Questions tagged [dipole]

Use this tag for questions regarding electric or magnetic dipoles, meaning a field on an object with a north and south pole or two point charges of equal magnitude.

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Dipole term in light-matter interaction

I have a question regarding the description of the term “dipole” in light-matter interactions. If I understand it correctly, there are 3 different things that one can declare as a dipole during light-...
1 vote
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Dipole antennas and the $B$ field

A dipole antenna responds to the electric component of a EM wave. Does the magnetic component of a EM wave have any effect on the performance of a receiving dipole antenna?
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How to go from a vector operator to its components?

(I'm sorry if this question is a duplicate, I couldn't find anything that answered my question.) I'm doing an exercise where I'm supposed to get the matrix elements for the vector operator $D$ (the ...
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Linear approximation of the magnetic dipole field

Summary: using 3 angles to represent a magnetic dipole's orientation is redundant because the rotation around the $z$-axis of the dipole does not change the magnetic field, there are only 2 DOFs for ...
1 vote
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Can we relate the dipole force on a two level atom to the AC stark shift it experiences?

Consider a two level atom, with ground state $|g\rangle$ and excited state $|e\rangle$. In the rotating frame, the dynamics of the two level atom interacting with radiation detuned by $\Delta$, and ...
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Orientation of Magnetic Induction of a Dipole Source in MEG

I am working with source-reconstructed MEG data, and what I would like to know is that when we obtain the magnetic induction (using the right-hand thumb rule) of a dipole source, is it only the ...
226 views

Dipoles as vectors

A triatomic molecule $X_2Y$ has plane structure as shown in figure. Due to difference in electronegativity, charge acquired by each X atom is $q$ and charge on Y atom is $- 2q$. The bond length ...
1 vote
66 views

Potential of an electric dipole

I'm currently working my way through Griffith's Introduction to Electrodynamics (4th ed). In chapter 3 section 4, he shows that we can take the equation for the electric potential of a continuous ...
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Dipole moment in an electric system when the charges are not symmetrically distributed

Suppose we have two -q charges and +2q charge ate the corners of an equilateral triangle. Now to calculate the dipole moment suppose we assume that the +2q charge is 2 charges of +q magnitude. My ...
1 vote
96 views

Electromagnetic field of dipole antenna

Why do dipole antennas generate EM waves by alternating electric fields instead of alternating magnetic fields? Why don't alternating magnetic poles detach the magnetic field like how it can do so ...
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1 vote
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Minimum frequency for a dipole antenna to work

Does a dipole antenna need a minimum frequency of AC to make the electric field detach and propagate?
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Dielectric and dipole

When a molecule of a dielectric material is placed in an electric field, the molecule acquires an electric dipole moment. Why?
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Equation relating the current carried by a solenoid to the force experienced by a magnetic dipole?

I am trying to find an equation or a series of equations that relates the current I carried by a solenoid of length L with turns N to the force F experienced by a magnetic dipole of strength M that ...
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Entropy of dielectric in Capacitor?

So I am learning about dielectrics, and my professor was saying that if we connect capacitor containing dielectric to a DC source, theoretically it should produce little to no heat (the only heat ...
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Coexistence of a static electric and magnetic dipole

I have been trying to construct a charged object (not a conductor carrying any current) that can behave simultaneously as an electric and magnetic dipole and then calculate the electric and magnetic ...
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Decay rates, time-energy uncertainty, and photon spectrum in two-level system

This question concerns mainly a few statements from the following article https://journals.aps.org/pra/abstract/10.1103/PhysRevA.94.063839. It states: "Early studies of two-level quantum systems ...
1 vote
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Potential energy of an electric dipole without any external field

What is potential energy of an electric dipole without any external field? If its 0 then why? Wouldn't the charges get attracted thus do work so they must have some potential energy.
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1 vote
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Can static electricity (charged balloon) attract any liquid other than water?

I know that a charged balloon can attract a stream of water, because it is a dipole. I am wondering if a charged balloon can attract any other liquid other than water? Does it have to be a dipole? ...
1 vote
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How can you understand curl of electric field illustratively?

Considering the curl of the electric field of an electric dipole, this will be zero in absence of magnetic effects which is clear to me. I watched a video by 3Blue1Brown (some time ago) who explained ...
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How does an antenna work?

