Self Definition and 584 Threads

If you were to have a fan, that has a button, that whenever you press it, the blades rotate (like those mini fans you can find at stores). But, when the blades rotate, they power electricity that powers the fan itself? Kind of like wind turbines but without the wind part.

Hi my name is Giovanni, I'm from Italy and I'm 26 years old. I apologize for my english which might sound incorrect or weird sometimes :oldshy: I loved physics and astronomy since I was a child. My father is an astrophysics graduate, we used to have long conversations about the universe and...

i am being told trying to make a self winding clock means ppm when this is a self winding clock https://en.wikipedia.org/wiki/Self_Winding_Clock_Company and this is a self winding watch https://en.wikipedia.org/wiki/Automatic_watch i hope someone speaks on my behalf to be allowed to...

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https://www.popularmechanics.com/science/a41106690/grandfather-paradox-time-travel/ I’ve been studying the self consistency principle, being the idea in time travel that history (the past) must be conserved. When I read about the grandfather paradox it sounded like the same thing. Are these two...

http://appliedscience.byethost7.com/index.php/Main_Page I dropped out of college and decided to self study.

I'd like someone to check that this solution is right, and if not, give me the point of failure and not the answer. Thanks!

I am teaching myself math and wondering if any of you have recommendations on trigonometry books for beginners and self study. Any help is appreciated!

Nearly two decades after I graduated with an engineering degree, I'm currently studying for a master's with a particular emphasis on conceptual/theoretical statistical physics. Based on my interests and stylistic preferences, I'm using the following books to build my understanding of physical...

Summary:: I want to teach myself physics and was wondering if Thomas' Calculus is a good book to learn the Calculus I need to learn introductory physics. Hi, I am following a guide by Susan Rigetti (https://www.susanrigetti.com/physics) which aims to help and give sort of structured learning...

I will be entering uni in less than a year, I will be pursuing a degree in computer science. I want to some day be able to understand "string theory" ,"quantum gravity" (as of now these are merely buzzwords to me) and understand the standard model in and out (so QFT, QED, QCD) even GR! So far...

Homework Statement:: n/a Relevant Equations:: n/a No More Calculus 1 Questions I came to the realization that trying to tackle two courses at the same time is simply not working out. I need to polish my algebra skills. I am not going back to Algebra 1 and 2. I am not going back to College...

Summary:: I want to study QFT 1 in the upcoming semester, so what are the prerequisites to study it. By QFT 1 I mean Classical field theory, Canonical Quantization, Feynman Diagrams, and QED. I am trying to self study QM from Griffiths' Introduction to Quantum Mechanics book. What are the sub...

Hi Pf I read that in the light propagator there are loops of electrons. What would be the consequences if we could switch them off (or neglect them)? would it modify the speed of the photons?

Hi PF, I hope y'all had a great Thanksgiving. Quick question, as I've mentioned before, I am non-traditional college student who is right at just over College Algebra/beginning Trig level in Math. While I am out of university, to make enough money to return, I am wanting to CLEP...

I want a suggestion on a book for learning HTML programming. You all know what my level is...which is NOT MUCH. I just want to get a book that is not too hard to learn. One that I can experiment and play with. Thanks

b) c and d): In c) I say that ##L_h## is only self adjoint if the imaginary part of h is 0, is this correct? e) Here I could only come up with eigenvalues when h is some constant say C, then C is an eigenvalue. But I' can't find two.Otherwise does b-d above look correct? Thanks in advance!

All intercontinental nuclear missiles have self destruct codes? This can work even when it's reaching the destination? But can the self destruct codes work even while the missiles are in silos so you could in principle detonate all nukes in the United States at the same time. Or do you have to...

Hi I'm doing a uni project and need help with a Self Excited AC Single Phase Generator. I'm using an AC Single Phase Induction Motor to act as the generator. Its turned by a DC Motor The AC motor is 1350 RPM and the DC motor is 2500 RPM Its not producing any electricity (just a few volts) for...

Hi everyone. I'll be taking a course in the fall called "Introduction to Mathematical Reasoning", which is basically and introduction to proof-based mathematics. The syllabus says we will be covering the first seven chapters of Smith, Eggen, and St. Andre's "Transition to Advanced...

Hello, so I am a 16 year old passionate about physics and mathematics, I’ve pretty much self taught myself everything. Before you start saying that I’ve got to focus on what I have, I am nailing everything science related, straight As, but I find them quite easy and I REALLY want to move on. I...

Hi, I am a physicist interested in going through a basic analysis course. The real line, open sets, that whole thing. On my own, so I need a good selection of bibliography, ranging from those that are good references but too dense to actually read to those that are very pedagogical but tend to...

This title says it all.

All in the summary, can't copy paste on phone :(

Hello all, Now I had graduated from high school, and I'd like to self-study (revisiting) high school mathematics and physics (not for exam). But recently I often saw ads for a local online course platform. Many of the platform's users have been admitted to top colleges, and get better score...

Hi all- I am trying to obtain eigenvalues for an equation that has a very simple second order linear differential operator L acting on function y - so it looks like : L[y(n)] = Lambda (n) * y(n) Where y(n) can be written as a sum of terms in powers of x up to x^n but I find L is non self...

Homework Statement: Hi, I am self-studying QM and was wondering if you could check to see if my answers are right to an online exam I took. There are no solutions availabel Homework Equations: See below A particle with mass m is in an infinite potential well of length x=0 to x=a Q1a. Show...

