Questions tagged [magnetic-moment]

The magnetic moment of a magnet is a quantity that determines the force that the magnet can exert on electric currents and the torque that a magnetic field will exert on it. A loop of electric current, a bar magnet, an electron, a molecule, and a planet all have magnetic moments.

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Magnetic dipole moment due to folded loop [closed]

A steady current i flows in a small square loop of wire of side L in a horizontal plane. The loop is now folded about its middle such that half of it lies in a vertical plane. Let $ μ_1 $ and $ μ_2 $ ...
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Is it better to spread the coil to maximize magnetic strength in air gap of a C shape iron core

See the 2 example below of a C shape Iron Core 99.8% iron. in both cases, assume that: the wire length is the same, say 1000 feet of copper wire. The amp being used is the same The N turns are the ...
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How to calculate Tesla value at the end of a solenoid when iron surface expands?

assumptions: The core and top cylinder are made of pure iron 99.8% with a permeability ( µ ). To calculate the Tesla value at point B (at then end of the solenoid), we use: $$B =\frac{\mu\cdot N\cdot ...
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Is it right assume the greater the precession of a type of particle in the same magnetic field the slower the particle spin?

Is it right that the greater the Larmor frequency of a particle measured for same magnetic field applied the slower a particle spin is? I read these articles http://hyperphysics.phy-astr.gsu.edu/hbase/...
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Satisfying and puzzling phenomenon about magnetic dipole

I just found a cool video of magnet falling through cooper pipe. So I naturally have a couple of questions about this physics phenomenon. I even tried to derive the equations of motion... During my ...
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Investigation with magnets

Take the following method for an experiment with magnets. Method: Hold the magnet about 1 m above the desk Place a paperclip at the end. Add another paperclip until the chain cannot hold any more ...
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What $\mu$ represents in Gryzinski's free fall atomic model equation?

When you look into the Gryzinski's atomic free fall model equation (see wiki link here ), it has a variable $\mu$. What it is? $L = \frac{1}{2} m v^2 + \frac{Ze^2}{r}+\frac{Ze}{c}[v\cdot\frac{\vec{\mu}...
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Why armature is being rotated in DC generator?

I am wondering about why armatures are being rotated instead of being static? The magnetic flux will still cut the armature windings and because of this induced current will be generated. So, why it ...
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Permanent magnets - why spontaneous symmetry breaking?

I am not a physicist. I'm curious about the cause of permanent magnetism in ferromagnetic materials. So far, I have formed the impression that a macroscopic net magnetic dipole moment is formed from ...
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Do Protons and electrons actually have magnetic poles?

From what I’ve read protons and electrons only are attracted to each other because they have opposite electric charges. What I don’t understand, though is that I’ve also read that both protons and ...
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How does QM explain the proton's magnetic moment?

I read that QM is baffled by the proton's angular momentum, I don't know if the issues are related, but do you know if and how it explains the odd value of the magnetic moment of the proton and of the ...
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Hamiltonian of an electron in a magnetic field

Suppose I have an electron in a magnetic field given by: $$\vec{B}=B\hat{z}$$ The potential energy of this system is given by: $$U=-\vec{\mu} \cdot \vec{B}=\frac{g\mu_B}{\hbar}\vec{S} \cdot \vec{B}$$ ...
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Repulsive Force between two cuboidal magnets

I have 2 cuboidal permanent magnets(same grade) which are kept a small distance apart. They are kept such that they will repel each other. How do I calculate the force of repulsion between them? I ...
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How do I show mathematically that net intrinsic magnetic moment of a substance is $0$?

The following argument is made, keeping in mind the classical theory of diamagnetism. I'm not including the correct quantum mechanical theory in this question. Consider a material in the absence of ...
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Goodenough-Kanamori rules

Could anyone elaborate more on Goodenough-Kanamori rules or guide me to the right textbook for this? For example, the Goodenough-Kanamori rule predicts a ferromagnetic interaction between d5 with t2g3 ...
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Ferromagntism and Canting Moment from Antiferromagnetism

There is a thin-film sample that shows a ferromagnetic-like hysteresis loop, but the bulk material is known to be an antiferromagnetic material with small canting, and the canting moment will make the ...
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Why does magnetic dipole's north pole pointing in the direction of magnetic field increases overall magnetic field?

