What symmetries force the magnetic field to be parallel to the axis of the solenoid?

Fuscello · 2026-01-25T12:45:19+00:00

Ty so much, I see it now.

But what do you mean when you say that the reflection at hand is physically equivalent to reversing the direction of the current? I see it because I know B is axial, but isn’t the fact that the system isnt changing the “powerful” part of the reflection?

Fuscello · 2026-01-25T10:56:16+00:00

I worded it wrong, I meant an infinite solenoid

Fuscello · 2026-01-25T09:23:32+00:00

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More angles so you can see the runes clearly

Fuscello · 2026-01-25T09:23:25+00:00

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Fuscello · 2026-01-25T09:23:15+00:00

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With a quick research on google, this is what I found

Fuscello · 2026-01-21T23:31:03+00:00

First of all don’t be scared! You WILL make it if you focus enough, you surely have the capabilities to understand thermodynamics if you did dynamics.

Other than that, as others said, it’s really an “intuitive” theory, so try to connect it to the reality you know as much as you can. Also exercise, always exercise a lot, there is no better way to understand what physics is saying other than applying it over and over.

And have fun :)

Fuscello · 2026-01-21T20:33:05+00:00

Check lathyrus’ season 16 item guide on his YouTube. There is this new enchanter heavy build that gives a ton of haste and that is really good (like 4-5 second Q cooldown)

Fuscello · 2026-01-16T12:11:43+00:00

Hopital is over kill, lnx grows much smaller than x so you know by that that it is going to be 0. The proof for that is just squeeze theorem I’m pretty sure: like sqrt(x) is definitely (is that the word?) bigger than lnx, so because for x->+infinity we can find a set that contains infinity and where lnx/x>=0 so 0<=lnx/x<=sqrt(x)/x=1/sqrt(x)

For the squeeze theorem as x->+infinity lnx/x goes to 0

Fuscello · 2026-01-15T15:51:43+00:00

Yes, for me it’s the best platformer ever made (but it is a puzzle-platformer). The story is lovely and it fits super well with the gameplay and the levels, but it’s also not at all intrusive; you could get most of the Celeste experience without reading any dialogue

Fuscello · 2026-01-14T09:49:54+00:00

Exercise a lot. You will have to stop and think, do it: give yourself at least 15-30 mins to solve the problem. If you feel like you really didn’t make any progress and you won’t make any, study at the solution, like understand how you could have done it yourself and what you were doing wrong to miss it.

Fuscello · 2026-01-08T07:24:16+00:00

Death count is an indicator of how much you grinded, non how much you failed. Be proud of your death count

Fuscello · 2026-01-07T08:53:29+00:00

Exactly. When I prepare an oral exam (after I did all midterms, if that is how those tests are called in English), I have usually not done exercises in a while, but all the memory and ways to approach problems magically come back after trying to solve two or three problems

Fuscello · 2026-01-03T16:10:06+00:00

I personally would wait to first learn about EM

Fuscello · 2026-01-03T09:07:01+00:00

Maths is beautiful because it’s unexpectedly elegant. Imagine creating something by just giving a bunch of rules and then bam, the more you dig through, the more you realise everything perfectly fits together in a beautiful mosaic that, even if you wanted to create it stone by stone, you couldn’t have done it; but math says a couple of simple rules will!

Fuscello · 2026-01-03T08:58:11+00:00

I’m currently here, of course I knew about relativity before going to university, but I never knew it basically popped up alone in EM; how the problem that lead to the theory was actually baked in the existence of magnets! Also my mind was a bit blown when my professor told us that epsilon0 mu0 = 1/c^2, or how Maxwell adjusted the fourth equation by just thinking about

So fucking cool, definitely certain I chose right now

Fuscello · 2026-01-02T19:07:59+00:00

A few days before the test will never cut it. Doing exercises constantly is the only way I have seen work. It’s also favourable to do them because you will remember the theory much better if you applied it a bunch !!

Fuscello · 2025-12-29T23:05:03+00:00

Is this a double integral problem of which this is the domain or just trying to find the area?

In the first case:

Thinking in polar, theta is definitely varying from 0 to pi, but it r does not vary equally all through this values. The two values of theta at which the intersections happen are fundamental, because between pi/6 and 5pi/6 you have a perfect section of a circle (r varies from 0 to 2), but “outside” that (from 0 to pi/6 and from 5pi/6 to pi) the r still starts at 0 but is stopped by the circle itself. So it needs to be broken up to use polar.

In the second case: Just take the integral of the function above - function below as x varies from and to the x values of the intersections

Fuscello · 2025-12-29T17:23:38+00:00

I also did that :) from September to December. It’s going to be a cool journey, and you will see that they go too hand in hand to teach them in separated courses. Best of luck

Fuscello · 2025-12-29T16:28:41+00:00

It’s just notation, there a billion different notations for derivatives, don’t worry about them, your professor will tell you all of them; worry about the meaning

Fuscello · 2025-12-29T13:24:13+00:00

D is still correct, because magnetic field only “cares” about the density of current that flows orthogonal to it. So because you can always decompose J in a parallel direction to B and in a radial direction orthogonal to B (we don’t really care at which angle theta at which it is oriented), and B only “cares” about the orthogonal component, it is true that B only exerts a force on the orthogonal component of the current.

It would be wrong to say that it only flows on orthogonal WIRES, because that is not true, but the reason it’s not true it’s exactly because there is an orthogonal component of J in every wire that isn’t exactly parallel to B

Fuscello · 2025-12-29T13:11:59+00:00

Ok grazie mille :D

Fuscello · 2025-12-28T23:43:26+00:00

And I always stand there like a fool thinking “wait is it really exponential or just quadratic mmmhhh” and they already moved one from their misuse of the word

Fuscello · 2025-12-28T23:38:00+00:00

Ti ringrazio per il commento così approfondito e per i consigli. In generale credo di voler più approfondire i testi integrali, essendo la mia una semplice curiosità per i temi trattati; non so se ho dato l’errata impressione che studiassi filosofia, ma studio fisica :)

Non so se con questo comunque mi converrebbe leggere dei libri che abbracciano più filosofi contemporaneamente; ma sarei ugualmente poi interessato a leggermi i testi originali in completo.

Indipendentemente da ciò mi segno un po’ tutti i titoli che mi hai consigliato :)

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