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
4answers
84 views

Ambiguity between electric potential and voltage?

I understand that electric potential is a location based measure of electric potential energy per unit charge in an electric field, and that voltage is then the difference between two electric ...
0
votes
1answer
36 views

Charged conductor in an external electric field

If we put a conductor in a place where there is a uniform electric field, then the field will change. Take for example the case of a conducting cylinder, then the field lines would curve to return ...
0
votes
1answer
90 views

What is the quantum mechanical turning point of the $n^{th}$ energy eigenstate of an oscillator? [closed]

I am looking for an analytical expression for the most likely position for a quantum harmonic oscillator (which I refer to as the quantum mechanical "turning points"), in terms of $n$. For the quantum ...
1
vote
2answers
71 views

On proving that charge is linearly proportional to potential for a conductor

In Mr. Purcell's Electricity and Magnetism, page 103, it is stated, An isolated conductor carrying a charge $Q$ has a certain potential $\phi _{0}$, with zero potential at infinity. $Q$ is ...
0
votes
0answers
37 views

One-dimensional Schrödinger equation: reproducing a given set of energy values [duplicate]

Given a set of $N$ increasing real numbers $\{E_1, E_n, \cdots, E_N \}$, is it always possible to find a potential $V(x)$ such that the set of $\{E_j\}$ are the lowest eigenvalues of the corresponding ...
0
votes
1answer
31 views

Is the $E$-field near and on the outer surface of a conductor null?

Let us say we have a conductor the outermost surface $S$ of which is given by $$S: \big(\,x(u,v),\, y(u,v),\, z(u,v)\,\big )$$ where $u$ and $v$ are parameters. Since it is a conductor, the ...
0
votes
0answers
13 views

Summation of piezoelectric potentials

I am looking at surface acoustic wave devices, these are piezoelectric circuit components. They use an electrode pattern, called an inter-digital transducer (IDT) to produced and receive Rayleigh (or ...
2
votes
1answer
41 views

Gravitational Potential Derivation

The definition of Gravitational Potential at a point is the work done per unit mass in moving it from infinity to that point. However the work is positive and if you perform the integral you get a ...
0
votes
1answer
51 views

What's the intuition for the reflection of a quantum particle at a potential step equal to the particle's energy?

While doing the problem of potential step, I saw that if the energy of the particle is equal to the potential energy of the step, then the wave function is a constant, or to say the probability ...
0
votes
1answer
48 views

Odd potentials in TISE

When we have an even potential we say that it has an even and odd parity wavefunctions, cf. e.g. this & this Phys.SE posts. What about an odd potential? For example, two delta functions centered ...
1
vote
2answers
161 views

From Poisson's equation to Laplace's equation [closed]

I want to understand how exactly $$ \nabla^2 V = - \frac{\rho}{\epsilon_0}$$ turns into $$ \nabla^2 V = 0.$$ Of course it is by setting $ \rho$ equal to $0$ but what does setting $ \rho$ equal to $0$ ...
0
votes
0answers
26 views

Why are so many (all?) Key concepts in thermodynamics derived from a legendre transformation? [duplicate]

Given a function $f(x,y)$, a legendre transform w.r.t. $x$ is $f^*(p,y)=p x - f(x,y) |_{p=\frac {\partial f(x,y)}{\partial x}}$. E.g. , the various free energies, enthalpy, etc are all legendre ...
0
votes
1answer
23 views

On setting the potential of this conducting sphere to zero

Let us say we have the following setting: Two conductors with potentials $\phi _{1}$ and $\phi_{2}$ (with the zero set to infinity) enclosed within a hollow conducting shell having zero charge. How ...
0
votes
1answer
53 views

Qualitative Nature of the wave function under a certain potential

By putting the values of V(x) at a and point b we get, $\frac{\partial^2\psi}{\partial x^2}=\frac{2m}{\hbar^2}(-v_1-E)\psi$ ...(1) and $\frac{\partial^2\psi}{\partial x^2}=\frac{2m}{\hbar^2}(-v_2-E)\...
0
votes
0answers
32 views

Average position in the Morse potential

Does anyone know the analytical expression for $\langleψ_n|x|ψ_n\rangle$ in the Morse potential? In other words, I'd like to find the average position of a particle at the $n$-th vibrational level in ...
2
votes
2answers
100 views

Potential for a general fictitious force?

In a general non inertial system four fictitious forces arise: Coriolis Force, centrifugal Force, azimuthal Force, "translational" Force (due to linear acceleration of the origin of the system) I ...
0
votes
3answers
49 views

Why is there a 1/2 in the expression for electrostatic energy U?

