We’re rewarding the question askers & reputations are being recalculated! Read more.

Questions tagged [potential]

Scalar and vector potentials in electromagnetism. The scalar potential is potential energy per unit charge. For potential energy, use the potential-energy tag.

Filter by
Sorted by
Tagged with
0
votes
1answer
13 views

Sources of Electromagnetic Potentials

I have a question regarding sources of electromagnetic potentials: As far as I know, wave equations for the scalar and magnetic vector potentials can be derived from Maxwell equations employing the ...
0
votes
2answers
21 views

Working of potentiometer to measure unknown emf

How at balancing point in a potentiometer does the galvanometer record zero deflection? Why is no current flowing at this point of time in the secondary circuit? Can someone explain what is going on ...
1
vote
1answer
70 views

What is the use of resistors connected in series?

If the current in a series circuit remains the same, then what is the use of a resistor? I read somewhere that as electrons flow through a circuit, they are accelerated towards the positive terminal, ...
0
votes
2answers
57 views

Derivation of Lagrangian of electromagnetic field from Lorentz force

I was trying to derive Lagrangian for electromagnetic field from the Lorentz's force formula $$F= q(E + v✕B)$$ I have to find the potential by using line integral of the force. I have wrote the above ...
2
votes
1answer
42 views

Explicit form of S-matrix on the line

Consider the Hamiltonian $H$ on functions on the line with \begin{eqnarray} H=H_0+V,\\ H_0=-\frac{1}{2m}\frac{d^2}{dx^2} \end{eqnarray} where $V$ is a potential vanishing outside of a bounded interval....
0
votes
4answers
104 views

Why do we pick trigonometric solutions, instead of complex exponentials, when solving the Schrödinger equation for a square well?

I was thinking about something that I never understood when I took my QM course. If I have an infinite square well, say $V=0$ for $ -a<x<a$ and $V= \infty$ otherwise. In the region of interest, ...
2
votes
3answers
65 views

Electron volt $eV$?

$1 eV$ is defined as the energy gained by an electron when accelerated through a potential difference of $1V$. But, I think when the electron is accelerated, it gets closer and closer to the source of ...
0
votes
0answers
26 views

Local density approximation: How do I get an expression for exchange and correlation for an atom?

I want to make a DFT program for an atom in the local density approximation. The user specifies the proton number and electron quantum numbers $n,l$, and the program returns the ground state energy by ...
2
votes
3answers
50 views

What determines whether we use a vector or scalar potential?

I understand that electrostatic potential is scalar because the curl of the field is zero, and this implies the electrostatic field is the gradient of the scalar potential to satisfy this. Similarly ...
0
votes
1answer
32 views

Potential Drop across a Capacitor

Let us consider an ideal parallel plate capacitor in a circuit. The capacitor is connected to a battery which generates a potential difference of V across the terminals. QUESTIONS: 1) The work ...
0
votes
2answers
22 views

Equipotential Lines

In 2D why exactly do lines of equal potential exist on a point charge at rest? This doesn't make sense to me if the point charge is hypothetically a lone charge undisturbed by other charges.
2
votes
1answer
52 views

Density functional theory: How do I derive potentials $V[n]$ from expressions for the energy $E[n]$?

In the following, suppose $n$ is the electron density and $n^\uparrow$ and $n^\downarrow$ denote the density of spin up and spin down electrons respectively. Therefore $n = n^\uparrow + n^\downarrow$. ...
0
votes
0answers
82 views

Are those two capacitors in parallel?

I'm trying to analyze the following situation: we have a parallel plate capacitor where the plates are both squares with side length $l$ and on the positively charged plate we have a charge $Q$, ...
-1
votes
1answer
24 views

Electric Potential of Two Oppositely Charged Adjacent Spheres [closed]

I am confused about part d to the following question (defining the reference point $\displaystyle\lim_{x\to\infty}\phi(x)=0$). My instructor has told me that $\displaystyle\lim_{x\to-\infty}\phi(x)=0$...
1
vote
0answers
22 views

A vector potential of a magnetic field and the gauge freedom of the Lagrangian

I'm currently studying a course of mechanical analytics. we used some terms that I just can't wrap my head around. I was wandering if anyone could explain\refer me to a good place to read about it: ...
1
vote
2answers
95 views

Calculating the point charge potential via Gauss's law

I want to calculate the potential of a point charge via Gauss's law $$\vec{\nabla}\cdot\vec{E}=4\pi\rho(\vec{r})$$ My Idea: we can find an expression for $4\pi$ that has the form of an integral, by ...
0
votes
0answers
20 views

Multipole expansion

consider a charge distribution say q, 2q, 3q, kept on the vertices of an equilateral triangle. There exist monopole, dipole ,qudrupole etc terms in the potential expression. these 3 charges are ...
0
votes
0answers
21 views

Quantum scattering from delta potential Barrier and well

Scattering from delta potential potential at $x=0$ it is observed that for $E>0$ both for potential well and barrier the reflection and transmission coefficient becomes same.As, in both the context ...
0
votes
3answers
27 views

Is electric potential of the grounded conductor of a capacitor always zero?

