Questions tagged [dipole]

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Electric potential and force in terms of Rydberg

Given charges +Q and +q, separated a distance r[nm], find the electric potential and repulsive force. I am given a solution to a problem that is evaluated in terms of the Rydberg energy, but I don't ...
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Physics of an electrostatic water pump, is it even possible?

I have been trying to figure out how to approach this problem. Imagine a cylindrical shell made of insulating material. The top surface has a hole in its center, with a pipe extending up. The bottom ...
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Calculate the force acting on a dipole at an electric field [closed]

I have the following question: There are two electric charges at $(-a,0,0)$ and $(a,0,0)$ with the charge $Q$. A dipole with dipole moment $\vec{P}_{el}$ is placed at $(0,0,0)$ and is oriented in the ...
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Is there a similar process like hysteresis for dielectrics/dipoles?

Hysteresis is shown in the following image from hyperphysics: Does a similar curve exists for dipoles? For example given a dielectric medium inside a capacitor, the electric field will induce a ...
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DC Bias Characteristic of Ceramic Capacitors under Transient

It's pretty well documented that many ceramic capacitors will "shed" capacitance with increasing DC bias. Seems that the mechanism is pretty well outlined too. (The physics behind DC voltage ...
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Confusion about exact electrostatic potential of a pure dipole [duplicate]

I asked a version of this question before but the phrasing was unclear, so don't mind me please. Suppose you have a physical dipole with equal and opposite charges Q and -Q, with a specified dipole ...
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Electrostatic potential due to a pure dipole

For a pure dipole, is the electrostatic potential given by the dipole term in the multipole expansion exact for all $r$ (position vector from the origin)? Or is it exact only far away from the dipole? ...
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What will happen when external magnetic filed disappear suddenly in Larmor precession?

Larmor precession is a phenomenon that when we place a magnetic dipole in the external magnetic field, the magnetic dipole will rotate around the direction of the magnetic field. But I am not quite ...
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Charge density of Hertzian dipole

I am wanting to find the charge density of an infinitely thin Hertzian dipole, but am struggling evaluating the Dirac delta functions gradient. $$\vec{J} = I_{0}\cos(\omega t) \delta^3(r) \hat k.$$ ...
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Force between two dipoles [closed]

I am extremelly confused with this question: Basically suppose we have two electric dipoles, parallel to each other, as follows in the figure: I am supposed to show that the force is attractive and ...
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Does the 'internal potential energy' (created by charge separation) of a dipole have any physical meaning?

If you have a dipole with charges $Q_+$ and $Q_-$ separated by a distance $d$ you could calculate the work done of separating these two charges the distance $d$ $$ \Delta U = q \Delta V = - \vec{F} \...
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How to find field strength of magnetic field of an oscillating dipole without $x,y,z$ variables?

(For better viewing, visit https://lateral-bathroom-f63.notion.site/How-to-find-field-strength-of-magnetic-field-of-oscillating-dipole-without-x-y-z-variables-ea0d864f371e4649a21d6cf5d007f9ee) I have ...
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Is the Lorentz force law really the full (classical) characterization of how particles react to the EM field?

Classically, the effect of the electromagnetic field on particles is often said to be given by the Lorentz force law: $$ \vec{F} = q\vec{E} + q\vec{v}\times\vec{B}. $$ However, I'm really starting to ...
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About dipole moment

The picture is taken from wikipedia page https://en.wikipedia.org/wiki/Electric_dipole_moment I don't understand the formula when it comes to continuous charge distribution. But I understand this one: ...
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Why is the magnetization inside a diamagnetic material antiparallel to the external field

Let's say I have a constant magnetic field and I dive into it a diamagnetic material. Griffiths says that in the presence of a magnetic field, matter becomes magnetized and it will be found to contain ...
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Formula for force on a magnetic dipole

Using the magnetic current model, the force on a magnetic dipole, commonly derived in textbooks, is found to be: $$ \mathbf{F} = \nabla(\mathbf{m} \cdot \mathbf{B}) \tag{1} $$ If the magnetic pole (&...
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Electrostatic potential of a dipole in a non-uniform field

There are numerous derivations for the potential energy of a dipole in a uniform field as: $$ U = - \boldsymbol{p}\cdot\boldsymbol{E} $$ But does this hold also for non-uniform fields? Are there any ...
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A positively charged objects move towards a negatively charged object, but it is a fact that protons do not move. How is that?

