Never too old to learn

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This is now a rare brainlet pic thread

got any more?

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>magnets

Unironocally asking, how tf can permanent magnets keep lifting more and more stuff? Where does the energy come from?

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A very Veeky Forums one

Magnets are counterintuitive because most people confuse a constant force with constant work. A constant force doesn't require energy; you know this because gravity constantly applies a force on you, but you're never flattened against the earth's crust.

If the magnet were to do work on something, that would mean that it changed the momentum of an object, ergo, its energy.

This is my rudimentary understanding of magnets. Please correct me if I'm wrong.

I get that they don't do work once you picked up a paperclip for example.

However, after picking up one you can rake your magnet plus paperclip system and go pick up another one.

All explanations on this I've gotten so far have been some shady 'magneto hydrodynamic and weird quantum effects' handwavy explanations but no real results.

Only concerned with permanent magnets, electromagnet obviously take the energy from the current flow through them.

So the thing with permanent magnets is that they're made of metals that would normally create a small magnetic field without an electrical impulse. In normal circumstances, iron, for example is made of these materials although the fields are poorly aligned and will cancel one another rendering the object magnetically inert.

Permanent magnets are created when materials chock full of these tiny magnetic field inducing elements (iron) are turned molten, and subjected to an external magnetic influence. This forces the fields to align. I'm not well versed on the math, but the math asserts that each of the tiny fields, when aligned, will combine into one big one.

Hope this helps.

I'm not a physicist but I think the simple explanation is the lining up of charged particles in a material so that the entire material has a dipole moment. Cause you know electrons have charges and stuff which is based on quantum physics.

So every time you pick up something the overall field of the magnet decreases?

Then how come you can just keep picking up stuff with your magnet?

This is where my knowledge of magnets ends, sadly. My intuition tells me the answer is yes and the reason why is because you can only pick up so many paperclips with a given magnet before it's not attractive enough to pick up any more.

Again, no clue this is just my ass talking.

Hmm, my intuition was that the magnetic domains get disturbed while picking up something but then realign afterwards making you able to pick up another one, all without fancy quantum magnetohydrodynamics, but I'm not sure that is possible at all. Been asking around to literally every physicist i see and noone has a satisfying answer.

These pictures are hilarious.

Perhaps. Why not take an E and M class?

Because I did take 2 already but magnetism isn't really discussed until stat mech (which I also took twice already) but it seems permanent magnets are just something physicists like to not think about.
I'll probably see if I can figure out something myself but have to say that statmech is probably my weakest subject so I'm not too confident in myself

Because the reduction in field alignment is miniscule.

What's there to understand? Changing magnetic flux generates a current who's magnetic field opposes the change in flux.

What if you think you about infinitely many paperclips, will you be able to keep picking up more and more or will the field eventually break down? As in, will the domains realign if you give them enough time or will you eventually just have a non-magnet? In that case, the whole system should collapse, the paperclips fall down and your magnet magically becomes magnetic again from the released energy?

Infinite paperclips require infinite energy, so yes the magnet eventually stops being able to pick them up. The magnet is exerting a torque on every unaligned spin in the paperclip, decreasing its energy over time. It gets some of this energy back when you put energy into the system to pry apart the paperclip and the magnet, but not all of it.

Interesting. So if I look at a magnet, paperclip and thermal bath, I would be able to pick up as many paperclips as I want? Since the extra energy comes from the external bath, right?

In the case of no interaction with a heatsink, would that be a feasible way to measure the energy stored in the magnet?

I have a scholarship from doing pure math and applied math yet if you give me a fucking combinatorial question I'll shit my pants I'm such a fucking dumbass

How about post topics you are interested in but too lazy to study and research?

>biology

kek

...for ants!

Lifting line theory.

Uh, no. The stored energy in a magnet is just an integral

U_m = (1/2m) int(B^2)dV over the volume that includes every magnetic field line (all space), m is the vacuum magnetic permeability.

The energy used to pick up the paper clip is magnetic, and the only thing the thermal bath provides is heat, which actually contributes to demagnetization. You could pick up infinite clips if you had an infinite current.

Optics

But a permanent magnet does not have any current at all, that's the whole point I was trying to make.

With electromagnets I know this is not a problem, since you could just supply more current.

But what about a permanent magnet? It has magnetic domains which due to their electron configuration and spin alignment produce a macroscopic magnetic field (corect me if this is wrong pls) but no current inside it.

May be able to help you on that, what do you not understand? Just classical geometric optics?

What about it? My master's is in optical engineering.

AP biology
gave up because all the work

In physical optics. Couldn’t understand anything, diagrams and figures in the textbook made no sense, and teacher went over it really briefly. I just rememorized formulas and was able to do good on the test and exam. This was grade 12.

I’m in first year computer engineering so I have to take electricity and optics in second semester any resources you would recommend?

Fundamentals of Photonics by Saleh and Teich is pretty much all you'll ever need to know about optics/optoelectronics from an engineering persepective.

For a more fundamental understanding look at the feynman lectures on optics (part of e&m iirc).

They were hosted for free by some uni last time I looked

>mfw I TA'd calculus II for an entire semester without anybody catching on to the fact that I can't integrate by parts

Trust me, they caught on but we're afraid of you grading

>to stupid to analyze algorithms

honestly I slept through the induction part of physics class and still got an A in it
no idea how the fuck magnets or electricity works tho

>chemistry
it's like algebra but spoken in a language i don't understand

i aced phys I last year, only didnt understand tension

taking AP phys this year, literally understand none of it but manage by shitting equations into paint. its online so i havent been using pencil and paper but i still expected more from myself

Tension is just the force pulling on a rope from both ends, consider each end like a force acting on whatever you have on it, if the string is inelastic, the force on both ends has to be the same.

I have trouble understanding the path integral formulation of QM.

Wojak is better than pepe

Wojak is definitly the face of Veeky Forums , between brainlet wojak and too intelligent wojak.

Sorry, that's just i wanted to say.

ofc he isnt a neonazi icon

[math]\color{orange}{\mathfrak{WHY\ THE\ ANTI-SEMITISM?}}[/math]

[math]\color{orange}{\mathfrak{lmao this one is genius}}[/math]

Induction is pretty easy. Think of it as how a current and magnetism feed off of each other.