I'm studying magnetic moment- current loop, electron/proton/charge revolving, magnetic dipole etc. This is about paramagnetism of materials. According to me magnetic dipole's south pole is attracted ...
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How to reduce magnetic field between two magnetic shield sheets (silicon steel sheets)?

I put 2 parallel silicon steel sheets between magnetic field as below: As silicon steel has much bigger permeability than air,magnetic line will go through 2 silicon steel sheets. What I can do to ...
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Why $ \vec \mu$ is induced by $\vec B_{ext}$?

I have read that in the presence of an external magnetic field $\vec B_{ext}$ the magnetic moment induced on a paramagnetic ion is $\vec \mu=g \mu_B \vec J$ where $g$ is the Landé g-factor. Why is $\...
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Is it possible to introduce magnetic monopoles without breaking $∇ · B = 0$?

In another word, the net magnetic charge is always zero everywhere, which means magnetic field is still strictly source free. On the other hand, the net magnetic current jm can be nonzero, which means ...
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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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Is there an analogous potential for magnetic moments in comparison to that of electric dipoles: $\frac{k \vec{p}\cdot \hat r}{r^2}$?

If I am not mistaken the electric potential of an electric dipole is given by: $$ V(r) = \frac{k | \vec{p}|\cos \theta}{r^2} = \frac{k \vec{p}\cdot \hat r}{r^2} $$ Where $\vec{p}$ is the electric ...
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Maximum $B$-field at the surface of a permanent magnet

I have the dipole formula for a permanent spherical magnet in coordinate-free form. $\vec{B}=\frac{\mu_{0}}{4\pi}\frac{3(\vec{m}\cdot\hat{r})\hat{r}-\vec{m}}{r^{3}}$ I am trying to find the maximum $B$...
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Why is the Anomalous magnetic dipole moment defined as half the extra contribution to the $g$-factor?

Was there a reason Julian Schwinger or Richard Feynman officially defined the anomalous magnetic moment as half of the extra $g$-factor? $$ a = \frac{g-2}{2} $$ (equation is from the Wikipedia article ...
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Magnetic moment of current loop

From what I have learnt, the magnetic moment of a current carrying loop is $$\pmb{\mu} = NI \mathbf{A}.$$ But what is written in this book Modern atomic and nuclear physics by Fuzia Yang, I am not ...
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Quantum physics notation in statistical physics

Studying statistical physics, in particular studying paramagnets and ferromagnets, I found some quantum mechanical formulas that I don't understand how to interpret. I don't understand if they are ...
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Deriving the magnetic field due to a dipole

I am trying to follow along with a derivation from Cullity, Introduction to magnetic materials 2011. I am getting stuck at a very early stage when computing the components of the magnetic field at a ...
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Can fundamental particles have magnetic/electric quadrupoles, octopoles, and higher-order moments?

Fundamental particles come with magnetic and electric charge, which makes the particles into a monopole source for the magnetic and electric fields. Of course, the magnetic charge is zero for all ...
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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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What is the value of the SPIN magnetic moment of a proton?

If I understand it correctly the anomalously large total magnetic moment of the proton inside the nucleus of the atom is because it is a combinatoric particle and there are contributions by the quarks'...
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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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Is the spin quantum number conserved during a spin flip in the Kiatev honeycomb model?

It seems that a spin flip in Kitaev honeycomb model gives an itinerant Majorana fermion and a pair of $\pi$ fluxes. Because a spin flip causes $\Delta S = 1$ and $S = 1/2$ for Majorana fermion, does ...
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On rotating magnetic charges

Consider a sphere with magnetic charge $P$ and electric charge $Q$. We know that when the sphere is subjected to rotation about the $z$-axis, there is a magnetic dipole moment generated from the ...
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Why do diamagnetic rods align perpendicular to the field?

My textbook says that Diamagnetic substances align their longest axis perpendicular to the field in uniform magnetic field while paramagnetic substances align their longest axis parallel to the field. ...
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How the force on magnetic charges are introduced with magnetization field?