This is probably a very basic to most of you physics people but It's frustrating me and I need to get answers ASAP. Just saw an experiment on YouTube where they rub a silk on some sort of glass rod, ...
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Why does the dipolar Hamiltonian factorize after applying the rotating wave approximation?

The Hamiltonian for two interacting magnetic dipoles is $$H = \frac{-J_0}{r^3}\left[3(\vec{S}_1\cdot\hat{r})(\vec{S}_2\cdot \hat{r}) - \vec{S}_1\cdot\vec{S}_2\right]$$ here $\hat{r}$ is the unit ...
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Is it possible to have a particle with a positive and negative charge?

When you have two oppositely charged particles, according to Coulomb's Law $F=k q_1q_2 /d^2 ,$ the closer they are together, the greater the force they exert on each other. On some simulations I´ve ...
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Selection rules intuitive

The selection rules for hydrogen are: $\Delta l=\pm1$ and $\Delta m=0,\pm1$. The first makes intuitive sense because of the conservation of angular momentum and the fact that a photon has spin 1. But ...
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Bound charges in the surface of a dielectric

I am trying to understand how $\sigma_b=\vec P \cdot \hat n$. In wikipedia I found the correct derivation but I don't understand some things. There it is said: The bound surface charge is the charge ...
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Confusion in mutual torques between two dipoles, and Newton's Third Law

We have the following setup of two dipoles, separated by distance $x$ ($x>>$length of dipoles), and let us write dipole moment of horizontal one to be $p_1$ and other be $p_2$ setup: Now ...
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Is gravitoelectromagnetism monopole or dipole?

Thorns said gravitoelectrism is monopole whereas gravitomagnetism is dipole. Others are saying the latter is monopole: https://doi.org/10.1140/epjc/s10052-021-09696-3 Which on is most likely right? ...
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Why is the neutron electric dipole term CP violating?

I have heard that a term of the form $\bar{q}\sigma^{\mu\nu}q F_{\mu\nu}$ is CP violating but looking at any Textbook (e.g. Peskin Schröder) one can see that the CP transformations are the following: $...
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Electric dipole approximation for perturbation: What is this symbol and how was it part of this derivation?

I'm reading electrodynamics physics notes that describe the polarization of a medium. The notes describe the active atoms as having two levels $a$ and $b$, separated by energy $\hbar \omega$ and ...
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Why would magnetic monopoles not violate the law of conservation of energy?

The field lines around a magnetic dipole are continuous unending loops. If magnetic monopoles were to exist, we could limit the path of a monopole along one of these field lines where it will continue ...
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Electromagnetic radiation of dipole in the frequency domain

Recently I've met a formaula that says the radiation power of a dipole in the frequency domain is $I(\omega) = |\omega^2P(\omega)|^2$, where $\omega$ is the frequency of the radiation and $P(\omega)$ ...
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What is the field of a magnetic dipole near a conducting sphere?

Suppose I have a perfectly conducting sphere in vacuum, and I place a magnetic dipole near this sphere. Simply stated, the magnetic field of the dipole will be distorted by the presence of the ...
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Calculating work in an Image dipole method

I have encountered an Electromagnetism problem, which asked me to calculate the total work required to separate an electric dipole from a conducting plane. The dipole's moment was given $p$ and the ...
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What is the physical model for energy flow in or around an ideal conductor during transient analysis? (Veritasium Electricity in Wires)

Context Veritasium - The Big Misconception About Electricity - Energy Doesn't Flow in Wires: https://youtu.be/bHIhgxav9LY Simplified Context My question relates to the microscopic view of electric ...
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3 answers
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Why magnet is always a dipole?