In a spherical capacitor, the net electric potential on the outer grounded conductor due to the positive charge on the inner conductor and the negative charge on the outer conductor is always zero. Is ...
0
votes
0answers
11 views

Spectrum of an operator with a center of attraction [duplicate]

What can we qualitatively say about the spectrum of a Hamiltonian operator if the spectrum is not bounded from below but bounded from above? e.g. $$\mathcal{H}=-\frac{d}{dx^2}-\frac{\lambda}{x^2}$$ ...
0
votes
1answer
17 views

Perfect Electric Conductor with applied voltage source

Let’s consider a perfect electric conductor which is connecting the terminals of an ideal voltage source (it is a short circuit in practice). What happens from an electromagnetic point of view? We ...
1
vote
0answers
34 views

Boundedness and energy spectrum

Consider the following potential with $g>0$: $$V(x) = \frac{g}{x^2}-\frac{\Delta}{4}x^2.$$ For $\Delta=0$, the potential is bounded from below because it decreases monotonically to zero. For $\...
0
votes
2answers
45 views

Why is a sum remaining here?

Substituting eqn (5.9) into the time-dependent equation gives $$ i\hbar \sum_n \dot c_n(t) |u_n\rangle e^{-iE_nt/\hbar} = \sum_n V(t) |u_n\rangle e^{-iE_nt/\hbar}c_n(t) \tag{5.10} $$ Now take the ...
0
votes
1answer
46 views

What's the difference between repulsive Delta function and Attractive Delta Function?

What's the difference between repulsive Delta function and Attractive Delta Function? I need to clear the concept. Please note that I know what's the Delta function.
0
votes
0answers
20 views

Charged disk inside a conducting spherical shell

I was doing a problem where we have a circular disk of radius $b$ and a grounded spherical conducting shell of radius $a < b$. The task is to find the electric potential everywhere. I was going to ...
0
votes
2answers
83 views

Why does the finite square well in 3D only admit odd radial solutions?

In these MIT Lecture notes (section 4.1.2, Page 7(53)) it says: "We must then choose the odd-parity solution in order to obtain a finite wavefunction at $r= 0$. Thus in 3D, only ...
0
votes
0answers
29 views

Can't get correct sign of electric potential of dipole

We have a dipole and I need to find $V(x)$ for $x<-d$ First I calculate the potential at some point $A=(x,0)$ relative to $P = (-\infty, 0) $ of the $-Q$ charge as follows $$\int_A^P\vec {E} \...
0
votes
1answer
12 views

Different electric fields

What is the difference between an $electrostatic$ and a $non-electrostatic$ electric field?
0
votes
1answer
50 views

Why net EMF in series connection of cell is sum of individual EMF? [closed]

Suppose we have two resistor and let A,B,C be points across resistors.Va-Vc=Va-Vb+Vb-Vc.Thus pd across the resistor combination can be obtained by simply adding the individual pds across each resistor....
0
votes
1answer
79 views

Solving Laplace equation in Cylindrical coordinates with azimuthal symmetry?

I am having some trouble solving what the potential field looks like for a finite cylinder along the $z$ direction. Physical Scenario Consider a cylindrical electrode with radius $R_0$ that extends ...
0
votes
1answer
31 views

Trying to define the electrostatic potential of a point charge

I've been trying to define the electrostatic potential (V) for a while now, it's something that I've covered last year and now need to know what exactly it does mean, I came up with this and all I ...
0
votes
0answers
17 views

Boundary Potential Problem- parallel alternating potential [closed]

I have question like this; I am confused about the solution. First I try to solve like 2D Laplace equation but I am not sure now, because there is no boundary condition parallel to the x. So I tried ...
-2
votes
3answers
114 views

Potential drop in a resistor

What causes a potential drop in a resistor or load? Why a does wire with neglible resistance have the same potential across it?
1
vote
1answer
34 views

Electric potential and its signs

When we are calculating the potential due to the sphere, why do we integrate from $r$ to $\infty$ instead of from $\infty$ to $r$? Or do we integrate from $r$ to $\infty$? Regardless of who does the ...
1
vote
1answer
42 views

Potential of hydrogen atom solution of the Laplacian: Missing boundary condition to fix integration constant $c_1$

I have following problem, I want to calculate the classical potential $\phi(r)$ of the hydrogen atom in its ground state. The charge density is known: $$\rho(r)=\frac{-e_{0}}{\pi a^3}e^{-\frac{...
0
votes
1answer
39 views

Why are induced field lines circular?

