# Questions tagged [dipole]

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49 views

### 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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### 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 ...
1 vote
55 views

### $\vec{E}$-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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### Potential energy of an (electric) dipole is said to be zero when the angle it makes with the applied uniform field is zero yet it experiences torque

My doubt is that I am unable to understand why a dipole would continue to experience a torque due to a field eventhough the potential energy is zero for angle 90⁰ it makes with the field.Like,there is ...
63 views

### Does this basic example of two bar magnets preserve angular momentum conservation?

Let's say I hold two bar magnets side by side both vertically aligned ($z$-axis). I don't want to worry about their shapes, so let's approximate them as dipoles. I will use the dipole formula rather ...
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### Why equipotential surface for an electric dipole is concentric oval shells around the opposite charges?

Why equipotential surface for an electric dipole is concentric oval shells around the opposite charges? Please explain.
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### Electric Field Lines - Why do we draw such lines for dipole?

In a dipole case (1 proton / 1 electron), we draw $E$ field lines such as they go and move into the negative charge. If we take an example point near negative charge's upside vertically, we see there ...
41 views

### Why is the magnetic field due to a dipole at equatorial position opposite to the magnetic moment?

I understand that the direction of the magnetic field lines at the equatorial plane is opposite to the direction of the magnetic moment by definition. Is there a reason of physical significance as to ...
19 views

### Why in an isotropic, linear and homogeneous dielectric, the average electric moment can be expanded as a series of electric field $\mathbf{E}$? [duplicate]

As I was reading this classic 1939 document by Kirkwood The Dielectric Polarization of Polar Liquids. It is stated in the text that the average electric moment in an isotropic liquid can be expanded ...
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### How does a positive charge's electric field lines loop back to negative charge?

In this video about electric dipoles, at 6:14, the speaker mentions that all of the red lines will loop back into negative (blue) charge, but I don't see how this is possible. Specifically, he gives ...
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### What's the relative phase between current, voltage and electric field in a receiving dipole antenna?

To help keep the question simple, please assume a half wavelength dipole at resonance such as in the image below: I have been thinking about this problem using the analogy of a harmonic oscillator: ...
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### Oscillating dipole, longitudinal Electric field oscillation?

Assuming the presence of a dipole consisting of two oscillating point-like charged particles on the z axis. Lets say whose motion follows $q_{\pm}=\pm 1\pm \frac{1}{2}\cos(\omega t)$, it is a well ...
81 views

### How and why potential energy is stored in a dipole in uniform electric field?

I learnt that potential energy is stored in a dipole in uniform electric field when it is rotated from theta = pi/2 to any other theta, and the magnitude of stored potential energy can be found out by ...
173 views

### The force on a magnetic dipole in a non-uniform magnetic field

Let's say there is a non-uniform magnetic field $B=(0,0,z)$ (i.e. the field is parallel to $z$-axis and the amplitude is linearly changing along $z$-axis). If there is a current loop (=magnetic dipole)...
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### Is potential enough to determine dipole distribution?

I was working on a problem and I had to mathematically distinguish a charge and its distribution from a dipole and its distribution in the space. Following is an example where I am confused how to ...
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### Issue in justifying the use of dipole potential in the calculation of bound charges in a dielectric

We have a polarised material, suppose. The goal, is to find the bound charges. DJ Griffiths (4th ed, section 2.1, page 173) "chops" the material into smaller infinitesimal chunks and writes: ...
124 views

### How is a dipole stable?

So I was reading about dipoles, two charged particles of opposite charges a very small distance from each other. But if the particles have opposite charges, shouldn't they attract and crash into each ...
142 views

### Electric field of dipole antenna

I have seen that the electric field of a dipole antenna detaches and propagates. For a section of the detached electric field, will the antenna experience recoil if the detached field moves a charged ...
101 views

### How do I renconcile electric potential and field of a dipole along its perpendicular bisector?

It's been a while since I've studied electrostatics and is my first time posting here, so please forgive me if I'm missing something basic. According to my reference book, the electric potential of a ...
58 views

### Classical dipole-dipole interaction in iron

I've been reading about the classical magnetic dipole-dipole interaction and I'm wondering how it would work in a ferromagnet element like iron (theoretically under the assumptions I will write below)....
39 views

### Optical matrix element in graphene: is electron $k$ perpendicular to $E$?

I faced some problems with understanding the process of light absorption in 2D (e.g. graphene). Suppose we have Dirac graphene hamiltonian, skipping all numerical factors:  H = \hbar v\begin{pmatrix}...
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### What is the secret behind the striking similarity between a quark pair and a bar magnet?

If one tries to split a pair of quark and an anti quark, one ends up with two pairs, in the same way, when one tries to break a magnet in half, one end up in the same way with two magnets, so is this ...
1 vote