Potentials Definition and 228 Threads

Hi All - Let's say I have a potential energy surface with two minima, one higher than the other. We will label the higher minima B and the lower minima A. Each potential well can be approximated as a harmonic potential with force constants kA and kB for wells A and B respectively. How small...

Homework Statement A uniform line charge of density pl = 1nC/m is arrange in the form of a square 6m on a side. (In the z plane) Find the potential at (0,0,5) m Answer:35.6 V Homework Equations R = The distance from the line to the point (0,0,5) dL = ax dx + ay dy + az dz The...

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Homework Statement Two capacitors of 2.0F and 5.0F are connected in series; the combination is connected to a 1.5 volt battery. What is the charge stored on each capacitor? What is the potential difference across each capacitor? Homework Equations C = Q / (Delta)V The Attempt at a...

Explain why cell potentials are not multiplied by the coefficients in the balanced redox equation. (Use the relationship between delta G and cell potential to do this.) i know that cell potential is an intensive property but i don't know how to explain why you don't multiply the the cell...

Homework Statement A long coaxial cable carries a volume charge density rho=alpha*s on the inner cylinder (radius a) and a uniform surface charge density on the outer cylindrical shell (radius b). This surface charge is negative and of just the right magnitude so that the cable as a whole is...

Homework Statement Consider the following arrangement of potentials and a test charge (not pictured) located at infinity. - To which location will a test charge of +3 microColumbs travel? The potentials are as follows: (-1V) top left (-7V) top right (+1V) lower left (+4v) lower...

Im doing some study on scalar and vector potentials in the area of electromagnetics, and the author of the book derived this equation \vec{E} = -j\omega\vec{A} - \nabla\phi where \vec{A} = vector potential and \phi = scalar potential and \vec{E} = time harmonic form of electric field...

Homework Statement A particle of mass m and E<V0 approaches from the left and encounters a potential barrier, assume the amplitude of the incoming particle is A. Write the time independent wavefunction for x>0 and x>0 at t=0 E is definite. Find the reflection coefficient of the particle...

Homework Statement There are a couple of introductory questions that aren't relevant to the last parts then it says: (d) If the current density is time independent and divergence free, show that the Maxwell Equations separate into independent equations for E and B. (e) Express E in...

Consider 3 charged spherical shells A, B, C with charges q_A, q_B, q_C and radii r_A<r_B<r_C V_A=\frac{1}{4\pi\epsilon}[\frac{q_A}{r_A}+\frac{q_B}{r_B}+\frac{q_C}{r_C}] V_B=\frac{1}{4\pi\epsilon}[\frac{q_A}{r_B}+\frac{q_B}{r_B}+\frac{q_C}{r_C}]...

Hello! I'm trying to grasp the "intuitive" meaning of the thermodynamical potetials E,F,H and G, or at least of their connections. As in other threads before mentioned, I learned that you can't real.y give an meaningful definition of energy , so I assume for the other potentials this is...

Starting from the equation dE=tdS-PdV+\mu dN It is straightforward to derive all 8 possible thermodynamic potentials. My question is the following: Why are the only important potentials Entropy Helmholtz free energy Enthalpy Gibbs free energy Grand potential ? Why aren't the other three as...

My electrodynamics lecturer was talking about how potentials are arbitrary and that's why we have different gauges. I'm not too sure about how potentials can be arbitrary. Up to a constant? How? Cheers,

Excuse me but, this is a rough translaton from a Portuguese homework. Also, excuse me for my lack of knowledge in some physics, I do a programming course and one of the teachers said we had to know about this. Homework Statement http://img181.imageshack.us/img181/7084/87202322av0.jpg...

Hi, Just having a little trouble understanding the concept of standard cell potential...what is it exactly? I understand that it is compared to a reference potential of 0 for the reaction 2H+ + 2e- -> H2(g). But what does it mean when a given reaction has positive potential (other than the fact...

Homework Statement Suggest why manganate(VII), rather than dichromate(VI) is used to titrate with Fe(II) in volumetric analysis. The Attempt at a Solution i have figured out 2 possible answers but both may not be correct... 1. the colour change is sharper with manganate (purple to...

Homework Statement The general gauge transformation in electrodynamics is {\bf A}' = {\bf A} + \nabla \lambda and \phi ' = \phi - {{\partial \lambda}\over{\partial t}}. In the Lorentz gauge, we set \nabla . {\bf A} + {{\partial \phi}\over{\partial t}} = 0 . My question is: Is the...

