Physical Definition and 1000 Threads

Go easy on me please as I am just delving into the world of physics and the likes :D I may have this completely misunderstood, so bear with me and correct me where I'm wrong please. There are 2 types of currents, DC and AC. Correct? AC stands for Alternating Current and DC stands for Direct...

I am a beginner in quantum mechanics. I started out with D. J. Griffiths' book in quantum mechanics. I'm having a problem in understanding the wave function. What is the physical meaning of the wave function? I searched on the net but didn't get any good explanation. I understand that the...

Hey guys, I am having issues with understanding the physical nature of pure and mixed states. Maybe you can help me out? 1) A pure state - superposition is a state that consists of different states at the same time. It's like having several waves, each one belonging to an Eigenstate of the...

I am trying to connect a second pair of speakers to my amp without the use of wires. It is really only one speaker position where running wires is impractical.

An example of how trying to teach someone exposes gaps in your knowledge: I was talking to someone about why we have line, neutral and Earth conductors. We got on to the fact that the Earth is an enormous sink and source of charge, so anything referenced to it can be considered 0 volts. Then...

I read that : An electric potential (also called the electric field potential or the electrostatic potential) is the amount of work needed to move a unit positive charge from a reference point to a specific point inside the field without producing any acceleration. Typically, the reference point...

The electromagnetic wave equation being of the same form in all intertial frames is because Newton's force is a vector quantity? I mean, if the wave equation changes its form from a intertial frame to another one, would the electromagnetic force be different in the two frames? I know that one...

There's a question that's been in my mind for quite a while but I cannot figure out what the answer is. I't probably an ill posed question but I will ask it anyway: 1.- Do we know what the dark-matter statistical distribution in our Universe is (at large scales)? 2.- In case we do, could...

Homework Statement Yesterday, our physics class had a laboratory examination, in which we used a protractor as a "weight". We hung some paperclips and checked the angle. Then, they asked about the physical meaning of the slope of the graph: tan( angle) as a function of n( number of...

I'm trying to understand the physical details of the mechanism, by which galvanic cells work, instead of more abstract descriptions of the half reactions that take place and I find it hard to piece together concrete information on this. Below is a description of my basic understanding of the...

I'm studying the motion of a physical pendulum, could someone help me make the final step in figuring out how to find the period so I can make predictions before carrying out a practical? Basically I have a meter rule with holes drilled along the length and will be pivoting it at various points...

As I understand it, the classical source-free electric, ##\mathbf{E}## and magnetic, ##\mathbf{B}## wave equations are solved by solutions for the electric and magnetic fields of the following form: $$\mathbf{E}=\mathbf{E}_{0}e^{i (\mathbf{k}\cdot\mathbf{x}-\omega t)}$$...

What does it mean for the laws of physics to be reversible in time? Does it mean that for every possible physical process, the same process can happen as it would do if we "played the tape backwards" so to speak? If a particle follows a path due to some physical law, Does it mean that if we were...

Classical physics is a nonlinear theory, but how is it that? Why is it nonlinear? Also quantum mechanics is a linear theory so that the sum of the solutions of the schrödinger equation is itself a solution. But I'm not sure I grasp this completely. Why is quantum mechanics linear while...

Within the context of the de Broglie-Bohm pilot-wave theory, can anyone explain what the pilot wave is in physical terms? I’m having a hard time understanding how, for example, the pilot wave influences the trajectory of a photon in the double-slit experiment. Are we dealing with...

Homework Statement I have recently come across the notation <ψ|Φ> in my notes and am not quite sure what it means. Some articles I have read online state that this is analogous to the dot product, except that this is the "dot-product" of 2 wave-functions. Would I then be right in saying that...

Given a massive particle traveling freely. Also assume that it is in a momentum eigenstate - a pure unmodulated sine wave in position space. In non-relativistic quantum mechanics, the phase velocity for that particle would be greater than the velocity of light. Does the phase velocity for...

##\frac{dp}{dt}## is given the name 'force' but ##\frac{dp}{ds}## has no name. I know 'force' is useful for calculations and predicting the future of the system. If 'convenience in calculations' is the reason why some quantities are given names, then I don't see why ##\frac{dp}{ds}## doesn't...

I have read some paper about transport measurement of graphene. From classical hall effect, we can get some information about kind of charge carrier, charge density etc. So, it is important for understanding matter. But, I don`t know why quantum hall effect is important in graphene transport...

Hello. I have studied about DWBA (distorted wave born approximation). But, I do not know the physical meaning of "DWBA without spin-orbit interaction". I think, I can not understand about meaning of spin-orbit. How can I understand "without spin-orbit intertaction". Thanks.

< Mentor Note -- thread moved to the EE forum from the Homework forums since it is a more general set of questions >[/color] So, we are going into Kirchhoff's Laws in class, and my entire understanding of circuits, which took me a while to form, is again falling apart. A physical understanding...

I'm currently working through Robert Klauber's Student Friendly Quantum Field Theory, which by the way is much more accessible than other texts like, say, Peskin and Schroeder, for others also coming into QFT via the self-study path. Anyhow, he mentioned something that never really clicked...

Admins: Please excuse my E and brackets in the title, and correct if possible. My questions are these, please: 1. What is the physical significance of (\hat{a}\cdot\boldsymbol{\sigma}_{1}) in \left\langle...

Is it true that one straight line goes through only 2 points?? If no then how ?? If yes then why??

Are the physical properties of a particle spread out through the wave function in bohmian mechanics? This is from wikipedia "Also, unlike in classical mechanics, physical properties (e.g., mass, charge) are spread out over the wavefunction in de Broglie–Bohm theory, not localized at the position...

