Questions tagged [dipole]

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What is the **electrostatic** potential energy of the dipole? [closed]

An electric dipole consisting of charges q and -q separated by a distance L is in stable equilibrium in a uniform electric field E. What is the electrostatic potential energy of the dipole? A)qLe B)...
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1answer
51 views

Electric field outside a conductor

Say there is a conducting cylinder in a uniform external field. The charges on the cylinder surface will distribute and create a surface charge density. Is there any reason the charge density would ...
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1answer
34 views

Dipole oscillators question from Feynman lectures 1.28-29

I am confused by the Feynman lectures Vol1Ch28-29. In all the pictures, there is an electric dipole oscillating vertically. We're assuming the intensity is $E^2$ and that in the far r limit $E$ ...
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1answer
50 views

Question about perturbation theory and even and odd wavefunctions

I was solving a question about perturbation theory and I came across something my teacher didn't mention and I can't seem to understand it. In the question there is an external electric field on a H-...
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17 views

Dipole in a dielectric

Intro to electrodynamics,David J. Griffiths Problem 4.37. A point dipole p is embedded at the centre of a linear dielectric material.Find the electric potential inside and outside the sphere. I know ...
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2answers
28 views

Direction of Force on a Dipole in a given Electric field

How should I determine the direction of the force in the given case: (p is the electric dipole moment) Using the following formula My book has the following : I am unable to understand the given ...
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1answer
25 views

Electric Dipole inside a cavity of conducting sphere [closed]

In the problem, a cavity is taken out of a uniform conducting sphere. Inside the cavity, a dipole is placed as shown in the fig. find the potential at point P
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21 views

Work done in rotating a dipole in NON uniform electric field [duplicate]

I understand that the torque on a dipole due to a non uniform electric field is given by the same expression as that of in a uniform electric field i.e. pEsinθ. Now,how do you calculate the work done ...
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27 views

A non-uniformly polarized sphere

When we have a polarized sphere (say with polarization density $\vec{P}=\alpha r \hat{z}$ for example) and we calculate the electric potential inside, why do the dipoles outside where we calculate don'...
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1answer
53 views

Dipoles in 2D and 'dipolar line'

I am currently studying the textbook Surface Enhanced Raman Spectroscopy -- Analytical, Biophysical, and Life Science Applications by Sebastian Schlücker, Wolfgang Kiefer. Chapter 1.2.3.2 Localized ...
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2answers
51 views

Theoretical value of electric dipole moment of a molecule

Consider a hydrogen chloride molecule (HCl). Let's assume that we're given the distance between hydrogen and chlorine nuclei $d=1.27 \times 10^{-30} \mbox{m}$. How to calculate electric dipole moment $...
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In di-electric does number of dipole or dipole moment of individual dipole vary?

Let's say we have an insulator, and we have an external electric field passing through it. We know that there will be an induced dipole and polarization in the atoms of that material(It's mentioned on ...
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Why do you add two different contributions when calculating the potential energy for point-charge point-dipole system?

In https://janheyda.files.wordpress.com/2015/08/electrostatics-multipoles.pdf Masahiro Yamamoto states that: the potential energy required to bring a point charge of charge $z_ie$ to a distance $r_{...
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What is the force between a charge and a dielectric (polarized in the presence of charge)?

We know the reason why a charged balloon will get attracted to the wall is because of polarization. But how can we calculate the force between the polerized dielectric and a charge depending upon: ...
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1answer
36 views

Why are domains formed as separate units?

I was reading about exchange coupling and domain formation in ferromagnetic materials. As far as I can understand, some of the dipoles in the ferromagnetic material align themselves in a group called ...
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1answer
38 views

What's the connection between complex charge, complex dipole, and complex electric field?

In standard EM course, the complex EM field was emphasized and studied. However, the complex dipole moment, such as time harmonic dipole moment $\vec{p} \exp{i\omega t}$ was less investigated, as ...
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26 views

What it the force on a electric dipole moment under external constant magnetic field?

