What is Magnetic moment: Definition and 181 Discussions
The magnetic moment is the magnetic strength and orientation of a magnet or other object that produces a magnetic field. Examples of objects that have magnetic moments include: loops of electric current (such as electromagnets), permanent magnets, elementary particles (such as electrons), various molecules, and many astronomical objects (such as many planets, some moons, stars, etc).
More precisely, the term magnetic moment normally refers to a system's magnetic dipole moment, the component of the magnetic moment that can be represented by an equivalent magnetic dipole: a magnetic north and south pole separated by a very small distance. The magnetic dipole component is sufficient for small enough magnets or for large enough distances. Higher-order terms (such as the magnetic quadrupole moment) may be needed in addition to the dipole moment for extended objects.
The magnetic dipole moment of an object is readily defined in terms of the torque that object experiences in a given magnetic field. The same applied magnetic field creates larger torques on objects with larger magnetic moments. The strength (and direction) of this torque depends not only on the magnitude of the magnetic moment but also on its orientation relative to the direction of the magnetic field. The magnetic moment may be considered, therefore, to be a vector. The direction of the magnetic moment points from the south to north pole of the magnet (inside the magnet).
The magnetic field of a magnetic dipole is proportional to its magnetic dipole moment. The dipole component of an object's magnetic field is symmetric about the direction of its magnetic dipole moment, and decreases as the inverse cube of the distance from the object.
Ich wäre Ihnen sehr dankbar, wenn Sie sich meine Lösung der folgenden Übung ansehen:
A sphere with radius ##R ## is spatially homogeneously loaded and rotates with constant angular velocity ##\vec{ \omega}## around the ##z ## axis running through the center of the sphere.
Calculate the...
from the partition function - am trying to show that ##\langle \mu \rangle = \beta^{-1} (\partial \log Z / \partial B)## where ##Z## is the canonical partition function for one atom, i.e. ##Z = \sum_{m=-j}^{j} \mathrm{exp}(\mu_0 \beta B m)##, and ##\mu = \mu_0 m##. The average...
Can you cite experiments where, in some excited states of a hydrogen atom, magnetic moment significantly differs from Bohr's magneton was detected? Correction for magnetic moment of nucleus is insignificant. Only experimental data, not theoretical forecasts. Starting from the experiments of...
We know that we need to go to 5th order in perturbation theory to match 10 decimals of g-2 for electron, theory vs. experiment. But let us not assume QED is pure and independent, but it's a lower energy limit of GSW (not Green-Schwartz-Witten from superstrings) electroweak theory. Has anyone...
* The general formula for the magnetic moment of a charge configuration is defined as ##\vec{\mu} = \frac{1}{2} \int \vec{r} \times \vec{J} \,d^3r##* For an electron it's said that the correct equation relating it's spin and magnetic moment is is
##\vec{\mu} =g\frac{q}{2m}\vec{S}##
* It's...
How would you go about calculating the work done in morphing a square current-carrying loop into a circular current-carrying loop, without change in length while maintaining the same angular orientation with an external magnetic field.
My book suggests defining P(potential energy) = M.B (dot...
i recently read about the stern-gerlach experiment and found out that they did it in the first place to verify the principle of the "space quantization " introduced by Bohr , and they thought they did detect the quantization of the orbital angular momentum of ( L = 1 , m = 1,-1 ) neglecting the...
Hello! I want to make sure I understand (mainly qualitatively) what happens to an atom in a magnetic field. Assume we have an atom with an even number of protons and electrons. This means that all proton (electrons) are paired up, except for one of them (I am not totally sure if this pairing is...
Is Peskin and Schroeder book, page 187 when they try to connect the electron form factors to its magnetic moment they get the expression
$$\bar{u}(p')\left(\gamma^i F_1(q^2)+\frac{i \sigma^{i\nu}q_\nu}{2m}F_2(q^2)\right)u(p)$$
Where ##p##, ##p'## are the momenta on on-shell electrons and...