Hello: There is a well known theorem which asserts that every attractive 1D potential has at least one bound state; in addition, this theorem does not hold for the 2D or 3D cases. I've been looking for a proof in my textbooks on qm but I've been unable to find it. Can you help me out? Thanks!

I can appreciate the degeneracy of an infinite cubical well, in which there are three different directions, and hence three different separation constants from Schrodinger's equation which determine three separate n's (for lack of a better word.. principal quantum numbers, i suppose. it really...

hello, I've just gone through a derivation using the vector potential A, and using the equation derived (a wave equation) which arises from using the lorentz gauge, it is applied to the problem of a current sheet in the xy plane, located at z=0 with current in the x direction only. the current...

Hey... I have a quick question for you guys about electric potential. I have a spherical shell with a constant charge distribution. The total charge(Q), along with the shell's radius is given. Also, V(infinity) is defined to be 0 in this case. I'm told to find: a. The potential at r = the...

Homework Statement Griffith's problem 10.8 Show that retarded potentials satisfy the Lorentz condition. Hint proceed as follows a) Show that \nabla\cdot\left(\frac{J}{R}\right)=\frac{1}{R}\left(\nabla\cdot\vec{J}\right)+\frac{1}{R}\left(\nabla '\cdot\vec{J}\right)-\nabla...

I'm kind of confused as to how to determine when a vector field is conservative. For example, if we consider the following scalar field: \varphi = arctan(\frac{y}{x}) We see that the gradient is: F = \nabla\varphi = \frac{-y i + x j}{x^{2} + y^{2}} However, F is not a conservative...

Homework Statement 3 equal point charges, each with charge 1.55 microColoumb, are placed at the vertices of an equilateral triangle whose sides are of length 0.100 m. What is the electric potential energy of the system? (Take as zero the potential energy of the three charges when they are...

Homework Statement There is a +1 micro-coulomb charge at the origin and a -3 micro-coulomb charge at 2 meters away along the x-axis. I am suppose to find the change in Voltage if second charge is moved to 4 meters away from the origin. Homework Equations I am thinking of using delta V=...

Homework Statement Hi all. Please take a look at: http://books.google.com/books?id=9p6sUTxUoZ0C&pg=PA417&lpg=PA417&dq=%22seek+a+vector+potential+that+is+parallel&source=web&ots=peoLUp4z_M&sig=vaRVDMazSj10x0k4v4iGKCHni0o What do they mean by that hint? The Attempt at a Solution...

Homework Statement In its resting state, the membrane surrounding a neuron is permeable to potassium ions but not permeable to sodium ions. Thus, positive K ions can flow through the membrane in an attempt to equalize K concentration, but Na ions cannot. This leads to an excess of Na ions...

Hi, Can anyone help me to understand the following please? If a potential is symmetric does this mean that the eigenstates are either symmetric or antisymmetric? Is the ground state always symmetric and the first excited state always antisymmetric? Thanks!

If I have some arbitrary Thermodynamic system, and I want to find the equilibrium state what do I do? Lets say that I know Internal energy: U(S,V) Helmholtz free energy: F(T,V) Enthalpy: H(S,P) Gibbs free energy: G(T,P) (I omitted the dependence on particles N) I've been...

yes ------Is Ni2+(aq) capable of oxidizing H2(g)? no -------Is Fe2+(aq) capable of reducing VO2+(aq)? no -------Is Cr3+(aq) capable of oxidizing Fe2+(aq) to Fe3+(aq)? yes ------Is Sn2+(aq) capable of oxidizing Fe2+(aq)? yes ------Is Fe3+(aq) capable of oxidizing Sn metal to Sn2+(aq)...

Homework Statement The first ionization potential of potassium (Z=19) is 4.34eV, and the 4p--->4s transition occurs at approximately 768nm. Use this information to find the values of the quantum defects \delta(0) and \delta(1) for potassium, and hence to estimate the wavelength of the 6p--->4s...

Homework Statement 27 drops of salt water with same radius, are each charged to a potential of V volts. They are made to coalesce into a single drop. How is the potential of a new drop compared to the potential of the original drops. Homework Equations V ( potential ) = k* q/r...

Homework Statement A magnetic field of a long straight wire carrying a current I along the z-axis is given by the following expression: \mathbf{B} = \frac{\mu_0I}{2\pi} \{\frac{-y}{x^2+y^2} \hat{x} + \frac{y}{x^2 + y^2} \hat{y} \} Find two different potentials that will yield this field...