The expression for electrostatic energy is $$U= \dfrac{1}{2} \times \int \rho\,\phi\, dV$$ where $\rho$ is the charge density and $\phi$ is the potential at that point in ($dV$) Let me explain what I ...
1
vote
0answers
46 views

Wavefunction of particle in power law potential of type $x^a$?

How could we calculate the wave function of a particle under a potential of form $V(x)=x^a$? Is there any analytical solution or any general feature of such solution (like its an exponential ...
0
votes
1answer
75 views

${}$ Dirac delta potential

We know that the number of bound states for an attractive delta potential is one. If so what will the number of bound states for a particle in a repulsive delta potential? If $V(x)= +a \cdot \delta(x)$...
0
votes
1answer
40 views

Potential Drop across Inductor VS Potential drop across Rotating coils in $B$-Field

I was trying to understand the difference between the Back emf generated across Inductor due to change in current and Back Emf Generated across a coil that is rotating in presence of B Field. ...
0
votes
1answer
18 views

About fixing the potential on the surface of a conductor

In Purcell's Electricity and Magnetism, p.116 section 3.3, the author spoke about Laplace's equation and said that the boundary conditions for the potential$\,\phi$ on the surface of the conductor may ...
3
votes
3answers
115 views

Why don't capacitors hold charges on the outer walls of the plates? [closed]

Suppose I have two metal plates in a vacuum and I give this system some electric charge,the charge would distribute itself according to Gauss law on both the inner and outer walls of both plates...but ...
2
votes
0answers
21 views

Manev potencial and some problems with it [closed]

Given the Manev potential by the equation below $$\ V_M(r) = - \frac{-mMG}{r} \left(1 + \frac{\gamma MG}{c^2r}\right) $$ in which: M is the Sun's mass; m is the planet's mass; G is Newton's ...
1
vote
1answer
85 views

Energy eigenvalue with Potential $-e^2/ x$ [closed]

If I have potential which are very well-known like, square barrier, or square well, or step potential, What I do is to set the boundary conditions in Schrödinger's equations. Sometime, the ground ...
0
votes
1answer
47 views

Significance of the negative sign in $V=-\int \vec E · \mathrm d\vec r$ [duplicate]

Why is there a negative sign in the relation $$V=-\int \vec E · \mathrm d\vec r$$ between the electric field and the electric potential? Is this because of some derivation in vector calculus because ...
0
votes
1answer
24 views

On direction of electric field in a battery

I know that the electric field points from positive to negative potential in a circuit but it is opposite inside a battery for the purpose of continuity of electron flow and electric field....but why ...
0
votes
1answer
48 views

The pair potential different that $r^{-1}$

As I know, the potential between two particles of the form ~ $r^{-1}$ ($r$ is distance between particles) is special, because it solves the Poisson's equation in 3D. My question is: If I consider for ...
0
votes
2answers
60 views

Commutation with unspecified potential function

Instead of a potential given like $V(r) = k r^2$ or $V(r) = y^2$ , if the potential is given like in the form a function but not clearly specified, can we tell that if that commutes with the ...
0
votes
1answer
98 views

Potential energy of electric dipole

While deriving the formula for potential energy of electric dipole I almost every time see that while the torque was demanding the dipole to rotate in one direction , we let the dipole to rotate in ...
2
votes
2answers
124 views

Newton's Universal Law of Gravitation doubt

The Universal Law of Gravitation states that the module of the force, $F$ is $$F = \frac{GmM}{r^2},$$ where $m$ and $M$ are the mass of the two objects and $r$ is the distance between the two objects....
0
votes
1answer
45 views

Bound states and parity for a arbitrary potentials

If we are given an arbitrary potential, and we are asked to find bound states and parity, what would be usual strategy to do that? Let's we have a potential given: $$-\frac{A}{y^2+a^2} -\frac{A}{(y-...
0
votes
0answers
40 views

Rescaling the Uehling potential formula

I found that the Uehling potential equation is written in natural units in many books and research papers. But because I’ve to make some calculations with the Uehling correction, the formula must be ...
1
vote
0answers
57 views

Issue with solving for the wavefunction of a simple infinite potential

For the potential given by $V(x)=\left\{\begin{array}{ll}{\infty} & {x<0} \\ {-V_{0}} & {0<x<a} \\ {0} & {a<x}\end{array}\right.$ I am trying to solve for the wavefunction. ...
0
votes
0answers
47 views

Finding potential in spherical coordinates using Laplace equation

In Griffiths electrodynamics in an example it evaluates the potential inside a hollow sphere of radius R having potential $V_0(\theta)$ potential inside is the form of this $$v(r,\theta) = \sum A_lr^...
0
votes
1answer
49 views

What does Ohm's law mean in this context?

