have one specific table that is great but it's like I did something for everyone else to hate my guts. I try so hard not to take this stuff personally but this semester has been so hard
Ugh students can be awful. Sometimes they’ll just hate you because they struggle with your class and think it’s your fault. You can only do so much as a teacher in current circumstances because you have very limited time and resources per student. Which means you’re doomed to fail some students.
I remember teachers giving study tips when I was in school and I’d often ignore them because I wasn’t organised like that. I often spent minimal time studying for a test because I always came home from school with negative energy and most of the tips required more work for which I was too tired.
That doesn’t mean it’s a bad thing to do though, there are students that will benefit from the advice.
spoiler
No, I feel like this is something that could only be seen as a positive thing that would help students. If they didn't want to do it, they didn't have to, there's no need to give you such a rude reaction OR to...
This is legitimately one of the biggest anxieties I have about going into teaching. I was just thinking about this, today, because what exactly can be done in that situation? These kind of things would piss me off so much and make me so uncomfortable, and yet there doesn't seem to be a solution.
I'm sorry that you have to deal with that kind of behavior
. Even if someone doesn't like a teacher it's certainly not a reason to be disrespectful like that, especially to the teacher's face, and it's even more so not a reason to take pictures or record videos without the teacher's consent and proceed to put them on the internet.
This is my fourth semester teaching and it has never been this bad. I've had such wonderful experiences up to this point. I think it's either the fact that I got assigned the 6pm section and they all hate being there, or this group in particular sees me as less than qualified to teach because I'm just a graduate assistant.
I've heard that a lot of 2020 pandemic students who were in early education (like kindergarten to grade 2) are really shitty because they essentially lost 2 years of socialization that would've nipped the shite attitude in the bud. So they're slowly wriggling their way up and it's making very teacher miserable as they have to take on the task of this shitty cohort until one day they get dumped onto the labour force. Or they go NEET, who the fuck knows at this point
Sometimes you just get shit class. I still remember the class from hell early in my career. It never happened again, so sometimes you just have to suffer it