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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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Electric motors and change in flux

"When a current passes through an electric motor, the magnetic force on the motor causes a torque on the loop of wire causing it to turn". However, when the loop rotates, there should also be a ...
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Ferromagnets and magnets tend to align in the center. Why is that?

When you bring a large iron plate and a magnet, the magnet attracts the iron plate and it tends to slide itself to the center. When I place it on the edge, it always aligns at the center why is that?
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Can (quantum) angular momentum $L$ be zero?

I am trying to calculate the orbital magnetic moment, $\bar{\mu}$, for Sodium, which has an electron configuration of $1s^2 2s^2 2p^6 3s^1$. The full shells do not contribute to $\bar{L}$ and $\bar{S}$...
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What is the difference between diamagnetism and superconductivity?

Basically, What is the difference diamagnetism and superconductivity? As far as I understand, diamagnetism comes from the fact, that all electrons in a solid, when exerted by an external magnetic ...
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Contradicting forces on a circular loop under current in magnetic field?

I have the following general conceptual concern. Think of a thin conducting loop of radius $R$ placed in the $x$-$y$-plane at $z=0$. There is a homogeneous current density $\vec{j}$ running through ...
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Faradays law for a falling magnet

If experimentally it can be proven that the velocity of a falling magnet through a coil is proportional to the emf induced, has it also been proven that dB/dt is proportional to the emf induced and ...
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Curie temperature and magnetization?

If an ferromagnetic object is heated and reaches Tc the magnetization gradually drops as we get closer to Tc or it's a instant drop? Can I assume as I heat the object, the magnetization is weakening ...
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Determining the location of magnetic moments

The magnetic moment of a closed current loop is $$\mathbf{m} = \frac{I}{2}\int\mathbf{r}\times d\mathbf{r}.$$ Note that $\mathbf{m}$ is independent of any coordinate frame. How, then, does one ...
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How to calculate the magnetic dipole moment of a bar magnet?

I want to calculate the force between two magnets. In a previous Phys.SE question, I was told that I needed to use the dipole-dipole interaction, but that equation depends on $m$, the magnetic dipole ...
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does the current's direction on a loop with a magnetic field affect the torque?

I have a question in my book The question is very easy, but then my solutions manual gave me unexpected answers I don't get how in d) they conclude the vectors go in the opposite direction, but in b)...
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Is there energy stored when iron is magnetized?

When a piece of iron is magnetized, and the domains are aligned, Is there energy stored? If so, how much energy is stored? If there is an attraction between that same iron and the source of the ...
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Can I Demagnetize a ferromagnet with a hammer?

If an iron is exposed to an external magnetic field, the iron's domains are all aligned with that ext-B . If I strike it with a hammer, will it be demagnetized? Comparing it with heat, I know the Tc ...
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Will a ferromagnet retain its magnetic properties after reaching the curie point?

If a piece of iron or any kind of ferromagnet reaches its Tc, it will lose all it's magnetic properties, and will not be affected by an external magnetic field, if it drops back to room temperature or ...
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$E\times B$ drift of a single particle in vacuum with unifiorm $E$ and $B$

The force on a charged particle in electric field $E$ and magnetic field $B$ is given by: \begin{equation} m \dot{v} = q ( E + v \times B) \end{equation} Then, the $E \times B$ drift velocity $v_E$ ...
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Magnetic moment and other invariants of Lorentz System

It's a standard fact that the quantity $\mu = v_{\perp}^{2}/B$ is approximately conserved in the system $d_{t}\mathbf{v} = \gamma (\mathbf{v}\times\mathbf{B})$. The paper Magnetic Moment to Second ...
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What are correlated magnetic moments?

My book has the following sentence and I don't understand what correlation or lack of correlation means: At high temperature the magnetic moments of adjacent atoms are uncorrelated (to maximize ...
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Magnetic moment of electron

Since magnetic moment come from the circulation of charge, what is the origination of the electron's magnetic moment? Because spin of electron is not the classical spin of particle. Can we say that ...
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Magnetic moment precession around magnetic field

I have a question regarding the magnetic moment of an atom. If you just have one atom, and you apply an external magnetic field in lets say the z-direction. Then the magnetic moment will precess ...
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Sliding force less or equal?

Why is the force required to slide a magnet off a steel plate A LOT less than the force required to directly pull it off? The force required to pull the magnet can be: 20lb While the force required ...
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How to derive magnetic moment for integrated circuit level?

