Potentials Definition and 228 Threads

Homework Statement I want to prove that coefficients of potential are non-negative. i.e. Pij ≥ 0 Homework Equations By coefficients of potential method we know that in a system of conductors the potential on ith conductor is related to charges on conductors by: \Phii = \sum Pij Qj...

Hello. I've been reading an interesting article by a pair of smart fellows... http://rmp.aps.org/pdf/RMP/v21/i3/p425_1 J. A. Wheeler, R. P. Feynman. "Classical Electrodynamics in Terms of Direct Interparticle Action". Reviews of Modern Physics. Volume 21. Number 3. 1949. I haven't...

Hello! This has been driving me crazy for aaaaaaaaaaaaaaaaaaaaaaaaaaaages. It's about equilibirum potential. Okay, say I have a cell with High K+ concentration inside and low K+ concentration outside, and the opposite for Na+. If for each cation there is an anion, then the voltage across the...

[FONT="Times New Roman"]I read from a book that the "total energy is not preserved when the potential depends explicitly on time", i.e. U(x,t). Can anyone show or prove it? Many thanks.

Homework Statement Consider an infinitely long and thin line of charge, with density 8nC/m. Calculate the electric potential difference ((phi)1-2) between two points in air at radial disances 1mm and 3mm.Homework Equations I am assuming: Phi(r) = λ/2(pi)ε0 * ln(rR/r) where rR is a reference...

Homework Statement While the voltage induced between the points P and Q is changing, which is the high potential end of the inductor? Explain your answer. P.S. sorry for the fail Paint job lol Homework Equations The Attempt at a Solution I know that in a DC circuit current flows from the...

Dear Everyone, I have a question about the separation of variables for non-central potentials (r, \theta, \phi). In spherical coordinates, such a potential V(r,\theta)=u(r)+f(\theta)/r^2 can be separated. Who knows it could also be separated in other coordinates? Many thanks.

Homework Statement The problem involves a particle confined to an interval 0 < x < L (in one dimension). It asks to solve for the functional form of the potential V(x) given a wave function (to get to the relevant question, I won't bother providing this). In order to solve for the potential, it...

Hello. I have been asked if it is correct to say that the force of a spring is conservative. So, for a mass attached to a spring on the roof it's OK. Now consider two masses linked by a spring. Now the potential will depend on both coordinates. It is now not so clear to me any of the...

Are there any equations for these? I have seen in books for the vacuum case but not for a dispersive media.

Homework Statement im manipulating the schrodinger equation for a central potential. at some point I need 1/r2 d/dr (r2 dR/dr ) to equal X''/r where R = X/r when i sub in R i get 1/r ( - dX/dr -1/r2 X'' +1/r X'' ) I'm most likely making an obvious error but nevertheless...

Ok so we've been given a problem to solve where: I(t) = q_{0} \delta (t) Find A(t,x) = \int^{ \infty }_{- \infty } \dfrac{ I(t_{ret}, z')}{| x - x'|} dz' All that I want is a hind because it was shown for the case that: I(t) = \left\{\begin{array}{cc} 0 , t \le 0 \\ I_{0} , t > 0

Homework Statement 1. Explain the term thermodynamic potential. 2. Explain the motivations for defining the enthalpy, the Helmholtz free energy and the Gibbs free energy. 3. The Helmholtz and the Gibbs free energy are measures of the distance to thermodynamic equilibrium. Explain...

Homework Statement Find the current I and potential V for a simple diode circuit from the picture using a) ideal diode model b) CVD diode model (Vd=0,6 V) [PLAIN]http://pokit.etf.ba/get/36406f902c2c24bd8a3c4ffa8fe97b78.jpg Homework Equations U=RI I1+I2=I The Attempt at a Solution This diode...

Homework Statement A cavity is made inside a solid conducting sphere and a charge q is placed inside the cavity at the centre. A charge q1 is placed outside the sphere as shown in the figure. Point A is inside the sphere and point B is inside the cavity. Find potential at A and B...

Homework Statement We have built a circuit with an ac source containing a resistor in series with a parallel RC combination, we have measured the voltage across the first resistor and the voltage across the RC combination with a high and a low frequency. 80Hz: V0 = 2,325 V en Vm = 2,780 V...

In quantum mechanics, we rarely talk in terms of forces and acceleration. Instead, we work with potentials and energy, and we restrict ourselves to conservative systems where the energy is constant. Why? There are several alternative formulations of classical mechanics, all of which are...