Why magnet is alway dipole Even the atom of the magnetic substance is also dipole , how can small atom be dipole . Pls explain me
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Electric dipole for a continuous charge distribution

In Wikipedia https://en.wikipedia.org/wiki/Electric_dipole_moment it is said: More generally, for a continuous distribution of charge confined to a volume V, the corresponding expression for the ...
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Electric field and magnetic field from dipole radiation

The electric field and magnetic field from dipole radiation given in my book is: $$\overrightarrow{E}=\frac{\overrightarrow{r}\times(\overrightarrow{r}\times \overrightarrow{\ddot{d})}}{4\pi \...
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About applicability of Gauss’ law in electrostatics

While reading about Gauss’ law in electrostatics, I saw that we do not apply this law to evaluate the fields generated by dipoles, quadrupoles etc. It is only applicable to cases where the fields fall ...
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Multipole Expansion Intuition

So my intuition of the multipole expansion is that we have a certain charge distribution, and the ME tells us that we can approximate that distribution as a superposition of monopoles, dipoles, etc. ...
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Griffiths and Multipole Expansion, what is each variable in the equation?

Griffiths defines the formula for the multipole expansion as $$V(\mathbf r)=\frac{1}{4\pi\epsilon_0}\sum_{n=0}^\infty\frac{1}{r^{(n+1)}}\int(r')^nP_n(\cos\alpha)\rho(\mathbf r')\,d\tau'.$$ But I am ...
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2 votes
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Is an expression of a quadrupole as an expansion of dipoles possible?

Would it be possible to express a quadrupole as an expansion of dipoles? Because a possible definition of a quadrupole seems to be: an electric field equivalent to that produced by two electric ...
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It's a question of Electrostatics, where the force on dipole is to be determined by using the potential energy

$\text{In Electrostatics :: Force on Dipole : }$ $$\vec F = - \nabla U, \,\,\ \text{U= Potential Energy of Dipole}$$ $\because U=-\vec p \cdot \vec E$ $\text{How can we come to this result : }$ $$\vec ...
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Electric dipole moment and charge density

I came across the following expression about the electric dipole moment: $\vec p=\int_V \rho(\vec {r}')\vec r'$ But I don't understand it. What is $\vec r'$ supposed to represent and the density? Are ...
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Charge density of an electric dipole and dipole density

I am trying to visualize in my head and understand how the concepts of electric dipole charge density and dipole density can be interpreted in space or in a coordinate system. In our lecture the ...
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Molecular dipole moment transition in bra-ket notation

Below is equation for dipole moment transition: $$\langle \Psi_k| p |\Psi_i \rangle = \langle \Phi \chi_{N,k}|p_e+p_N|\Phi \chi_{N,k} \rangle = \langle \chi_{N,k}|\langle\Phi_k|p_e|\Phi_i\rangle |\...
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Why should a dipole have zero net charge?

Why can a dipole not have two unequal charges separated by a distance? Is there any significance for the dipole being defined as electrically neutral?
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Line integral across perfect dipole

In problem 4.7 of Griffiths' "Introduction to electrodynamics, 4th Edition", we are asked to find the potential energy of a dipole in an electric field, $\vec{E}$. In the solution, the ...
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Electromagnetic energy from a dipole antenna

Looking for references on previously done analytical development of the radiated field very close to a dipole antenna. I am not interested in a spherical coordinate system-based analysis, because that ...
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Why can a magnetic dipole have an energy in the magnetic field?

It is well known that the energy of a magnetic dipole in the magnetic field is given by $$ V = - \vec \mu \cdot \vec B $$ But I wonder how there can be a concept of energy at all. You can imagine the ...
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Why half-wave dipole is the most efficient one in comparison to other electrical lengths?

I have a problem on the understanding of a half-wavelength antenna. Namely, why is the half-wave antenna has a highest power emission. Considering Far Field factor F($\theta$), which is known from the ...
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1 vote
1 answer
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Electric dipole moment of a ring of charge [closed]

In my book dipole moment is defined for two charges. But I got a hw question to calculate dipole moment due to a ring. I tried two different methods to solve this problem but I don't think that any ...
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How do I determine the polarizability of a material?

Is there a simple and elegant way to determine the polarizability of a material? If so, how? Experimentally, one can easily measure the electric and polarization fields, but measuring polarizability ...
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1 answer
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Similarity between Potential Energy Function of Polarized Sphere and Cylinder

According to this paper, the potential of any point on the surface at a distance '$h$' from the center of some simple conducting geometric shape is given by For a Sphere: $$V(x)=Mh^2\frac{xcos(\alpha)+...
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