I am unsure whether this is the right forum to ask this question. This isn't a homework question but it has been troubling me for a while now. My university has replaced Electrostatics in our syllabus with Geophysics. So I am currently self-teaching Electrostatics using Griffith's Introduction...

I am currently teaching physics to myself, however when I start to comprehend one thing, an unknown term or equation finds me and I get stolen from my current reasearch to begin to research that. So my question is, where should I start? Is there any logical starting point to begin to teach...

Hello everybody! I have a big question about the renormalization: I do not understand why the "renormalization condition" is to impose the tree level result. Now I will explain it better. Let's take, for example, the electron self energy. The tree-level contribution is the simple fermionic...

Two coils are made of copper wires of same length .In the first coil number of turns is 3n and radius is r . In the second coil number of turns is n and radius is 3r the ratio of self inductances of the coil is: I know that self inductance of a solenoid is μN2A/l ; where A = area of cross...

I have a book called "Grokking Algorithms", and when I'm done with my current tabletop game project I plan to work through this as much as it seems worthwhile to do so. I was not at my best when I took the class that corresponds to what's in this book, so I figure it would be good to study it...

Hi all. I'm looking for a little guidance on starting out in self-studying analysis. The reason is two-fold. Firstly, I am very interested in it and want to have a deeper understanding of Calculus rather than the computational plug and chugs I learned in Calculus I last semester. Second, I've...

In my physics education, I shied away from heavily theoretical stuff like General Relativity. I took the required sequence in Quantum Mechanics but having never used it on the job, much of that knowledge has faded too. I started a course in Quantum Field Theory but dropped it. I had friends...

Homework Statement Prove Sturm-Liouville differential operator is self adjoint when subjected to Dirichlet, Neumann, or mixed boundary conditions. Homework Equations l = -(d/dx)[p(x)(d/dx)] + q(x) The Attempt at a Solution I have no idea. If someone can give me a place to start that would...

Hi, I have a general question. How do I show that an operator expressed in spherical coordinates is self adjoint ? e.g. suppose i have the operator i ∂/∂ϕ. If the operator was a function of x I know exactly what to do, just check <ψ|Qψ>=<Qψ|ψ> But what about dr, dphi and d theta

From his original thesis, Einstein said light speed is always constant (c). There is very clear evidence for this. Every ray of light moves in the “stationary coordinate system” with the same velocity c, the velocity being independent of the condition whether this ray of light is emitted by a...

Hello, I am a second year PhD student in mathematics currently studying logic. I have recently begun questioning staying in the field, and I really think I may want to work in Machine Learning, at the very least in the theory of it. I am willing to self study from machine learning books, but...

https://electronics.howstuffworks.com/everyday-tech/lithium-ion-battery2.htm "Lithium-ion batteries age. They only last two to three years, even if they are sitting on a shelf unused. So do not "avoid using" the battery with the thought that the battery pack will last five years." Is this...

Flash point temperature of petrol is lesser than that of diesel at the same pressure. Does this mean, if I take petrol and diesel as liquids in separate containers and heat them, rapid vapourisation (rapid enough to sustain a combustion) of petrol occurs at a lower temperature(fire point) than...

To self study the theoretical part of general physics is as "easy" as going through a textbook, but how could a person self study the experimental part of general physics at home? Any ideas? (Should be easier than to self study chemistry lab hahaha)

Is there any difference between setting petrol on fire directly(by contacting it with burning stick) and heating petrol in a vessel, increasing its temperature above itself ignition temperature and making it burn spontaneously? What is the difference between flash point,fire point and self...

Take a neutron star, its surface will be gravitationally self magnified so that it looks bigger to the distant observer, than it 'really' is, plus you can see some of the rear facing surface. If you take the centre of the neutron star, then this process must go on there also, although unseen...

Homework Statement Homework EquationsThe Attempt at a Solution Self inductance depends on the geometry of the solenoid . It doesn't depend on the sense of windings . So , L1 = L2 . But I don't understand how to deal with superconducting wires . Does a superconducting wire affect the...

Homework Statement Homework EquationsThe Attempt at a Solution Self inductance L = μ0n2πr2l . This means it depends only on geometrical factors . So , self inductance in both the cases should be equal . But if I think in terms of L = Φ/I , then Magnetic field at the center is twice that...

Greg Bernhardt submitted a new PF Insights post Ask the Advisors: What academic advice would you tell your 18 year old self? Continue reading the Original PF Insights Post.

I’m starting my undergraduate physics degree next semester but I really like to study different fields on my own without any external motivation or obligation related to school. As I want to be a theoretical physicist I think this is something that I really have to be good at, because I imagine...

Find Green's function of $$K(f(x)) = (1-x^2)f''(x)-2xf'(x)+\left(2-\frac{1}{1-x^2}\right)f(x):x\in[cos(\alpha),1]$$ subject to boundary conditions: $$f|_{x=1} < \infty\\ f|_{x=\cos(\alpha)} = 0.$$ Two fundamental solutions are associated Legendre polynomials (after all, this is Legendre's...

Has anyone been successful self studying mathematics and physics? By successful I mean to achieve your goals to study and have firm understanding in the subjects. How did you do it? How long did it take?

Hey guys, I have never finished algebra 1 in high school which was around 10 years ago. I want to start myself on a good foundation so I can learn more advanced math. My ultimate goal in the end is to learn meteorology; so I need to start somewhere. For algebra 1 are you able to list things...