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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Distinguish a magnet from a non-magnet

Given two objects, one that is a permanent magnet and a "non-magnet" that is simply magnetizable, how would we determined which is which? Can this be done just by observing the motion they induce in ...
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Is it not necessary for electrons to move to create a magnetic field?

We have been taught about diamagnetism and paramagnetism on basis of the bohr's atomic model in our school. However, we know that electrons actually do not go in complete circles or tracks, they exist ...
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Energy of Magnetic Dipole

What is the total energy of a magnetic dipole, $\textbf{m}$, in the presence of a magnetic field $\textbf{H}_s$? I've seen the typical answer given is: $U = - \textbf{m}.\textbf{B}\Delta_v + U_s$ ...
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Schwinger's computation of anomalous magnetic moment of electron

I am trying to understand the details of the computation of the anomalous magnetic moment of electron (due to Schwinger). As far as I understand it reduces to study of an element of the $S$-matrix in ...
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Intuition of spin of photon [closed]

I read that intrinsic spin is a quantum property aka just a number, charged particle such as electron has magnetic dipole moment which can be detected using magnetic field like the Stern–Gerlach ...
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Is the boundary between ferromagnetism and paramagnetism well-defined?

I learnt that, when a ferromagnetic material is heated, it will become paramagnetic at a certain temperature. This temperature is called Curie point or Curie temperature. For example, Curie ...
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Why is the torque exerted by the magnetic field in a moving coil galvanometer independent of the angle of rotation?

How does an iron core cause the magnetic field to be constant and always perpendicular to the loop's moment in a galvanometer? The following image is from my textbook: Image source: NCERT Physics ...
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How accurate is the magnetic field determined by assuming a circular current carrying loop as a magnetic dipole?

I've learnt that a circular loop of area $A$ carrying a current $i$ produces a magnetic moment equal to $iA$ and the field due to the loop can be considered to be due to a magnetic dipole, consisting ...
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Magnetic field strength and high velocity mass levitation

I need to learn how to calculate energy requirement to levitate a mass of 5 metric tons travelling at velocities up to 27km/s. The length of the mass is projected to be 20m long and elliptical in ...
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1answer
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Is there a difference between magnetic moment and monopole moment?

I have stumbled upon the following formulation: For a magnetic pole located at $X=Y=Z=0$ with monopole moment $g=\text{constant}$, the magnetic 3-vector is given by: $\mathbf{B} = \frac{g}{r^3}(X,Y,...
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Do electron have a rotational North/South and magnetic N/S?

Out of curiosity I wonder can an electron have a rotational North/true South which is different from it's magnetic North and magnetic South, if so can we measure the precession?
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Are flywheels capable of converting torque to foward momentum?

I drew a picture of two flywheels counter-rotating in synch. While they are undergoing angular acceleration, would they propel forward? Can they be moved to reverse the torque to again propel forward? ...
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Periodic magnetic potential in quantum Hamiltonian

In the Born-Oppenheimer approximation and considering independent spinless electrons, with the following Schrödinger Hamiltonian of a crystal, $$\hat{H} = \frac{\hbar^2}{2m}\left(-i\vec{\nabla} + \...
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Taking curl of magnetic dipole potential

I am trying to find the magnetic field by taking the curl of the magnetic dipole potential. In the following, what identities must be used to go from the second to the third step? $$\nabla \times \...
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Distinguishability of classical particles with magnetic moment

Given a system of $N$ identical particles, under external field $\vec{H}$ in fixed volume $V$ and each particle has energy given by $\epsilon_{\vec{p},H}=\dfrac{\vec{p}^2}{2m} + \mu_BH\sigma$, where $\...
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Magnetic field strength from a steel rod

Suppose I have a steel bar sitting on a desk, inside the Earth's magnetic field. Suppose the bar is solid and it a cylinder, 1 meter tall and 25cm in radius. The Earth's field points uniformly through ...
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How do magnetic dipoles align with external magnetic fields?