Can anyone please explain the concepts of scalar and vector potential and how they can be used to derive the wave equation for light? References are welcome. Thanks in advance for any help!

Just started revision for Quantum Mechanics after a very long break so everything is a bit rusty. Don't have anyone nearby at hand to ask, so hoping someone here will help. Been given Newton's second law of motion as F= m d^2 x/ dt^2 which is a second order equation hence requiring two...

Homework Statement A point charge +Q is surrounded by a spherical shell of inner radius a and outer radius b. The spherical shell has charge density \alphar. a) What is the electric field for r < a? b) What is the electric field for a < r < b? c) What is the electric field for r > b? d)...

Could someone tell me why the potentials are the same in http://i.imgur.com/EdnqE.jpg. I am talking about right under the part where it says "Also, the potentials across them are now the same, so that V = q/C gives". I understand everything prior to that. I even understand the stuff after it...

Homework Statement Evaluate the equilibrium constant for the formation of triodide ion. I2 + I- ------> I3- a 298K, if EI2|I-o = 0.6197V and EI3-|I-o=0.5355V I don't understand one thing - At equilibrium, ΔG=0 so that Eocell=0 (from the equation ΔG=-nfE) but Eocell is not zero for...

Generally the working fluids in a power generating system is either water (steam) or air. This I imagine is because they are widely available fluids. The specific heats of these ranging from some 1 - 2 kJ/kg-K. For the sake of argument, let's assume that hydrogen or xenon are equally...

Homework Statement The standard reduction potentials for Ni2+ and Sn2+ are as follows: Ni2+ + 2e− → Ni E° = −0.23 V Sn2+ + 2e− → Sn E° = −0.14 V Calculate the equilibrium constant at 25°C for the reaction Sn2+(aq) + Ni(s)→ Sn(s) + Ni2+(aq) Homework Equations Nernst...

Homework Statement A charged particle is moving at velocity \vec{v}=c\vec{\beta} along the z-axis. We're working in cylindrical co-ordinates. Here's a picture: [PLAIN]http://img696.imageshack.us/img696/9789/retardedpotential.png The problem is to get the Lienard-wiechert potential, which...

Hello, I'm learning how to solve Laplace's equation to find Potentials in Cartesian, Cylindrical, and Spherical Coordinates and let's just say it's not going as smoothly as I'd like. In particular, I'm having difficulty with the Spherical case which involves Legendre Polynomials, Method of...

Question on Solving Laplace Equation Potentials. Hello, I'm learning how to solve Laplace's equation to find Potentials in Cartesian, Cylindrical, and Spherical Coordinates and let's just say it's not going as smoothly as I'd like. In particular, I'm having difficulty with the Spherical case...

I am having some trouble interpreting different effective potentials The first potential is V = (L^2)/(2r^2) - (r^2)/(2R^2) - (L^2)/(R^2) The second potential is V = (-1/2) + (L^2)/(2r^2) -(L^2)/(R^2) What I am having a hard time identifying do these potentials have stable orbits...

Homework Statement A soap bubble 10cm in radius with a wall thickness of 3.3x10-6cm is charged to a 100V potential. The bubble bursts and falls as a spherical drop. Estimate the potential of the drop. Homework Equations V=kq/r U=qV -dV= E r=10cm a=3.3x10-6 The Attempt at...

Hi, I have a question that has been bothering me for a while now. For Kepler's problem we know that angular momentum M_{z} is conserved and that the angular velocity \frac{d\phi}{dt} is equal to \frac{M_{z}}{mr^{2}}. When we substitute for \frac{d\phi}{dt} in the expression for energy, we...

Hello, I have constructed a Faraday box containing electrodes that are going to detect the action potentials or/and local field potentials from inside the brain. I was wondering whether someone constructed something like this before and what strategies were used to reduce the noise...

\Delta\vec{A}-\frac{1}{c^2}\frac{\partial^2 \vec{A}}{\partial t^2}=-\mu_0\vec{j} \Delta\varphi-\frac{1}{c^2}\frac{\partial^2 \varphi}{\partial t^2}=-\frac{1}{\epsilon_0}\rho c=\frac{1}{\sqrt{\epsilon_0\mu_{0}}} \epsilon_0=8,85\cdot 10^{-12}\frac{F}{m} \mu_0=4\pi 10^{-7}T...

Hi everyone, I have a question related about the relation between potentials, connections and curvature in gauge theories. In Newtonian physics, the common starting point is Newton's law, which determines the motion in terms of the derivative of the potential, i.e. sth. like \ddot...

