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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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How is energy conserved in this case?

Consider a permanent magnet introducing a magnetic field at some fixed angle to a loop of wire on a spindle. If a fixed current is allowed to run through the wire, the lorentz force introduces a net ...
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Torque Generated by Magnetic Field [on hold]

This is the solution that was given: I'm extremely confused how the solution is getting a magnetic field in the +y direction. I do the right hand rule and I'm getting a B into the board ...
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How to determine the best-fit magnetic dipole Gauss coefficient in a shifted coordinate system?

Introduction A planetary magnetic field $\vec{B}$ can be described outside of the planet using Gauss coefficients $g_n^m$ and $h_n^m$ and a spherical harmonic expansion: $$\vec{B} \;=\; -\vec{\...
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Is positive and negative magnetostriction attributed to the shape of the domains?

I have been reading up on magnetostriction, and noted that some materials expand while other contract in the direction of an applied magnetic field, and that it is attributed to the rotation of the ...
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Finding force from torque equation

I have read an article on electrostatics textbook that, $$\vec {F}= \nabla {\vec {\tau} }$$ Such as,the toraue equation on a magnetic dipole is $$ \vec\tau={\frac{{\mu}_0 m^2}{2\pi z^3} }\hat{z} $$ ...
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Why is the singularity not taken into account?

In this article "Reflections on Maxwell’s Treatise", Section 4.2, it says: He replaces $\mathbf{m}$ with a volume element of magnetization $\mathbf{M}\ dV$ , integrates over $V$ , and lets the same ...
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how much magnetic field is experienced at the centre of bar-magent?

What is the magnitude of magnetic field at the centre of bar magnet? What's its mathematical expression?
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Looking for an understanding of Toroidal Moments [duplicate]

The wikipedia page is not so enlightening Apparantly the Neutrino, if it is a Dirac particle, has a Toroidal Moment. Does this mean the Dirac neutrino would interact electromagnetically as well as ...
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Why does magnetic dipole moment $\vec{\mu}=\gamma \vec{L} $?

I have often seen that the relationship between magnetic dipole moment $\vec \mu$ and angular momentum $\vec{L}$ expressed as $$\vec{\mu}=\gamma \vec{L} $$ But consider a current loop of a charged ...
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Why do we think that the relation $\vec{\mu}_L=\frac{e}{2m_e}\vec{L}$ will be valid in quantum mechanics?

Assuming the electrons to revolve round the nucleus in circular orbits and using the fact from classical electromagnetism that a current loop behaves like a magnetic dipole of dipole moment $\vec{\mu}...
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Sine or cosine component of force on current carrying coil in a magnetic field

For calculating torque on a current carrying loop in a magnetic field, restoring torque that is, we use the $\tau=\vec{m} \times \vec{B}$ where $\vec{m}$ is the magnetic moment and $\vec{B}$ is the ...
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Can magnetic susceptibility χ be -1?

Is it practically possible that the magnetic susceptibility of a substance is -1? I thought so as such a substance could completely cancel the magnetic field, but I couldn't find anything as such.
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Is magnetic force relativistic effect or intrinsic property?

In this video, they explain that magnetic force is an effect of electric force due to special relativity. https://www.youtube.com/watch?v=1TKSfAkWWN0 But then, the same authors explain in this video ...
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Force on a magnetic dipole in an external magnetic field

I want to find an expression for the force acting upon a magnetic dipole with dipole moment $\mathbf{m}$ if that dipole is positioned in a stationary, external magnetic field $\mathbf{B}$. The ...
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Magnetic material demagnetization through Curie temperature

It is known that some materials lose their permanent magnetic properties when they are heated above certain temperature known as Curie temperature or Curie point. As those materials are cooled down to ...
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Parameters Affecting Demagnetisation

What parameters will affect how a ferromagnetic material is demagnetised? Assuming that only changing fields will induce demagnetisation (although I suppose I could well be wrong on that one), what ...
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Magnetic field around solenoid and toroid