I'm looking for a model of an antenna that would explain how it works an in particular where the values of impedance like 36.5 ohms come from. I've tried looking but everything i found was overly ...
1 vote
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Why does an oscillating charge emulate an oscillating dipole in the far field limit?

I understand Thomson scattering as: When an EM wave is incident upon a charge causes it to oscillate in turn releasing energy as another electromagnetic wave. In an Electrodynamics lecture we took a ...
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Dipole Antenna: Electromagnetic Wave

I have read about wave propagation and dipole antennas here. I do not understand how a single electromagnetic wave (i.e. the electric field in particular - I can come up with the magnetic field later) ...
734 views

Modeling a pure dipole as a function similar to a Dirac delta function

I am taking an undergraduate course in E&M following Griffiths. I was wondering if there is a good way to embed the information of a dipole into the charge distribution (and if it would be of any ...
1 vote
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Energy conservation in dipole capacitor interactions

If we bring a separable dipole (say a single ammonium chloride molecule) from infinity to the center of a capacitor, once the dipole stabilizes and the rotational energy is lost to electromagnetic ...
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Wave Propagation: Dipole Antenna

I was watching the following video here. This video explains the following image below represents an electric field generated from a dipole antenna. How does a single wave of electromagnetic radiation ...
1 vote
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Hertzian Dipole: Why is there no longer a phase shift at $\frac\lambda2$? [closed]

Today we learned about the Hertzian Dipole. Out teacher told us that the length of the wire connecting the two capacitor plates is $l=\frac\lambda2$. He also stated that there is a no more phase shift ...
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Attractive or repulsive force between two statically charges plates [duplicate]

So I'm trying to calculate some mechanics for an electrostatic attraction/repulsion system and I want to make sure that I'm using the correct numbers. I did a bunch of research on my own and I think I ...
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Derivation for Quantum optics dipole radiation formula

An often used formula for the radiation field of a dipole is the following one: \begin{align} \vec{E}(t, \vec{x}) = \frac{1}{4 \pi x^3} ( 3 \hat{x} [ \hat{x} \vec{d}(t_r)] - \vec{d}(t_r) ) + \frac{1}{...
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What is the interpretation of the matrix elements of a second order perturbation capturing dipole-dipole interactions between two molecules?

The system I am studying is one molecule comes in close proximity with another molecule, and we are interested in calculating the energy of the resulting induced dipole-dipole interactions. I want to ...
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1 vote
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$\vec{E}$-field in toroidal polarized dielectric

In an electrostatic situation, imagine a dielectric torus that is permanently polarized with polarization given by: $\vec{P} = P(r, z) \hat{\phi}$ (Here cylindrical coordinates are used with the $z$-...
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Different derivations of dieletric polarization charges in Griffiths and Feynman

I am reading Griffiths's Introduction to Electrodynamics (3rd edition). In the part of dieletric polarization (p.166), the author first adopts the potential for a single dipole: V(\mathbf r)=\frac{1}...
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Meaning of electric dipole moment

what is the meaning of electric dipole moment? Or why do we need to define electric dipole moment?
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Multipole expansion, same charges

I know dipole is defined with 2 opposite charges. That's why in EM dipoles exist, while in gravity they do not. However, I view multipole expansion as a way to describe how the distribution of charges ...
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Understanding polarization and magnetization intuitively?

I am trying to develop a more intuitive understanding of the field produced by magnetization and polarization. I have the following image, and I can derive it from Maxwell's equations what the fields ...
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Computation of the Force acting on an electric dipole [closed]

I’m having trouble computing the force on an electric dipole. I will simplify the problem so that I can only post the problematic part. There is a point charge $q$ at the origin of our Cartesian ...
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Dipole approximation

I am studying the "dipole approximation" as is defined in quantum optics. (See, for example Introductory Quantum Optics by Gerry and Knight, pages 24–25.) In this situation, we have the ...
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Why do the nucleons interact via strong force even though they are color neutral?

Particles that transform non-trivially under color $SU(3)$ interact via strong nuclear force. However, neutrons and protons, despite being color singlets, interact via the strong force. How do we ...
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1 vote
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What does centre of mass of charge mean?

I am unable to understand what does this centre of mass of positive charge and centre of mass of negative charge mean??