Hello all! I hope this question has not been raised previously, so that I wouldn't exhaust your time in vain, and if it had been, please forgive me, though extensive combing of the web yielded largely nothing. My problem concerns something extremely trivial: the derivation of the electric...

I have some questions about thermodynamic potentials (internal energy U, enthalpy H, Helmholz free energy F, Gibbs free energy G): 1. The differentials of potentials: dU<=TdS-pdV dH<=TdS+Vdp dF<=-SdT-pdV dH<=-SdT+Vdp Do this equations apply only for a single homogeneous system or can...

Homework Statement Specify at least two ( physical or chemical), real world, processes for each of this cases: a) Internal energy is constant b) Entalpy is constant c) Gibbs free energy is constant d) Helmholtz free energy is constantHomework Equations a) dU = TdS - pDV = 0 b) dH = TdS...

Homework Statement Write down expressions oer E and B fields in terms of \varphi and \bar{A}. Demonstrate that this definition of B is consistent with the non-existence of magnetic monopoles. Homework Equations The Attempt at a Solution The first part of the question is easy...

Hello guys, I don't know much about brain and stuff I only know a bit about action potential. My question is I can understand how sensory nerves by a stimulus, but let's say I want to pick a pen. How does brain initiate the action potential for that? This might have been dicussed before but...

I'm bit confused about this. This is my question This is the action potential duration of a normal cardiac myocyte [PLAIN]http://www.med.nus.edu.sg/paed/resources/cardiac_thumbnail/background/images/action_pot.gif Here are the potential pace makers. * SA node: 80 - 100 bpm * Atrial...

Is Fe2+(aq) capable of reducing Sn2+(aq) to Sn metal? The standard reduction potentials from my book are -0.14 for Sn2+ and -0.44 for Fe2+ Because Sn has a more positive Epot it has a greater tendency to be reduced. So add the Epot up: -0.14 + 0.44 (oxidation)= 0.3. It's positive...

Homework Statement A rectangle has sides of length 5cm (right and left) and 15cm (top and bottom). Top left corner has charge (q1) = -5uC Top right corner has charge A = ? Bottom left corner has charge B = ? Bottom right corner has charge (q2) = 2uC a) What are the electric...

What are the cell potentials of the following? 1) ZnSO4 (1M) & CuSO4 (1M) 2) ZnSO4 (1mM) & CuSO4 (1mM) 3) ZnSO4 (0.1M) & CuSO4 (1M) I tried using the nearst equation and I keep getting that they are all the same value of +1.10V

I suppose I could've equally well posted this to the math forum, but here goes... One often sees the two-body potential f(r1, r2) being reduced to to f(r12). Can this be done in a more general case (can n-body potentials be reduced to just the distances between all the particles, e.g. f(r1...

If we knew the four momentum of a neutrino should we then be in position to calculate whether the gravitational potential of our galaxy might "bind" that neutrino? Thank you for any thoughts.

Homework Statement Calculate the potential of a Zn^2+/Zn and Ag^1+/Ag couple. Homework Equations Zn^2+ + 2e^1– ⇌ Zn E= –0.76 V Ag^1+ + e^1– ⇌ Ag E= +0.80 V The Attempt at a Solution First I know to multiply the silver half reaction by...

I'm reading through the Introduction to Quantum Mechanics book by Griffiths (2nd edition) and it is describing delta-function potential wells. When it describes how to find bound states the energy is E < 0 (negative) in the region x < 0 (negative). It says the general solution is: \psi (x)...

A hollow spherical conductor of radius 3.00 cm has 6.00 nC of charge distributed uniformly over its surface. (a)What is the electric potential at the center of the sphere(in volts)? (b) If the conductor is solid rather than hollow, what is the potential at the center of the sphere? I know...

Does anyone know how either Lienard or Wiechert justified the (1-v/c) factor that appears in their potential formula for a moving charge?

I have a problem. I am trying to selfteach myself QM but I got stumped with this. Basically, in the issue of 1D step potentias, I know that you have to divide the problem into regions and solve the schrodinger equation for each one. However, when you solve it, you always get two solutions due...

I'm trying to find a divergenceless vector field based on its curl, and discovered that I could use a http://en.wikipedia.org/wiki/Helmholtz_decomposition" , and the article I found on this didn't make much sense to me. First, can someone confirm that the dimension referred to in the...