Confusion Definition and 1000 Threads

Assume we have a diode . We connenct the negative terminal of the battery(anode) to the n type region and we connect the positive terminal of the battery to the p type region of the battery.The net force forces electrons to start flowing from the n type region to the p type region.As long as we...

1) I know that the binding energy is the energy that holds a nucleus together ( which equals to the mass defect E = mc2 ). But what does it mean when we are talking about binding energy of an electron ( eg. binding energy = -Z2R/n2 ? ). Some website saying that " binding energy = - ionization...

Hi, i am currently in class 10 and have a lot of interest in physics(mostly quantum ,particle and astrophysics) and want to pursue it further but climate change occurring vigorously around us worries me a lot .what should i do ? pursue physics or pursue a course like engineering which will help...

Dear all, I've been reading and got confused of the concept below have two questions question 1) For <ψ|HA|ψ> = <Hψ|A|ψ>, why does the Hamiltonian operator acting on the bra state and <ψ|AH|ψ> in this configuration it will act on the ket state? question 2) what does it mean for H|ψ> = |Hψ>...

Hello, I am an undergrad currently trying to understand General Relativity. I am reading Sean Carroll's Spacetime and Geometry and I understand the physics (to a certain degree) but I am having trouble understanding the notation used as well as the ideas for tensors, dual vectors and the...

Hey there! I've recently been looking at calculating amplitudes, densities of states and scattering cross sections in QFT, but am having a little bit of trouble with the exact form of the cross section - particularly with factors of ##2E## for the energies of the incoming and outgoing particles...

The answer says B, it does makes sense, but why D is regarded as incorrect. If the Elastic Potential energy when loading is the area under the loading curve, so why not with the unloading?

I understand that waves are function of space and time in nature, so E(x,t) will be fundamental description of a wave. I notice that often people denote a wave as E(t) for instance, an envelop function of a pulse. For this case, E is an oscillation at a fixed spatial point x? So that the point x...

On page 59 of Peskin & Schroeder, there's a section on the lorentz transformation of field operators which I've attached. I'm confused about the part towards the end where he does a change of variable on the integration measure; it seems like he's only rewriting the lorentz-invariant integration...

In Lee Smolins book Time Reborn he discusses simultaneous events and says events that are far from each other we find that there is no absolute ordering that all observers can agree on. For some observers the two events may be simultaneous for other observers one event may be in the past of the...

Okay, so I did an elastic collision with Vernier carts and magnets. The results seem pretty good. Cart one started with -0.1205 kg*m/s ended with +0.1027 kg*m/s Cart two started with +0.1174 kg*m/s ended with -0.1118 kg*m/s So Total before = -0.0031 kg m/s and total after = -0.0091 kg m/s. If...

(I am not a physicist - so, please be gentle :redface:) I was watching a program last night on the SCI channel, Did the Big Bang Really Happen? and they were describing the 'Singularity' as being this super hot very dense and infinitely small thing. And then when it went through the 'inflation'...

So I was taught in school that heated low density gases produce spectral lines and cool low density gases absorb their spectral lines. I mentioned this to my husband and he asked me what the definition of hot and cool were and I had no idea. The more I thought about it, the more confused I...

From the FLRW metric Proper distance can be derived like this, $$ds^2=-c^2dt^2+a^2(t)[dr^2+S_k(r)^2d\Omega^2]$$ Let us fixed the time at ##t=t_0## for the measurement and assume that the object has only radial component, then the metric equation turns out to be, $$ds^2=a^2(t_0)dr^2$$...

From my interpretation of this problem (image attached), the force applied to the point charge is equal and opposite to the repulsive Coulomb force that that point charge is experiencing due to the presence of the other point charge so that the point charge may be moved at a constant velocity. I...

So let us say that there are 3 separate alien species that somehow speak and write the same language. Let us say that 2 of these have always lived and died in their spaceships/asteriod ... going at speeds close to that of light. Alien species 3. A3 leaves behind a message saying that at time t0...