Whenever we have a changing magnetic flux through a conductor an induced electric field is generated. It is often said that these induced electric field lines are circular in shape.But why is this so?...
0
votes
1answer
35 views

Why can two nodes at the same potential be collapsed into one node?

I have a problem where I have a cube with resistance $R$ along each edge. I am asked to find the potential between various nodes (corners) using symmetry and the fact that two nodes at the same ...
0
votes
1answer
32 views

Misunderstanding the calculation of the potential for a system of 2 concentric shells

Let's say we have 2 concentric shells. The little one has a charge $Q_1$ and a radius $R_1$ and the greater one has a charge $Q_2$ and a radius $R_2$ with $R_2$ > $R_1$. We want to calculate the ...
2
votes
1answer
23 views

Point with 0 electric field and non-zero potential

I'm quite new to physics and I don't totally understand the concepts of potential energy and work. I've been watching MIT courses and I got pretty confused, considering the following situation: We ...
0
votes
1answer
37 views

Electric potential due to two spheres

The setup is as below: The two conducting spheres, of radii $r_1$ and $r_2$ have charges $Q_1$ and $Q_2$. The distance between their centers is AB. BC is perpendicular to AB. The problem asks to ...
1
vote
4answers
51 views

The potential at a point

According to my book, 'The potential at a point is said to be 1 volt when 1 joule of work is done in bringing 1 coulomb charge from infinity to that point.' But I wonder how it is possible. As the ...
0
votes
1answer
37 views

Difference of potential between 2 disks of radius $R$ where $d << R$

Well, We have 2 disks of radius R where the distance between these 2 disks : $d << R$. These disks are uniformly charged. I have calculated the electric field near one disk, I have: $$E(z) = \...
0
votes
0answers
34 views

Finding the potential off axis of a uniformly charged disk

This is problem 3.22 from Griffiths We know the potential at any point on the axis perpendicular to the center of the disk, I'm asked to find the potential at any point $(r,\theta)$ assuming $r<R$ ...
0
votes
0answers
11 views

Potential functions for separation and isochronic gauges

Most potentials in physics are expressed as a radius or another geometric norm/gauge. I am looking to understand the significance of the choice of potential functions for force/pressure separation in ...
2
votes
3answers
76 views

Magnetic Vector Potential - a measure of Momentum

I am trying to understand the magnetic vector potential as momentum per unit charge, that is, somehow, the "total" momentum should be $p = mv +qA$. Here's a part of the paper I was reading - I am ...
0
votes
0answers
37 views

Is there an accepted way to plot a wave function and the potential?

When using the time-independent Schrodinger equation and finding a wave function $\psi(x)$ for a given potential $V(x)$ is there a consistent way to plot these two objects on the same image that takes ...
0
votes
0answers
21 views

Central Potential + Coupled Angular Momenta

I am considering a two-state system with a Hamiltonian of the form $$ H = \frac{p_1^2}{2m_1} + \frac{p_2^2}{2m_2} + V_a(|r|) + \bigg(\frac{1}{4}-\frac{S_1\cdot S_2}{\hbar^2}\bigg)V_b(|r|), $$ where ...
0
votes
0answers
29 views

How to perform integration for all of space?

Two conducting spheres of radii $a$ and $b$ have charges $Q_1$ and $Q_2$. Distance between their centres is $R$. If ${\vec E_1}$ and ${\vec E_2}$ are electric field vectors due to the two spheres at ...
0
votes
4answers
102 views

Confusion about this simple electrostatics line integral

Suppose we want to find the electrostatic potential $\phi_{0}$, with reference to infinity, at $r_{0}$ resulting from a positive charge $q$ located at the origin. For simplicity, let us assume we are ...
0
votes
0answers
30 views

Boundary conditions for an infinite line charge and grounded conducing plane

I'm not asking for a solution to the problem, I'm confused about what I should set the boundary conditions to, it's obvious that $V=0$ at $z=0$ because of the grounded $xy$ plane, but I don't know ...