# Tagged Questions

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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### Motion of charged particle in uniform magnetic field

To create a uniform magnetic field I took a current carrying solenoid connected to a battery, then I took a long straight wire connected to another battery, the wire passes from inside the solenoid. ...
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### Magnetic force and torque for 2D neodymium ball simulator

I'm trying to write a simulator for neoballs. I'm doing only 2D for a start, in which each ball has a magnetic moment, m, that is in the x-y plane. The simulator will use time-step integration at 60 ...
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### Magnetization and magnetic moment

If a current carrying loop has magnetic moment m, how can i determine the magnetization M, of it? Ive done some reading and have found a formula that seems to solve it, it says that M is equal to the ...
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### Permanent Magnet Lines & Currents:

A permanent magnet produces lines of magnet flux that we call a "magnetic field". Those lines come from inside the magnet, come out of the N pole, loop outside the magnet, & return back into the ...
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### Why toroid has no magnetic pole?

Our teacher taught us about Gauss law of magnetism, $\phi_B=\oint_s{\small{}}\vec {B} .\vec {ds}=0$(being valid because magnetic field line form closed loop, right?) which denies the existence of ...
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### Why can't weak core-less electromagnets be used in conjunction with strong permanent magnets to perpetually harvest energy?

Why can't weak core-less electromagnets be used in conjunction with strong permanent magnets to perpetually harvest energy? Magnets will attract ferrous materials but some materials like copper or ...
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### Repelling a weak permanent magnet with an electromagnet

I have a question about magnetic repulsion. Suppose I have a permanent magnet (axially magnetized) placed on top of the iron core of an electromagnet. I want to switch on the elctromagnet to repel the ...
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### How do the magnetic moments of protons and neutrons effect the total magnetic moments of atoms?

I've heard that magnetic properties of atoms are mostly determined by the presence or absence of electrons with unpaired spin. The proton has a magnetic moment of $1.4 \times 10^{-26} J/T$ and the ...
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### Why objects with magnetic dipole moment sometimes orient towards external B and other times they do precession?

Given the magnetic dipole moment in external uniform magnetic field $\vec{B}$, I am trying to understand why sometimes $\vec{\mu}$ simply aligns with the $\vec{B}$ and stays that way, while other ...
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### How to calculate the force between two magnetic dipoles as a function of distance [duplicate]

Is there a generic equation to calculate the force acting on two magnetic dipoles as a function of distance? For instance, two identical contacting, magnetite nanoparticles with known dipole, moving ...
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### Finding torque on a current carrying loop with respect to different points?

So how does the torque varies wrt different positions. Like if I'm trying to solve a question with a rod hanging with wires and a current carrying loop in between, how do i write the torque with ...
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### If I double the amount of oxygen molecules, do I double the paramagnetic force?

Oxygen is well known to be paramagnetic. If I take one molecule, $O_2$, and measure its paramagnetic force due to externally applied magnetic field, and then add another molecule near the first ...
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### Why don't the magnetic dipole moments in a neutron cancel out?

This may be a silly question. I thought magnetic dipoles were dependent on electric charge, so why in a neutron do the dipole moments not just cancel each other out?
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### Moving of spin up and spin down electrons in a magnetic field [closed]

Suppose we have an electron in a conducting space, and now we apply a magnetic field. Now according to the right hand rule, the electron will have a circular motion in the plane perpendicular to the ...
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### What is the physical significance of the Curie constant?

What is the physical significance of the Curie constant? I understand it depends on the effective moment of the ion and hence must be some measure of it, but what is it exactly? Like some average ...
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### Solving a step in the derivation of the anomalous magnetic moment of the electron

In the book An Introduction to Quantum Field Theory by Peskin and Schroeder there is a derivation of the anomalous magnetic moment of the electron. The Feynman diagram to be solved is this one: and ...
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### Relationship Between Magnetic Dipole Moment and Spin Angular Momentum

I am reading Introduction to Quantum Mechanics 1st edition by David J. Griffiths and I have a couple questions about this section on page 160. A spinning charged particle constitutes a magnetic ...
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### Is there an easy way to see that $\phi =\frac{\mu_0}{4\pi} \frac{\vec m \cdot \vec r}{r^3}$?

