Potentials Definition and 244 Threads

The Attempt at a Solution I think I may of been too general with the volume in finding M_0 I'm assuming r_0 = r_M although I'm not sure why different notation is used thougj http://imageshack.us/photo/my-images/3/gravscan.jpg/

Homework Statement Not sure if this is a homework question but figured this is the best place to put it. When I touch something, how is the stimulus turned into an action potential? how does the body convert the energy of the stimulus into energy that can be used to modify an electrochemical...

Plz help me out with this difficulty. Here is a figure showing two conducting spheres(haven't drawn all EF lines):- Here is the problem, Suppose one of the spheres is charged with a charge +Q, other is neutral , so charges will get induced as shown in figure. The left portion of orange...

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...

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.

Hi, I am a mathematician, and recently got interested in the problem of compression of multi-dimensional functions. Particularly, there is a large piece of theory developed for fast computations with Newton potential \frac{1}{\|x-y\|}, where x, y \in R^{d}, d\geq 3. Is there any interest...

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 Calculate the membrane potential (Vm) of a cell, given the following resistances and equilibrium potentials (10 marks) E(K) = -80mV, R(K) = 0.2*10^6 ohms, E(Na) = 60mV, R(Na) = 0.2*10^6 ohmsHomework Equations Not sure The Attempt at a Solution In my texts I have read...

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...

Homework Statement hey I am having trouble figuring this out. The question states that i am to find the second component of velocity? there is a plane wave incident on a surface at (0,0). Homework Equations the incident potential is \Psi^{I} (x,t)= A\, e^{-i\omega (t-...

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...

Homework Statement Which of the following statements is correct if Standard reduction potentials of Cu and Sn are 0.337V and -0.136V resp. (both from +2 charge) a) Cu2+ ions can be reduced by H2(g) b) Cu can be oxidised by H+ c) Sn2+ ions can be oxidised by H2(g) d) Cu can reduce Sn2+...

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...

Selecting retarded potentials as solutions of the Maxwell's equations or of more generally the electrodynamic equations implies selecting one arrow of time. It is normal to assume that this arrow of time is consistent with the thermodynamic arrow of time implied by the second principle of...

Homework Statement Calculate and sketch the effective potentials V (r) for the radial motion of particles, for the cases of massive and massless particles. Interpret this effective potential: are there stable orbits? Are particles attracted to r = 0? Can particles reach r = 0? Homework...

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...

Homework Statement For Cyclohexane Boiling point T_b = 80.1°C P = 1atm \Delta H_{vap} = 30.1 kJ/mol Determine at phase change liquid to vapour, Changes in: a)Entropy per mole b)Gibbs free energy per mole c)Internal energy per mole assume ideal gas behaviour for the vapour...

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...

Consider a thin spherical shell of radius a and mass per unit area \sigma whose centre at O lies a distance r from an external point P. If the gravitational potential r is \Phi(r), verify that the external potential due to the shell will be equal to that due to a point of the same mass as the...

\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...