Homework Statement So, first of all, here is a drawing of a circuit: http://img253.imageshack.us/my.php?image=hexabj4.jpg The resistance of each hexagon wire is r. I need to find the resistance of this circuit when it is connected to the source with points A and B. I know that in...

Homework Statement The capacitors in the figure are initially uncharged and are connected, as in the diagram, with switch S open. The applied potential difference is V_{ab}= + 210 {\rm V} . What is the potential difference V_{cd} ? What is the potential difference V_{ad} after the...

If the private messages supported latex, I could ask this directly from meopemuk, but I'll put the question here now. (Edit: very logical, I'm not even using latex here... well maybe the replies use latex) meopemuk, these instantaneous potentials you have been talking about seem very confusing...

I'm looking for a good book for graduate students that indicates how one can obtain a (classical) potential from a tree-level Feynman process. For example, how can one go from the S-matrix of e.g. Compton scattering and derive the Coulomb potential. Any help would be appreciated.

Hi, folks, Is the exponential (repulsive) term in Born-Mayer potentials supposed to be exp(-r) or exp(1/r)? - r is the interatomic distance; constants ignored I've seen both versions pop up in what appear to be reputable sources. The second one seems to be more popular, but, to me at...

Hi folks, A while ago I started a thread on N=2 SUSY QM, but unfortunately (fortunately?) the progress in my research is outpacing the progress in that discussion. :-p So I'm leaving that one on the back burner to skip ahead to shape-invariant potentials. I'm working from Chapter 5 of...

My question arises from study during my Human A+P class, but it goes beyond what I'd be expected to know for the class so I decided to post it here. When potassium exits the cell body during repolarization, is this due to its concentration gradient? If so, why does the chemical gradient get...

Homework Statement Use half-reactions and E's to determine the result of storing a solution of CuSO4 in a tin container. Homework Equations [Table of Standard Reduction Potentials of Half-Cells] The Attempt at a Solution My question isn't exactly how to do this question. I was just...

Hello, I am not sure if this is the right place to ask this, but I don't readily see a "numerical methods" forum here so I assumed this would be the place to go. Sorry if I overlooked another place to post this! Anyway, I have some points interacting via potentials that are dependent only on...

Homework Statement Suppose a wire carries a current such taht I(t) = 0 for t< = 0 = k t for t > 0 Find the electric and magnetic fields generated 2. The attempt at a solution trying to figure out vector potential first looking at the diagram s is the distance fro a point P to the wire which...

Homework Statement Homework Equations E=hc/λ? and the Time Independent Schrodinger Equation. The Attempt at a Solution Now, would I be right in thinking for the first section that the energy for the E=hc/λ bit is just the energy of the particle given in the question (10eV)...

Homework Statement Point X is 0.25m away from a point charge of +4.7 E -8 C, point Y is 0.65m away. What is the potential of point X with respect to point Y? Homework Equations delta Ep=delta Ek V=delta Ep/Q delta Ep=QV Ep=kQQ/d The Attempt at a Solution delta Ep = -Ep1 W=QV...

I'm attempting to reproduce the results in http://arxiv.org/PS_cache/hep-th/pdf/0611/0611332.pdf , notably the V_F(T) potential involved with the Kahler potential K = -2 \ln \left( \hat{\mathcal{V}} + \frac{\hat{\xi}}{2} \right) W = W_{0} + Ae^{-aT} \hat{\mathcal{V}} = \gamma...

Say you have a spherical conductor of radius a located inside the cavity of a larger spherical conductor of radius b, and that the larger sphere's outer radius is c If you charge the inner conductor at a to a charge Q, the inside part of the outer conductor becomes charged -Q and the outer...

I know the following ion/inside cell/outside cell Cl- 5mM 150 mM K+ 130mM 5mM Na+ 20mM 140mM Ca2+ 10^-4mM 2mM How would I find the reversal potential for conductance equally permeable to sodium and potassium? How do I find the reversal potential for a conductance equally permeable to...

I know the following ion/inside cell/outside cell Cl- 5mM 150 mM K+ 130mM 5mM Na+ 20mM 140mM Ca2+ 10^-4mM 2mM How would I find the reversal potential for conductance equally permeable to sodium and potassium? How do I find the reversal potential...