Solenoid is proving a little bit confusing While getting through solenoid I found that the field outside it is extremely small and is negligible. Also the field at ends is half of that of center. ...
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Magnetic moment of a radially symmetric current

In my latest assignment I'm tasked with finding a magnetic moment $\mu$ of a hydrogen atom, whose current distribution $\mathbf{j}(\mathbf{r})$ looks like $$\mathbf{j}(\mathbf{r})=\frac{e\hbar}{3^8 \...
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Explanation for magnetic declination [closed]

A compass in New York points about 15 degrees west of true north; in California, it points about 15 degrees east of true north. Magnetic declination also varies with time. What are some possible ...
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Two questions about electron's magnetic spin

Does electron's magnetic spin mean that we can think of it as having the two magnetic poles? Does the spin mean that it generates magnetic field even if it is at rest? I expect to get 'no' to both ...
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How does the atomic magnetic moment get locked with external magnetic field?

When an atom has a net magnetic moment that is not aligned with external magnetic field, it is said that the atom rotates because of the torque and the magnetic moment gets aligned with external field....
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How much time does it take magnetization to appear, after turning on a magnetic field?

When a magnetic field ${\bf H}$ is turned on from zero, a piece of material, not previously magnetized, exhibits a magnetization ${\bf M}$ due to ${\bf H}$. According to ${\bf M} = \chi {\bf H}$, ...
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How do magnets move towards or away from each other?(Explanation on a molecular level)

Imagine two magnets on a horizontal surface, with two opposite poles facing each other. If one of them is north, then the other magnet with the south pole facing the north will move towards the north ...
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Are permanent magnets a relativistic effect?

The relationship between Electromagnetism and Special Relativity is something that always amazed me but I haven't fully understood yet. Misconceptions and contradictions seem to be widespreaded, and ...
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Why do the spins follow the bar of the magnet when you turn it in your hand? [closed]

So we know from experience that when we turn a magnet in our hand, the magnetic dipole doesn't lag behind. So if the magnet (and its dipole) is pointing down, when we push on the material of the ...
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Magnetic Shielding

Imagine a substance in an electric field. You don't want the electric field to interact with the object you have put in its way. What should be the type of material this magnet should be made of to ...
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Which factors determine which pole is going to be N and S in the broken pieces of the magnet?

Let's suppose that there is a magnet with a north and south pole and we break this magnet randomly. Which factors determine which pole is going to be N and S in the broken pieces of the magnet.
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Stationary electromagnet(s) to move a metal rod.

I would like to use an electromagnet(s) to move the metal rod depicted bellow in the side view, it moves in the direction of the arrow the rod requires 5.39N of manual force to travel in the depicted ...
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Hamiltonian for a magnetic field

An atom has an electromagnetic moment, $\mu = -g\mu_B S$ where S is the electronic spin operator ($S=S_x,S_y.S_z$) and $S_i$ are the Pauli matrices, given below. The atom has a spin $\frac{1}{2}$ ...
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Classically, if the magnetic moment of a particle is aligned with a time-varying magnetic field, can its spin flip?

Consider the time-varying magnetic field: $$ \mathbf{B}=B \tanh{\Big(\frac{t}{\tau}\Big)}\hat{\mathbf{z}}. $$ If the magnetic moment (which is proportional to the angular momentum) of a particle at $...
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Can the spin of a spin-$1/2$ particle flip in a time-varying magnetic field?

Given that the state of the particle at time $t=-\infty$ is $\left|S_z^+\right>$, a magnetic field of the form $\mathbf{B}=B \tanh(t/\tau) \hat{\mathbf{z}}$, the Hamiltonian is $H=-\vec{\mu}\cdot\...
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How are these “supplementary” or “satellite” Helmholtz coils used?

Three mutually orthogonal pairs of Helmholtz coils can be used to produce a fairly uniform magnetic field of arbitrary direction within a certain volume, and/or to null/cancel an external field (e.g. ...
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When does $\nabla \times B =0$?

