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10
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1answer
283 views

Nuclear Magnetic Resonance (NMR) Conceptual Questions

Let $M$ be the magnetic moment of a system. Below are the Bloch equations, including the relaxation terms. $$\frac{\partial M_x}{\partial t}=({\bf M} \times \gamma {\bf H_0})_x-\frac{M_x}{T_2} $$ ...
6
votes
2answers
137 views

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 ...
4
votes
1answer
753 views

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), ...
4
votes
0answers
68 views

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?
3
votes
3answers
2k views

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?
3
votes
2answers
196 views

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 ...
3
votes
2answers
163 views

What is the physical significance of the Dipole Transformation of Maxwell's Equations?

The Question Given Maxwell's equations of the form \begin{align} \bar{\nabla}\times \bar{B} = \dfrac{4\pi}{c} \bar{J} + \partial_0 \bar{E} \\ \bar{\nabla}\times \bar{E} = -\partial_0 \bar{B} \\ ...
3
votes
2answers
477 views

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 ...
3
votes
1answer
137 views

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 ...
3
votes
1answer
206 views

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 ...
3
votes
3answers
90 views

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?
3
votes
0answers
203 views

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 ...
2
votes
1answer
455 views

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 ...
2
votes
4answers
241 views

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 ...
2
votes
3answers
111 views

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 ...
2
votes
1answer
386 views

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 ...
2
votes
2answers
279 views

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 ...
2
votes
1answer
28 views

Torque on wire summarized with magnetic moment

The magnetic moment of a current-carrying wire loop $L$ is $$ \boldsymbol\mu = \frac I2\oint_L\mathbf{r} \times \mathrm{d}\mathbf{r} $$ so the torque it experiences under a uniform magnetic field ...
2
votes
2answers
49 views

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 ...
2
votes
1answer
121 views

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 ...
2
votes
3answers
176 views

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 ...
2
votes
1answer
104 views

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}' ...
2
votes
0answers
769 views

How to calculate magnetic pole strength?

I have 2 magnets. I need to know the force between them. In a previous Phys.SE question, conclusion was: we need to use a dipole-dipole interaction equation, which included m, which the magnetic ...
2
votes
0answers
51 views

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 ...
1
vote
3answers
133 views

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 ...
1
vote
2answers
208 views

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 ...
1
vote
3answers
471 views

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 ...
1
vote
2answers
117 views

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 ...
1
vote
2answers
199 views

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 ...
1
vote
1answer
183 views

$E\times B$ 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 $v_E$ ...
1
vote
3answers
598 views

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 ...
1
vote
1answer
140 views

Force from solenoid

I'd like to approximate the force from a solenoid, or at the very least find a formula which is proportional to the force so that I can experimentally find the constant for my particular case. ...
1
vote
0answers
99 views

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 ...
1
vote
0answers
117 views

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 ...
0
votes
2answers
180 views

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 ...
0
votes
1answer
85 views

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 ...
0
votes
3answers
384 views

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 ...
0
votes
0answers
16 views

How is demagnetizing field described when using Ampére's loop current?

A magnetic moment is sometimes described using circular current loop instead of dipoles. In that case, how do you define the demagnetizing field? Say you have a circular current loop centered on ...
0
votes
0answers
30 views

Opposite field's acting on a soft ferromagnetic material

To external fields(H, - H) not equal to each other are acting on that material. Based on the hysteresis loop what would be the result? The hysteresis area of that materials is very narrow(i.e easy to ...
0
votes
0answers
53 views

Magnetization energy density and Magnetic field energy density.

Are they the same? I mean the energy required to magnetize/demagnetize a ferromagnet is highly dependent on the hysteresis loop that is $E= \int H dB$. The energy density of the same field is equal ...
0
votes
0answers
39 views

Spin angular momentum AND spin magnetic moment [duplicate]

Since magnetic moment come from circulation of current or magnet. Because spin of electron is not classical spin of body so what is origination of spin magnetic moment and angular momentum? Is ...
-1
votes
1answer
61 views

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 ...