In Einstein summation convention, the summation occurs for upper indices and its repeated but lower indices. However I have some confusion 1) $${\displaystyle v=v^{i}e_{i}={\begin{bmatrix}e_{1}&e_{2}&\cdots &e_{n}\end{bmatrix}}{\begin{bmatrix}v^{1}\\v^{2}\\\vdots \\v^{n}\end{bmatrix}},\ \qquad...

When a question only asks for the moment of inertia (of say, a T-section), do I have to find the moment of inertia with respect to both the x and the y axis?

Homework Statement 2. Homework Equations [/B] So I basically have to establish the non linear differential equation that governs the movement of this robot (relates d and theta): The Attempt at a Solution So I know that we should have the sum of torques equal to...

Using that ##\hat{a} =a = \sqrt{\frac{mw}{2 \hbar}} \hat{x} +\frac{i}{\sqrt{2mw \hbar}} \hat{p}## and ## a \dagger = \sqrt{\frac{mw}{2 \hbar}} \hat{x} -\frac{i}{\sqrt{2mw \hbar}} \hat{p}## We can solve for x in term of the lowering and raising operator. Now, recently I read a derivation of...

The left circuit is a simple live&neutral circuit, it is neutral (0V), because it is in fact 'grounded'. If I unplug the wire connection to the ground, makes both wire, live. Now, If I replace the grounding connection with a person, why would he receive the shock, doesn't the man 'neutralize'...

I have a question which asks me if an object with a mass of 2250kg starts from rest at the top of a frictionless ramp 10m long and is at an angle of 10 degrees horizontally, what is the velocity of the object the moment it reaches the bottom of the ramp? I have been trying to work out this...

I'm having a bit of an issue wrapping my head around the adjoint representation in group theory. I thought I understood the principle but I've got a practice problem which I can't even really begin to attempt. The question is this: My understanding of this question is that, given a...

Homework Statement So I'm really confused with mutual inductors and dot convention. If your answer is going to be a link to any website I can assure you I read them all and that only left me more confused. So here are my questions: Homework Equations 3. The Attempt at a Solution [/B] ->...

Homework Statement I'm working through an example with motional EMF and I'm having trouble understanding the directions of vectors so that I can apply induction law. The magnetic circuit seems complex because the circuit is used to analyze other situations but the air gap 3, the coil 3 and the...

I see a lot of ambiguous explanations of degrees of freedom on the web and I need clarification. Suppose there is an object in space that can move freely along either the x,y, or z axis. Do we say it has six degrees of freedom because it can move along the x-axis one way or the opposite way...

So I am very, very new to logic based questions, and in the past have solved some with relative ease but whilest scrolling through the next to find some example stuff I came across a website that gives a question and hints to the question if stuck, so I thought this would be good practice. But...

Hey there, If body 1, mass M1 has escape velocity V_e1 = (2GM1/r)**.5 but M2 is more massive than M1 is this relation still valid? In this case, the subordinate body really isn't the subordinate body so does this still hold? And r (distance b/t the two) changes not only due to the motion of M2...

I learned that there are two different definitions for the coefficient of restitution: e = final relative velocity / initial relative velocity and e = √(final KE/initial KE). However, I don't understand how these two definitions will always give the same value. If one particle with mass m...

Ok, I'm a bit confused with the spectrum of the Sun. Is the spectrum of the Sun continuous or absorption? Better yet, is it both? Or am I totally confusing myself? I understand that the source itself is continuous but it is partially absorbed (wrong phrasing?) as it passes through the outer...

I'm getting ready for the exam that's coming up and I just took the 2017 practice exam to see what the last gaps are that I need to fill. Question 96 of this exam asks: "The magnetic field inside a long coil of wire (solenoid) has a certain magnitude and direction when the coil is air filled...

If the radius unit vector is giving us some direction in spherical coordinates, why do we need the angle vectors or vice versa?

Homework Statement ok this is not a homework but i am confused by the derivation of ## f = \nabla (m . B)## both start out with ##\vec B(r) \approx \vec B_0 + (\vec r' . \nabla)\vec B|_0 ... \\ f = \iiint_{v'} \vec J( r') \times (\vec r' . \nabla)\vec B|_0 ## where prime is body coordinates and...