In my lab, I use electromagnets to apply a magnetic gradient force to lots of very small (superparamagnetic) nanoparticles embedded in an elastic medium. I believe that these can be treated as ...
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Why magnetic dipole moment are important

After reading the Chapter 35 of Halliday Resnick and Krane's Physics, which is the section on magnetism in which magnetic dipoles are introduced, I still don't understand why the particular quantity ...
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Permanent magnets - Attraction with no repulsion

I have some permanent "refrigerator" magnets and noticed that, though they attract the refrigerator, they also attract each other (there is only one side available for the magnet, the other side has a ...
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Reversing magnet polarity to increase/decrease Eddy currents?

I have a cast iron wheel with magnets around the inner radius as a braking mechanism. If I were to add additional magnets around the outer radius, would the amount of Eddy currents increase or crease ...
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Magnetic Dipole from 'Current' in LC Circuit

We can work out the 'current' in an LC (series) circuit by creating and solving an ODE: $$I\frac{1}{LC}+\ddot{I}=0$$ This provides us with a sinusoidal resonant response to any initial current. ...
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Increasing Eddy current induced within surface by attaching a magnet on surface

Magnets are commonly used in magnetic exercise bikes as brakes for increasing resistance: where the black wheel is a piece of cast iron. I was wondering if (significantly) more eddy currents would be ...
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Joining poles of bar magnet

What happens when 2 poles(i.e. noth and south) of the same bar magnet joined to each other to form circular loop?
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Why are there sine and cosine in the magnetic dipole moment (in the torque formula) of a rotating conductor loop?

I'm trying to redo the textbook example in magnetostatics. The current carrying loop is affected by a magnetic flux in the ax→ direction. While trying to find the torque on sides ab and cd for figure ...
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Does the magnetic field line passing along the axis of a bar magnet ever reaches to South Pole?

Consider a bar magnet, and the magnetic field line that goes through its axis and through the center of its north pole and thus follows a straight line path out of the magnet. Will this line ever be ...
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Simplification of an expression with gamma matrices [closed]

I am trying to understand the details of the calculations involved in determining the electron's anomalous magnetic moment to second order: the $\alpha/{2\pi}$ term. There is just one step, where an ...
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Special relativity constrains massless electric dipoles, but not massless magnetic dipoles?

Discussion in comments on the two questions linked below leaves me confused about the following point. We expect a magnetic or electric dipole to make a field that has some universal transformation ...
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Why is a current carrying loop considered a dipole?

I am unable to understand why a current carrying loop is considered a dipole. Why exactly is it called a "dipole", which two poles are we referring to and how do those two poles function as the north ...
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Relaxation spectrum and time dependence of magnetic moments

Consider a thermally isolated ferromagnetic crystal above but near its Curie temperature in a bias field such that the magnetization is essentially saturated. Now remove the bias field as fast as ...
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If I use a magnet to levitate another magnet, where is the energy coming from?

Imagine I use one static magnet to levitate another magnet indefinitely. This levitating magnet is in a narrow tube that wont allow it to rotate and get attracted. So it will keep levitating forever, ...
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What happens while breaking a Bar magnet?

If we have a bar magnet and we break it as shown below Then as per the image we get two bar magnets But does this happen instantaneously or there is some time lag between this process. Or simply, Can ...
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Why is Ampère's law violated if there are no fringe fields?

What's wrong in this diagram? The reason is this: magnetic field lines between the two poles of magnet are perfectly straight in the given diagram, which is not possible. Fringing effect of the ...
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Magnetic moment of hydrogen atom in weak magnetic field from hyper fine structure

So I need some help with this question, which is formulated: "Calculated the total magnetic moment of a hydrogen atom in the ground state in a weak magnetic field which arises from hyper fine ...
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How to mathematically represent Néel state

Néel state is (approximate) ground state of anti-ferromagnet in which nearest-neighbor spins are align in opposite direction i.e. $$\uparrow\downarrow\uparrow\downarrow\uparrow\downarrow\uparrow\...