Based on the equation for energy of a magnetic dipole in an external field: $$E=-\mu \cdot B$$ I would have thought that the system would minimise its potential energy and so the $\mu $ will be ...
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Understanding electron spin resonance

My understanding so far: Imagine a single electron all on its own. Now apply a small magnetic field along the $z$-axis. This is equivalent to making a measurement of the spin in the $z$-axis. The ...
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2answers
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Why does a magnetic field reorient another magnet along its direction?

I mean, what is the force that causes it? Is it the Lorentz force?
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Why is $m_{\ell}$ called the magnetic quantum number? What is its association with magnets?

I am going over my quantum lecture notes and I can't seem to link the quantum number $m_{\ell}$ with any magnetic property. It just seems to specify the shape of an orbital with a particular principal ...
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Probability for a group of atoms to have a certain magnetization

The paramagnetism of materials can be explained by the behavior of the alignment or not of the magnetic dipole moments of their atoms. Simply put, in a convention where the Cartesian axis $z$ points ...
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How to generalize the non-linear sigma model for general magnetic structure?

Non-linear sigma model(NLSM) is an effective model to describe magnetic behavior, which only has some phenomenology parameter $g$, $c$, and $\lambda$:$$L=\sum_i \frac{1}{g}[(\partial_\tau n_i)^2+(\...
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Magnetic dipole interaction from Dirac equation in an external EM Field

When we multiply the Dirac equation in an external EM Field: $(i\not\partial - e\not A- m)\psi = 0$ With: $(i\not\partial - e\not A + m)$ We get: $ ((i\partial_\mu - eA_\mu)^2 - e/2F_{\mu\nu}\theta^{...
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Magnetic field and magnetic field intensity and magnetisation intensity ($B$, $H$, $I$) [duplicate]

I am really confused between magnetic field (B)and magnetic field intensity(H) and magnetisation intensity(I) Please can someone explain them to me and these formula H=B/μ -I, I=M/V, I am a high ...
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Is solenoid magnetic field formula at an axial point exactly valid?

Learning about derivation of solenoid as equivalent bar magnet I came across a step raising some doubt. The first step is to take circular element of thickness $dx$ and then to calculate $B$(the ...
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Magnetisation and the field energy

"The phase with higher magnetisation has lower energy in a field; this energy difference is the driving force of the transformation." I want to fully understand this sentence (there might be a ...
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1answer
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How is the notion of minimising potential energy consistent with a magnets behaviour when placed in an external magnetic field?

If isolated systems always settle in states of minimum potential energy and $U=-\mu \cdot B$, for a magnet with magnetic moment $\mu$ in an external magnetic field $B$. It should be the case that that ...
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How to judge constitution boson “BEC” from the dispersion of bosonic quasi-particle?

We know the spin-1/2 anti-ferromagneitc (AFM) Heisenberg model can be expressed as Schwinger boson $$\begin{array}{l}{S_{i}^{+}=b_{i \uparrow}^{\dagger} b_{i \downarrow}} \\ {S_{i}^{-}=b_{i \downarrow}...
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Why is magnetization zero at optical frequencies of incident EM excitation while not at low frequencies?

In Photonic Devices by Jia-Ming-Liu, it is mentioned that magnetization at optical frequencies is zero. I know that electrons behave like an oscillator in EM fields and the amplitude of oscillation as ...
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How does shape of coil and position of magnet affect magnetic flux?

According to the equation for magnetic flux, the picture on the left (showing top view) would provide the most magnetic flux as the magnetic moment and coil area are normal to each other. But how ...
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NMR spectroscopy

I was wondering how many times larger is the magnetic moment of an electron compared to a proton? How come the electrons magnetic moment play no role in NMR and MRI? Edit Electron Spin Spectroscopy ...
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B field and H field inside a bar magnet

Recently I've been studying about magnetism there is one piece of information I'm stuck at . It says that the direction of magnetization and H field inside a bar magnet are opposite. First of all ...
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Confusion in boundary conditions of magnetic field

So the matter is I'm really confused about boundary conditions of magnetic fields. Prior to the boundary conditions, I thought that say you have an external magnetic field, $B_0$, now if I place a ...
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Reducing the switching force in a swichable magnet

I have been playing around with switchable magnets. Such as the Magswitch MS-400. I am faced with a burning question. Is it possible to reduce the force required to turn the magnet from off to on ...
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Why doesn't the vibration of atoms due to heat in a magnetic material not induce an electromagnetic field?