Homework Statement Homework EquationsThe Attempt at a Solution My first attempt was to figure out what region the PMOS is operating in so that I could decide what equation to use - so I tried to find Vgs. Vgs = Vg - Vs. Vs is of course just Vdd but for Vg I did a KVL loop as below: My...

When an ideal gas,in a piston kind of system and whose equilibrium state is mentioned, is allowed to expand (piston is allowed to move and not gas leaking )against a constant external pressure very quickly, then, is the work done by gas zero or not zero ? The argument for work being zero is...

hi is theta used in degree or radians in Scherrer's equation..

I think the title sums up pretty well my doubts. I learned QFT from Peskin and Schroeder and other common sources, all implicitly defined QFT at zero temperature. Then I started learning about lattice QCD, how to define the action, how to find continuum limits, the importance of the dependence...

Homework Statement Hello to everyone who's reading. :) I hope I posted this in the right place; while this is not exactly a homework problem, I am trying to improve my understanding of the background information before proceeding with course-style problems. This post is because I'm trying to...

i have heard how our broadcasts will be seen by aliens far away or whatever. but i realize those signals are going to "attenuate" by d^-2 anyway... how come in astronomy we can see light sources millions of light years away? shouldn't those signals be far too weak to detect after such a long...

The question is simply posed as " identity the variables as discrete or continuous. 1) Mark of a student in an examination. 2) Family income." What I think: 1) There must be a minimum gap between two possible consecutive marks that the examiner can assign. Eg. Suppose that there are N students...

By Clausius' inequality δq - TdS ≤ 0. For a constant T,P process in a closed system and no non-expansion work my text states that dG = dH - TdS = δq - TdS ≤ 0 but this seems incorrect to me. If pressure is constant such that dH = δq, doesn't this mean that δq = δqrev since dH is a state function...

I find my self quite confused about some aspects of the concept of entropy. I will try to explain my confusion using a sequence of examples. All of the references I cite are from Wikipedia. Ex 1. Does the following isolated system have a calculable value for its entropy? Assume a spherical...

Hello experts, Full disclosure: I am a total layman at math, nothing in my training aside from high school courses and one college calculus class. I'm sure a week doesn't pass without someone posting a question about or challenge to Cantor. I am not here to challenge anything but rather to...

Anyone know if the following statement is true (and why)? "Getting to higher ground would increase his gravitational potential energy, decreasing the effects of non-conservative forces, which would allow him to move easier." CLARIFICATION: "move easier" refers to a lack of friction and not the...

Dear All, I've been recently reading the very clear text of Burns and Glazer entitled Space Groups for Solid State Scientists in the context of my thesis which requires understanding of symmetries of crystals, more specifically symmetries of (approximate triply periodic minimal surfaces)...

I’ve just realized something is wrong with my understanding of SR and I would really appreciate if you helped me sort it out. :) This won’t be a post with loads of formulas, rather the confusion is a conceptual. One way to describe my confusion is to put it into the twin paradox, although it’s...

In Peskin's textbook chapter 7 Radiative Corrections: Some formal developments (page 229), he said the Z factors are irrelevant for calculations at the leading order of perturbation theory, but are important in the calculation or higher-order corrections. My question is how can the Z factor be...

So, I know that enzymes are not consumed in the reactions they catalyze, and that they catalyze these reactions by lowering the activation energy. So, in an uncatalyzed reaction, more energy is required to "kick off" the reaction, resulting in the same overall change in free energy. I'm just...

i have used series solutions to differential equations many times but i never really stopped to think why it works i understand that the series solution approximates the solution at a local provided there is no singularity in which frobenius is used but i am not understanding how exactly it...

We can find the force by finding the E-field on the charge first, then applying Lorentz force formula. However, it isn't obvious to me at all how to find the E-field. If the charge were on top of the hemisphere I would be using spherical coordinates, but here I don't know which coordinate system...