In this problem Griffiths states that the potential at radius $a$ and angle $\phi$ is $V(a,\phi) = \frac {V_0 \phi}{2 \pi}$ And yes that satisfies the boundary conditions, that at $ \phi = \pi$ , $ V=...
1
vote
2answers
199 views

What is the work done in bringing a charge from infinity to the location of another point charge?

Consider a positive charge $Q$ at the origin.What is the work done in bringing a unit positive charge from infinity to zero. We know that the work done in bringing the charge from infinity to $r$ is ...
0
votes
0answers
6 views

How do you calculate a half cell potential Copper(II) and Copper Sulfate?

I have to complete an experiment for school where I have copper and zinc electrodes placed into an electrolyte of copper sulfate and I have measured the potential across it at varying temperatures. ...
0
votes
0answers
17 views

Can electric fields pass through grounded surfaces?

Let's assume there is a grounded surface with which is infinite in length and width. If my understanding is correct, the grounded surface should have zero electric potential. So, if we assume an ...
0
votes
3answers
120 views

Expected value of Momentum in a square infinite well [closed]

Say I have a particle with mass $m$, in a potential infinite well centered at $x=0$ with length $d$ which wave function at $t= 0$ is represented by: $$\Psi(x)=\begin{cases} \frac{1}{\sqrt{2}}\left[\...
0
votes
1answer
20 views

Electric potential difference between capacitor's plates, doubt about the sign?

I'm trying to solve a doubt that has taken me away way too much time and so I'm asking here. In our lectures we defined the electric potential difference between a point A and B as the line integral ...
5
votes
1answer
96 views

What potentials have infinitely many bound states? [closed]

Some potentials have only finitely many bound states (the finite square and delta function are two good examples) Others have infinitely many bound states (for example the infinite square well and $1/...
0
votes
1answer
100 views

Gaussian wave packet with a step potential

In principle of quantum mechanics by Shankaar on page 170, while doing transmission and reflection index for a step potential for a Gaussian wave packet moving to the right. We come to this ...
1
vote
3answers
122 views

Negative energy in bound states of a particle in a finite potential well

Consider you have a particle in a finite potential well as depicted in the photo attached. Now we have three regions: $$V(x) = \begin{cases} 0, & \text{for } x<-a & (1)\\ -V_0, & \...
0
votes
2answers
61 views

Metal sphere in uniform Electric Field—doesn’t behave like dipole at large r?

I’m going over Griffiths EM example 3.9 (different question on this example is here Metal Sphere in a Uniform Electric field). I’m wondering where the logic for $$V\rightarrow -E_0z= -E_0r\cos(\theta)...
6
votes
1answer
85 views

Do potentials make sense in relativistic quantum theory?

In Peskin & Schröder QFT, just before equation 7.93, he writes in passing, Next let us examine how $\Pi _2 (q^2)$ modifies the electromagnetic interaction, as determined by Eq. (7.77). In the ...
0
votes
0answers
38 views

Electric potential difference between coaxial cables clarification

https://www.youtube.com/watch?v=hJPWs0Gf2SU In this video, he derives an expression for the potential difference between the two radii R2 and R1 where R2>R1 He arrives at the derivation by ...
1
vote
1answer
68 views

Potential and potential energy

I know when a negative charge moves in the direction of a uniform electric field its potential energy increases and its potential decreases. For example, its potential energy changes from $0.9\ \rm{mJ}...
0
votes
1answer
86 views

Ways to understand spatial symmetry [closed]

If you are given a potential, which doesn't change if you change the azimuthal angle, we might call that has spherical symmetry. Which means we must find symmetry of angular momentum $L_Z, L^2$. My ...
0
votes
0answers
56 views

What makes Earth's orbital motion and the motion of a pendulum both periodic? [duplicate]

What is the commonality which makes the motion of a bob attached to a spring , motion of a pendulum with any amplitude or that of the earth around the Sun all to be periodic despite very different ...
2
votes
2answers
68 views

Common potential in Capacitors

If two isolated charged capacitors (of different capacitance) are connected in parallel to each other they acquire a common potential. But suppose if i connect positive plate of one capacitor to ...