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.
Questions tagged [magnetic-moment]
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Resolving Conflicting Reports on Fermilab $g-2$ Results
Today it was announced that the Fermilab measurements of the muon's gyromagnetic ratio are in disagreement with the Standard Model with a statistical certainty reported at 4.2 sigma [1, 2], raising the distinct possibility that the discrepancy…
Kai
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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 feasible to redirect nearby fields and curve the field…
mugetsu
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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 symmetry axis with angular velocity $\omega$. What…
Andrew
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Why compass needle doesn't precess about but aligns by magnetic field?
A magnetic dipole in magnetic field, precess about the axis of magnetic field. So why compass needle doesn't precess but lines up with magnetic field?
moshtaba
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Why Is an Inhomogenous Magnetic Field Used in the Stern Gerlach Experiment?
The apparatus used in the Stern Gerlach experiment is somewhat like the one shown below with magnetic pole pieces of different shapes producing an inhomogeneous magnetic field.
But what would have happened if we had used symmetrical pole peices…
Martin Medro
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Paradox about the Stern-Gerlach experiment with $B=0$, $\nabla B\ne 0$
In a modern interpretation of the historical Stern-Gerlach experiment, a beam of neutral silver atoms, each with spin 1/2, was sent in the z direction through a nonuniform magnetic field having both a nonzero value and a nonzero derivative, i.e.,…
user4552
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Relation between magnetic moment and angular momentum -- classic theory
How do I prove the relation between the vectors of magnetic moment $\vec\mu$ and angular momentum $\vec L$, $$\vec\mu=\gamma\vec L$$ ?
Many text books and lecture notes about the principles of magnetism show the relation of $\mu$ and $L$ as scalars…
killozap
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How does a spinning electron produce a magnetic field?
I learned in my undergraduate physics class that atoms have magnetic fields produced by the orbit of electrons and the spin of electrons. I understand how an orbit can induce a magnetic field because a charge moving in a circle is the same as a loop…
Tad
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Could someone explain the muon $g-2$ experiment problem?
In the past days it was announced that the lastest results of the muon $g-2$ experiment indicates some discrepancies with the standard model. As an outsider in particle physics, I don't understand exactly what's happening and my only sources have…
JustWannaKnow
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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.
$$\frac{\partial M_x}{\partial t}=({\bf M} \times \gamma {\bf H_0})_x-\frac{M_x}{T_2} $$
$$ \frac{\partial M_y}{\partial t}=({\bf M} \times…
Rich
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How to calculate the magnetic dipole moment of a bar magnet?
I want to calculate the force between two magnets. In a previous Phys.SE question, I was told that I needed to use the dipole-dipole interaction, but that equation depends on $m$, the magnetic dipole moment of the magnet.
How do I calculate $m$? I…
user28324
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How does magnetic moment vector arise from spin 1/2 spinors?
In NMR a hydrogen proton magnetic moment is a vector due to spin, but spin 1/2 like protons are spinors, not vectors, so how does spin 1/2 spinor give rise to an actual magnetic moment?
Johnson
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How accurate is the magnetic field determined by assuming a circular current carrying loop as a magnetic dipole?
I've learnt that a circular loop of area $A$ carrying a current $i$ produces a magnetic moment equal to $iA$ and the field due to the loop can be considered to be due to a magnetic dipole, consisting of two magnetic charges (magnetic monopoles) -…
Vishnu
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Non-Relativistic Electron Hamiltonian
I have determined a Hamiltonian for an electron using an appropriate Lagrangian of the form
$$…
Sam
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What will happen to a permanent magnet if we keep the same magnetic poles of two magnets close together for a long time?
What will happen to permanent magnet's magnetic field or magnetic ability if we keep same magnetic poles of two permanent magnet for long time?
Will any magnetic loss happen over the long period of exposure or does the magnetic strength remain the…
Ganapathy C
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