Imagine we have a circuit on the xy-plane, with a random geometry (it just need to be closed). I want to calculate the magnetic moment of this setup: $$\vec{m} = \frac{1}{2} \int_V d^3 x' \vec{x}' \...
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Field At Magnetic Dipole

Suppose I have a pure magnetic dipole $\mathbf{\vec m} = m\hat z$ located at the origin. What is the magnitude of the field $|\vec B|$ as $r\to 0$? In other words, what is $\lim_{r\to 0}\frac{\hat{r}\...
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Why are the magnetic moment and the angular moment related?

Why are the magnetic moment and the angular moment related? I've always read everywhere that they are related but found nowhere a satisfactory explanation of the cause
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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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In what direction does a frustrated magnetic moment get aligned?

Consider 3 layers of Ferromagnetic materials stacked on top of each other with appropriate spacer layers in between. Let the top and bottom layers be pinned to layers of Anti Ferromagnets adjacent to ...
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Nuclear Magnetic Resonance (NMR) Conceptual Questions

Let $M$ be the magnetic moment of a system. Below are the Bloch equations, including the relaxation terms. $$\frac{\partial M_x}{\partial t}=({\bf M} \times \gamma {\bf H_0})_x-\frac{M_x}{T_2} $$ $$...
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What name would you give to the method of approximating an arbitrary magnet with many smaller dipoles?

Let's say I had an arbitrarily shaped permanent magnet, with total magnetic moment $M_{0}$. Ways to calculate the magnetic field of this magnet include an analytic solution (if one exists), as well ...
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Why don't alpha particles have magnetic moments?

As I understand, particles such as the neutron, whilst having no external charge still possess a magnetic moment due to the underlying charges of its components. By that logic why does the alpha ...
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Force on a bar magnet

A bar magnet is freely falling vertically inside a conducting ring placed in horizontal plane. Will it fall with an acceleration equal to g, less than g or greater than g?
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What is the Landé g factor?

What is the Landé g factor? I know that it gives the relation between magnetic moment and angular moment, but i wanted to know why are those magnitudes related to each other and why is the magnetic ...
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What's the difference between exchange spin wave and magnetostatic spin wave?

So far I've heard of three kinds of spin waves Magnetostatic spin waves (MSW) Dipole-exchange spin waves (DESW) Exchange spin waves (ESW) What's the difference?
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Is it possible to create only a magnetic wave?

I want to know if its possible to create only a magnetic field,which i can direct to a certain chosen object?
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Do magnetic field shift away from the coil that generates it?

I read about magnetic induction communication on Lockheed Martin's wireless mining communication system In this interview Warren Gross said: We generate a signal and send it through a loop that's ...
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How do magnets work?

I've read a classbook on the field theory (including EM): it perfectly describes quantitive patterns in EM-theory, but I have no luck understanding how and why it works. I mean, magnetic substances ...
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Relationship between nuclear spin and nuclear magnetic moment?

We know that nuclear magnetic moment can be expressed in terms of the expected value for nuclear spin as: $$\langle\mu\rangle =[g_lj+(g_s-g_l)\langle s_z\rangle]\frac{\mu_N}{\hbar}$$ (Cf. Krane), ...
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Thought experiment with entangled electrons

Suppose we start out by having two entangled electrons. We separate them by some distance and we put one electron inside a thin loop of wire connected to an extremely sensitive voltage measuring ...
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Can magnetic fields be redirected and focused at one point?

I know that magnetic fields can be redirected, but... given a situation where you have static magnetic field over a large area, and you want to quickly change the magnetic field strength. Is it ...
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How to find the poles on a spherical magnet?

To any nonmagnet, the whole sphere is a magnet. To another spherical magnet though, there is a rough area on the surface where it is strongly repelled. Given a spherical magnet, how should the poles ...
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Experimental evidence showing the kinetic energy of an electron changes in a static non-uniform magnetic field?

In a previous question, Does a magnetic field do work on an intrinsic magnetic dipole?, one highly rated answer suggested that static magnetic fields do work on intrinsic magnetic dipoles in a non-...
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QM interpretation of Larmor precession

Typically when I think of a spin moment in an external field, I visualize it classically in terms of a magnetic moment precessing around the external field vector. Now how is this described quantum ...
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What is the electric field generated by a spinning magnet?

Consider a cylinder of permanently magnetized material, with uniform magnetization pointing along the cylindrical symmetry axis (the $z$-direction). The magnet is rotating about its cylindrical ...
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Magnetic moment of relativistic rotating ring

Let's consider rotating charged ring. Theoretically mass of this ring has no limit as rotation speed increases. So what about magnetic moment of the ring? Is it limited by the value of speed of light?...