In the most text books used in Japanese highschools, $H$ field is introduced for magnetic field before $B$ field (flux density) is introduced. The definition in the textbooks is as follow: When a ...
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Magnetic Flux Density in Matter

I'm working on a magnetostatic problem. I want to magnetize iron-oxide nanoparticles. I want to simulate the magnetization of said particles which depends on the magnetic flux density. Since the ...
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How to experimentally determine the relation between magnetic moment and spin angular momentum of a quantum particle?

In quantum mechanics the spin magnetic moment in terms of angular momentum is given by $\mu=g\frac{e}{2m}L$, where $g≈2$ Now the question I was wondering, how do you determine this with experiments? I ...
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Are permanent magnets ferromagnetic?

It is written on wiki that "Permanent magnets are made from "hard" ferromagnetic materials..." Should I conclude from it that they are ferromagnetic? For its not written that they ...
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How to find the magnetization of a neodymium magnet?

I am interested in knowing how to find the value for Magnetisation of cylindrical N35 neodymium magnets based on the information sheet, or through the means of an experiment. this is to calculate its ...
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Anomalous magnetic moment form factor of $e^-,\mu^-$ and $\tau^-$ in QED

The anomalous magnetic moment form factor $F(q^2)$ of an elementary fermion at $q^2=0$, calculated at one-loop, is $$F_2(0)=\frac{\alpha}{2\pi}.$$ At least at this order (order-$\alpha$), $F_2(0)$ ...
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Physical meaning of the form factors $F_1(q^2)$ and $F_2(q^2)$ for $q^2\neq 0$

The charge form factor $F_1(q^2)$ and the anomalous magnetic moment form factor $F_2(q^2)$ have clear interpretations at the value $q^2=0$ i.e. $F_1(0)$ is equal to the charge of the electron and $F_2(...
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How to calculate the expression for magnetic field at a position $\bf r$ based on the formula for a cylindrical magnet?

this picture is taken from "Testing a simple model for the magnetic cannon, Grigorios Magkos*, Bekari Gabritchidze and Kokkimidis Patatoukos". How should I use this to find the magnetic ...
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How to undertstand the shape of $t_{2g}$ orbital $|xy⟩\pm i|yz⟩$?

It is well defined that under the crystal field splitting, d orbital will be splitted to $e_{g}$ and $t_{2g}$ orbital. By choosing the basis as the linear combiantion of real basis, $t_{2g}$ orbital ...
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Expression for external magnetic field of a cylindrical bar magnet?

I would like to calculate the magnetic force of a cylindrical bar magnet on a steel ball bearing, which is a distance away in a straight line from one of its poles. What is the expression for this? ...
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How to obtain the torque from a magnetic moment Lagrangian?

Consider a body with magnetic dipole moment $\vec m$ subject to a magnetic field $\vec B$. We know that the torque on the body will be given by: \begin{equation} \vec \tau = \vec m \wedge \vec B \end{...
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Why don't we use earth's magnetic field to desaturate the reaction wheels of satellites?

While reading about the James Webb Telescope I learned that the sun's radiation pressure exerts a torque on Webb's big sunshield that needs to be countered by reaction wheels. Every once in a while, ...
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Conceptual explanation of Bulk Magnetization arising from atomic magnetization

I am reading about chemistry and NMR. Atoms with uneven number of protons/neutrons are magnetic, and susceptible to magnetic fields. In NMR, a sample is placed into a constant magnetic field. This ...
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Field At Point Due to Paramagnetic Material in External Field

TL;DR: How do you calculate the field at a given point when both an external field and a paramagnetic material are present? My overarching question has to do with the effect an induced magnetization (...
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Relationship between electron $g$ value and fine structure constant from QED

The wiki article on the fine structure constant says that 'The theory of QED predicts a relationship between the dimensionless magnetic moment of the electron and the fine-structure constant $\alpha$' ...
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Magnetization in Paramagnetism

I have a question regarding the magnetization of an object. Let's say this object has magnetic moments pointing in random directions, such that the total magnetization is null. If we apply an external ...
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