The scalar potential of an electric dipole is given by: $$\phi =\frac{1}{4\pi\epsilon_0} \frac{\vec p \cdot \vec r}{r^3}$$ The derivation of this is quick, however, is there an easy way to see that ...
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### Larmor precession and relaxation

I'm trying to wrap my head around Larmor precession and NMR pulses, but there's something that seems totally confusing and contradictory to me, and I haven't been able to find a definitive answer yet. ...
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### What is the magnetic quadrupole operator?

To find magnetic or electrical moments in quantum theory we must calculate the expectation value of an appropriate operator. The dipole operators are similar and are easy to find but I couldn't find ...
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### Thermal equilibrium - magnetization [closed]

The electronic ground state of neutral sodium atoms in a magnetic field splits into two no longer degenerate energy states. In the thermal equilibrium the occupation probability of the states is the ...
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### If $T_{kl}=\epsilon_{kil}m_i$, how to show $m_i=0.5\epsilon_{ilk}T_{lk}$? [closed]

In a book I am reading (about magnetic dipole), it is given that $T_{kl}=\epsilon_{kil}m_i$. Then, it says since $T_{kl}=-T_{lk}$, it can be shown that $m_i=0.5\epsilon_{ilk}T_{lk}$. I understand that ...
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### Microscopic interpretation of magnetization in a 2D electron gas

I'm studying the de Haas-Van Alphen (dHvA) effect in a 2D free electron gas, and I have a problem to interpret the microscopical meaning of the flip of magnetization during the dHvA oscillation. My ...
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### Magnetic moment of superconductors

How would a superconductor's magnetic moment be affected when it is placed in an increasing magnetic field? I know that as the magnetic field gets stronger, fluxons begin to penetrate into the ...
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### Explanation of absorption from Bloch Equation

Suppose in a magnetic resonance experiment the microwave/rf field is applied in x-direction.How to say that the component of magnetization which is out of phase with the microwave magnetic field leads ...
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### Why is a particles magnetic moment proportional to its spin?

the magnetic moment of a particles is given by, m=kS, where k is a constant the gyromagnetic ratio but where does this equation come from, is it just from experiments?
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### Can orbital angular momentum of an electron be changed?

In a lab at my university they are working on a project that deals with changing the "net magnetization" of a material by "flipping" the spins on some electrons. Is orbital angular momentum not ...
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### Net magnetic field & magnetization on a ferromagnetic material

A ferromagnetic materiel is saturated by an exterior magnetic field like so: Where $B_1$ is a uniform magnetic field. Then after some time $t$ another magnetic field $B_2$ is introduced as well, ...
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### Interaction between magnetic moments and magnetic field

Consider a particle with a magnetic moment $\vec{m}$. For simplicity, suppose that this particle is a circle in the plane $xy$ which can rotate around its center of mass along the $z$ axis. If this ...
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### Current loop and direction ambiguity of the magnetic moment

Consider a circular loop in the XY-plane which carries a current $I$. Then it behaves as a magnetic dipole with moment $\textbf{m}=I\int d\textbf{S}$ where $\int d\textbf{S}$ is the area of the loop ...
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### How is antiferromagnetism weakly attractive?

If all the electrons are aligned antiparallel to each other, shouldn't the magnetic susceptibility be 0? How can there be an attractive (albeit very weak) force?
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### How can an oscillating spin current in a nanostructure be observed or measured?

Through calculation it's predicted there's pure spin current oscillating in a nanostructure. Here by "pure" I mean the charge current is zero. One can imagine two electrons of opposite spin are moving ...
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### When do we have a coherent magnetization rotation? (single-domain particles)

So I am studying micromagnetics + spintronics and I am little bit confused with certain concepts regarding the physics of magnetic domains (especially single domain particles): What I already knew: ...
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### Magnetization of the source due to a stronger induced magnetic field?

Considering this classical diagram: From the top view, we can see a current carrying wire( flow of current is into the page) while an exterior magnetic field($B$) is applied perpendicular to it, ...
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### Total magnetic moment in an atom

I have a doubt regarding the calculation of total angular momentum of electron in an atom. Which is the right way to do it? Method 1: Total magnetic moment  \begin{align} \vec{\mu_J} &= \vec{...
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### How to Calculate the force between two different cylindrical magnets?

What happens to the formula when the two magnets aren't identical in height? One is a tiny neodymium magnet and the other is a longer electromagnet. Both are the same width but not height. Thank you
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### difference between magnetic dipole moment and torque on a magnetic dipole?

I am a bit confused. What is the difference between magnetic dipole moment and torque on a magnetic dipole ?