I know that the following formula $$F=\vec{v}\times(\vec{p}\cdot\vec{\nabla})\vec{B}+\dot{\vec{p}}\times\vec{B}$$ is valid but can someone provide me with a intuitive/mathematical proof?
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2answers
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Curl of electric field due to dipole?

The field lines of electric field of dipole do seem to curl if seen geometrically. If water flow lines were of such shape, a ball would have rotated in it, doesn't this interpretation of non-zero curl ...
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0answers
24 views

Non $1/r$ distance dependence for Voltage from dipole radiation

I am getting a strange result with an underwater measurement. When I test the distance dependence of a very low frequency EM wave underwater (1.5kHz), it is much, much shallower than the expected 1/r ...
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27 views

Question on Earnshaw's theorem and periodic motion

This is one of the problems I've encountered while doing questions on dipoles: Place an electric dipole $\vec p$=$\hat p$$z$ at the origin and release a point charge q (initially at rest) from the ...
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6answers
175 views

Why is electric field of dipole nonzero?

Why is the electric field from a dipole nonzero? Intuitively, I know there are electric field lines going from the positive to negative charge, so there should be an electric field. But if I apply ...
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30 views

Minimal coupling to electric dipole form - II

In addition to link, may I ask you for details of the Hamiltonian transformation. Knowing that: $[\textbf{x},\textbf{p}]=i\hbar$, $[\textbf{x},\textbf{p}^2]=2i\hbar\textbf{p}$ and $e^{-i\alpha A}Be^{...
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Is there a code for Ewald Summation for Dipoles?

Does anybody know if there exists a code that calculates the potential energy for a system with both point charges and point dipoles using Ewald summation? This would be a great help to my Master ...
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1answer
46 views

Minimal coupling to electric dipole form

When deriving the electric dipole form of the semiclassical hamiltonian from the minimal coupling form, we define a new state vector as: $$\psi_{old}=e^{i\textbf{A}\cdot\textbf{x}/\hbar}\psi_{new}=\...
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67 views

Why finite potential but no stored kinetic energy in an electric dipole?

have read that potential energy is stored kinetic energy that is if the the body is left free it will start moving, at the mid point of two opposite charges, the charge starts moving even though the ...
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2answers
65 views

Can we understand a moving charge as a dipole?

I work as a physics teacher at a high school and I have to explain these days the magnetic field of a curreny carrying wire. Of course I may just give the formulae and describe how the field $\vec{B}$ ...
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1answer
30 views

How to take the gradient of the dipole dipole interaction energy?

This answer (Force between two point dipoles) was very clear; however, I am having trouble understanding how to take the gradient of $$U = \frac{p′⋅p}{r^3}−\frac{3(p′⋅\vec{r})(p⋅\vec{r})}{r^5}.$$ with ...
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How does a mobile patch antenna receive the correct signal in any orientation and rotation?

For instance if we take a dipole and then rotate the receiving dipole 90 degrees such that it forms a cross against the transmitting dipole, would the signal be retrieved at all? If it were rotated ...
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1answer
129 views

Direct detection of the electric field of an electromagnetic wave from an oscillating dipole

The principle behind the detection of gravitational waves is that stellar-mass sources can act as coherent oscillators, producing a gravitational wave with a well defined, and relatively slowly ...
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1answer
100 views

How is the two-level atom dipole force modified for a real, multi-level atom?

I was trying to compute the dipole force exerted by a laser beam at $1064$ nm on a $^6{\mathrm{Li}}$ atom (the most important transition being around $671$ nm, the laser is greatly red-detuned), when ...
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3answers
68 views

How can sawdust do this in an electric field?

I found this really weird question and I was hoping for some insight. Suppose we have a glass plate that's filled with oil. Some sawdust is sprinkled on top, such that it floats around. It looks like ...
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1answer
48 views

Electric energy from dipole moment

Conventionally one define electric energy as $$ U = \frac{1}{2} \int \vec{E}(r') \cdot \vec{E}(r') d^3 x' $$ where $\vec{E}$ is a Electric field. And from textbook like Griffith, we know that ...
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1answer
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Questions on Forces involved in oscillating mass dipole

Say we have two balls of radius $R$ on both sides of a massless dielectric rod and it starts oscillating due to an external electric field. Other than the external field would there be an electric ...
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1answer
45 views

Energy of a dipole?