Homework Statement Hydrogen peroxide can be prepared in several ways. One method is the reaction between hydrogen and oxygen, another method is the reaction between water and oxygen. Given the ΔG°rxn values for each reaction, which method (reaction 1 or 2) requires less energy under standard...

We all know that there's plenty of evidence showing that exercise does benefit cognition. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3951958/ The real question is how can I actually use this in practice to get real world results. So if I spend 8 hours a day studying a certain subject/trade...

Can we say that TIME is essentially the progression of energy from one state to another, in its long cosmic quest to achieve equilibrium? Without the movement of electromagnetic waves and transfer of energy, the entire universe would come to a standstill — an inanimate, “frozen” world. Time...

Bell (1964) http://cds.cern.ch/record/111654/files/vol1p195-200_001.pdf has 3 unnumbered equations following his equation (14). Let them be (14a)-(14c). Bell then uses his equation (1) to move from (14a)-(14b). It seems to me that he uses this: [A(b,λ)]2 = 1. (X)...

I am looking for resources on the physical properties of the various components that make up the human body. As an example of what I am looking for; If we look at the finger, we know it has bones, skins, nails, blood etc. What are the various physical properties of these different parts...

I want to model atoms of the periodic table using OpenGL (API for 3D graphics). I was told by a physics teacher one time that this cannot be done because it's not solvable. Can you guys confirm? Apparently only the shells of the hydrogen atom has been solved meaning that I can only model the...

In addition to being intelligent and possessing important skills, are there any specific height and weight requirements for Mars astronauts? For example, a neighbor on my street would like to become an astronaut. However, he weighs approximately 300 pounds.

Homework Statement Calculate Work(w) when 6.5L of an ideal gas at an initial pressure of 34.3atm is expanded or compressed isothermally to a final volume of 34.3L reversibly. Answer in J Homework Equations PV=nRT P1V1=P2V2 w=-nRT In(V2/V1) The Attempt at a Solution Using w=-nRT In(V2/V1) I'm...

Homework Statement The energy operator for a time-dependent system is iħ d/dt. A possible eigenfunction for the system is Ψ(x,y,z,t)=ψ(x,y,z)e-2πiEt/h Show that the probability density is independent of time Homework Equations ĤΨn(x) = EnΨn The Attempt at a Solution [/B] I understand the...

Posting as this was buried in another thread - If Lorentz invariance is broken in, e.g., whatever theory of quantum gravity turns out to be correct, what effect would this have (if one can speculate) on the physical vacuum? That is, for two observers, let's say, moving at different, constant...

I understand the definition of continuity on a manifold based on open sets. I was questionning myself about what is the corresponding physical meaning of an open set of a manifold (M, Power-set-of-M, Atlas). Is it a simple (maybe simplest) assumption in order to define mathematically continuity...

Photon energy E_p= hv=hc/lamda taking lamda= h/mc which is the electron Compton wavelength and substituting in above E_p=mc^2 L(angular momentum)=r X P=(Lamda/2)*(E_p/c)=h/2 are these results coincident or have any physical meaning, they relate a photon wavelength equal to an electron...

Just googled, "Is the universe infinite?" and got this: "The surface of the torus is spatially flat, like the piece of paper, but finite. However, with expansion, it is possible that even if the universe just has a very large volume now, it will reach infinite volume in the infinite future."...

The principle of minimum total potential energy is frequently used in solid mechanics as an elegant way of deriving the equilibrium equations for an elastic body under conservative forces. This method states that out of all the possible displacement fields that fulfill the boundary conditions...

I cannot conceive of time as an actual physical existence. What are the current opinions on what time is?

If you Increase or decrease temperature and change states of matter, that's a physical change. But are there any circumstances where temperature can cause a chemical change? Like if increasing temperature could break the bonds between the atoms and separate them? And I don't mean a combustion...

Hi, II have an issue with nodes in QM, like suppose in a well, the number of nodes depend on (n-1), the thing is that, what is so special(physically) about the point that the particle cannot be located there? Thanks is advance

I have had some issues understanding this topic. On two occasions Dale has pointed out to me that they are not really based on physical things, given that their values are completely arbitrarily defined for the purpose of matching certain measurable or defined things, like the ampere and the...

##P^{\mu}## generates translations and extracts the four-momentum of a particle when it acts on the momentum eigenstate of a particle. ##J^{\mu\nu}## generates rotations and measures the spin angular momentum along the ##i##-direction of a particle when it acts on the ##i##-th direction spin...

Really odd question for you guys but I'm curious about your input, and apologies if it's a foolish question to ask anyway(I'm a CS student and this came up in a discussion with a classmate of mine). So I know this is a fairly odd thought and not likely practical in any real world scenario, but...

Hello, A professor once told me that light can really do it. Is anyone knows about the phenomenon , and can explain me about it?

I've been reading this recent review paper by Senovilla & Garfinkle on The 1965 Penrose singularity theorem. In sect 8.3 (p38): Their eqn(6) is on p8: ##R_{\rho\nu} u^\rho u^\nu ~\ge~ 0 ~.## The message I take away from this is that much of the theory about singularity theorems has turned out...

I know that taking the derivative of certain functions that explain physical phenomena can lead to another statement describing the physical system, the most famous being the derivatives of position. That is, position-->velocity-->acceleration-->jerk-->jounce...and taking any other further...

Hi. I have a question about Organic and Physical Chemistry. I have already finished General Chemistry I and II and got decent scores on both of them (B on both of them). I am interested in taking Organic Chemistry, then Physical Chemistry afterwards. I know that both are different from General...

Schrodinger Equation is the very first step when we start learning QM. However, I never learned about the physical meaning of it. I have read a number of articles and discussion online. Regarding the ones I understand, there are generally two points of view. 1. Fundamental physical laws are not...