If an individual atom can have a magnetic field, and that atom is in motion due to heat why doesn't it induce a charge in a nearby conductor? I'd think that due to the random motion of atoms due to ...
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Anomalous magnetic moment [closed]

I have the two values of the anomalous magnetic moments: $$ a_{\mu}^{SM}=(1 165 917 760 \pm 662)\cdot 10^{-12} \\ a_{\mu}^{exp}=(1 165 920 910 \pm 630) \cdot 10^{-12} $$ Where the first is the ...
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How to calculate the mean squared radius of an atom?

I am trying to use Langevin formula for the magnetic susceptibility: $$\chi=-\mu_0\frac{e^2}{2m_e}Zn\langle r^2\rangle$$ where $Z$ is the atomic number, $n$ is the number density and $\langle r^2\...
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How according QM do permanent magnets rotate?

When two magnets are placed close to each other they turn and orient parallel. I suppose this is due mostly to spin of the unpaired electrons. But in QM a spin just orients up or down. 1. How are ...
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Why does $\zeta(3)$ appear in the expression for the anomalous magnetic moment?

The anomalous magnetic moment, to fourth order in $\alpha$, contains $\zeta(3)$. Is there a simple explanation for the appearance of this value of the Riemann zeta function?
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Magnetic Dipole Moments and Dipole Contributions

I'm currently in Physics 2 (calc-based) at my University. On the last exam we had questions over magnetic dipole moments and dipole contributions. I'm still unable to solve these problems. Would ...
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1answer
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Drone's sufficient engine RPMs initiated by Magnetic Fields

I've seen many videos where magnets are used to initiate and boost RPMs. Most of them are fake, where people are using compressed air at the backstage. Did anyone of you actually tried to challenge ...
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What is the total momentum of EM fields?

I have an assignment where i have to find the total momentum of an EM field. Imagine a perfect magnetic dipole in (0,0,0) with dipole moment $$ \mathbf{m} = m\mathbf{\hat{z}} $$ And also a point ...
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Relation between intrinsic magnetic moment and moving charges

Moving charges creates magnetic field which is relativistic effect of electric field but magnetic field is also created by the intrinsic magnetic moment. How are they related? How does intrinsic ...
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Formula for magnetic forces from neutrino magnetic moments

According to this review, the fact that neutrinos have mass imply that they also must have some magnetic moments that are around $4\times10^{-20} \mu_B$ in units of Bohr magnetons. Assuming a ...
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Magnetic dipole in a magnetic field

In this AmJPhys article Griffiths discusses stationary electric and magnetic dipoles in external electric and magnetic fields. For the case of a standard magnetic dipole (due to an electric current)...
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Symmetry reason why magnetic dipole transitions are suppressed

In the theory of light-matter interaction, electric dipole transitions between two atomic states of same parity are forbidden. This is because the Hamiltonian conserves parity. Is there a symmetry ...
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Force on a Magnetized Body in a Non-Uniform Magnetic Field

In Griffith's Electrodynamics, it is shown that when a magnetic moment, $\mathbf{m}$, is subjected to a non-uniform magnetic field, then it experiences a net force given by $\mathbf{F}=\mathbf{\nabla}...
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Interaction between electrons in which the magnetic dipole moments interact more strongly than their electric fields

Asking a question Has anyone tried to incorporate the electrons magnetic dipole moment into the atomic orbital theory?, I was curious whether anyone has attempted to relate the intrinsic property of ...
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Electron to electron interaction

I am interested to know if it would be possible to calculate the magnetic attraction between two electrons at zero space between their magnetic poles against electrostatic repulsion between them in ...
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Method for calculating nuclear magnetic moments

I am having difficulties computing the magnetic moment for an even-odd (proton-neutron) nucleus. The formula is: $$\mu_J=g_J\times j\times \mu_N$$ I checked this helpful post: When calculating ...

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