Suppose that we have a perfect dipole with $+q$ at $\vec{r}+\vec{d}$ and -q at $\vec{r}$, and that this dipole is in a uniform electric field $\vec{E}$, Then: \begin{equation}U=-\vec{p}\cdot \vec{E}....
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1answer
164 views

An electric dipole placed in a non-uniform electric field

Can an electric dipole placed in a non uniform electric field (say as that of an infinite line charge) ever experience a zero net force and simultaneously a zero net torque on it? I know about the ...
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2answers
87 views

Why is dipole potential independent of azimuthal angle?

In the formula for dipole potential in spherical coordinates, there is no dependence on azimuthal angle. I don't see why this is as by varying the azimuthal angle, i.e changing our position on the x y ...
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Calculation of the static dielectric constant/relative permittivity of water is not leading to a reasonable answer. Can anyone help me understand why?

I want to calculate the static dielectric constant/relative permittivity of water ($\varepsilon$). People have measured it at a temperature of 20 C; it is around 80. However, I'm doing something ...
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1answer
52 views

Confused about electric dipole

Up to this point I know that two equal and opposite electric charge constitute an electric dipole. But when I study the "Introduction to electrodynamics" by DJ Griffiths, the author a consider a ...
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9 views

periodic images of dipole line charge followed by vacuum, electrostatic potential?

I am trying to calculate the potential due to a dipole line charge placed at the interface of a 2d lateral metal-semiconductor junction followed by vacuum and this system repeats itself. Could someone ...
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32 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} \...
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22 views

Definition of $H$-field with Magnetization

i am trying to understand the H-field more intuitively. My textbook defines the H-field as follows: $\vec{B} = \mu_0 (\vec{H}+\vec{M}) $, where $\vec{M}=\frac{\sum_i{p_i}}{V}$ is the magnetic dipole ...
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1answer
45 views

Could electric dipoles within hadrons provide an alternate explanation for strong force? [closed]

We all know that hadrons such as proton and neutrons are made up of quarks and not all of the quarks have the same charge. This would suggest that they have a positive and negative side. In the case ...
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Electric field due to a hydrogen atom

Electric field due to two opposite charges According to the answers in the previous questions, if you separate the two charges from each other, they will produce a non-zero electric field ...
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Magnetic Dipole Moments and Dipole Contributions

I'm currently in Physics 2 (calc-based) at my University. On the last exam we had questions over magnetic dipole moments and dipole contributions. I'm still unable to solve these problems. Would ...
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22 views

Vector components for the dipole of water

I was looking online for the components for the dipole moment vector of water in the molecular frame. Does anyone know what the values would be for $\mu_x$, $\mu_y$ and $\mu_z$ for a water molecule in ...
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1answer
103 views

Collective dipole oscillation and specular reflection

Let's say I shine light upon a surface and observe a specular reflection. If I look with a electron microscope, I see tiny particles much smaller than the wavelength of light (~10 nm) and also closely ...
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Dipole moment in a bulk crystal

When calculating the dipole moment in a crystal, there is always one term neglected. This neglection is never discussed and I do not understand it at all. Assuming the Bloch functions $\Psi_{n,\vec{k}...
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What is the nature of the multipoles used to shape/re-direct an e-beam?

Imagine having an electron beam, just like in an electron microscope. Now imagine that we have some multipoles prepared in the beams path to influence the shape/path of the beam. My question is: ...
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11 views

Taking out % contribution of a zero order state from an eigenvector - dipole calculation

I am doing an analysis of a theoretical spectroscopy calculation. I take an eigenvector (nx1) and dot it with many zero-order dipole vectors (nx3) to get the dipole contribution to my new eigenstate. ...
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1answer
112 views

Is a Microwave oven without a faraday cage a health hazard?

Microwave ovens have something of a Faraday-cage/shield to keep from leaking (emitting) EM radiation. What would happen if the shield or the door was removed? No doubt it would be less efficient as ...

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