About this figure, the current in the opposite wires are parallel (and not anti-parallel). So, for instance for the first option the torque is zero; but I wanted to know what is the magnetic moment of this loop. Since I rely only on formula I've have no idea how to compute for this one.
So far the best I've been able to come up with is to use ##\vec{B} = \mu_0 \vec{H}## which gives me
i_c = H 2\pi r
j_c = \frac{H 2\pi r}{\pi r^2} = \frac{2H}{r}
\therefore B = \mu_0 \frac{r j_c}{2}
I'm fairly confident this is just terrible math and physics on my behalf but I'm struggling to...
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...
Hello there!
I'm trying to check the first order (1 loop) correction to the electron magnetic moment. I'm following Schwartz and Peskin, but both of them have a point where they hide the calculations, and I'm not sure if my calculations are correct.
The point is exactly this:
I don't know...
I am trying to derive the equation ##\vec{\Gamma} = \vec{m} \times \vec{B}##, where ##\vec{m} = I \vec{A}## is the magnetic moment, and ##\vec{A}## is normal to surface ##A##, from the Lorentz force law ##\mathrm{d}\vec{F} = I \vec{dl} \times \vec{B}##. For an arbitrary closed current loop ##C##...
Hello! I am reading Schwarz's book on QFT and in chapter 17 he introduces the anomalous magnetic moment. I am not sure I understand a step in the derivation (from a mathematical point of view), when going from 17.23 to 17.24 (I attached a SS of it). I was able to get certain terms, but I am not...
I know that total magnetic moment of an electron (I am not sure if it is magnetic moment of electron or atom, please clarify this) is sum of magnetic moment caused by orbital motion and spin angular momentum.
So,
Total magnetic moment = Orbital magnetic moment + spin magnetic moment
Do I have...
I tried to calculted the rotating speed fro a proton from the clasical point of view by using its magnetic moment and the moment of a rotating sphere uniformly charged as example here: https://ocw.mit.edu/courses/physics/8-07-electromagnetism-ii-fall-2012/exams/MIT8_07F12_quizsol2.pdf
It is said...
Could I have hundred times the ground state or there is a limit?
Is there a limit for excited magnetic momentum that if reached the nucleous explode or generate gammas?
I suppose If I excite it it would spin faster but proportional to quantum values. Note: there is a "theory" to avoid electron...
Homework Statement
a magnetic moment of U = 1 (i) + 2 (k) , surrounded by a magnetic uniform field of B= 3 (i) + 4 (j) - 1 (k)
find the potential energy in mJ ?
Homework Equations
dot product of 2 vectors
( ui*bi)+(uj*bj)+(uk*bk) =
or finding the module of both vector and doing AB...
"Calculated the total magnetic moment of a hydrogen atom in the ground state in a weak magnetic field which arises from hyper fine splitting of the ground state. How many beams does hydrogen produce from a Stern-Gerlach analyzer with a weak magnetic field?"
I've calculated the magnetic moments...
For an undergraduate project, I need a magnet with a magnetic dipole strength of 0.3 A*m^2. However, all distributors I can find only list their magnets in terms of "pull force" which appears to be defined as the force between a magnet and a steel plate. How do I find a magnet with the dipole I...
The spin magnetic moment of a charged, spin-1/2 particle is
$$g \frac e {2m} \frac \hbar 2$$
where g is the g-factor (2 for any particle in tree-level approximation, 2.00231930436182 for electron),
e is charge
m is mass
##\frac \hbar 2## is spin
But with zero mass this expression does not make...
Homework Statement
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Consider the hydrogen atom in the 42F5/2 state. Take into account the effects of finestructure (spin-orbit coupling).
(a) Write down the spectroscopic notation of the state that the 42F5/2 is degenerate with, in the absence of an external magnetic field.
(b) Calculate...
Homework Statement
Find the magnetic moment of a crystal when placed
(i) in a weak field at high temperature
(ii) in a strong field at low temperature
Homework Equations
This is the last part of a question which I feel I have solved correctly up until this point.
The mean magnetic moment I...
I was reading the statistical physics textbook and was really confused with the notation:
I don't understand the last part of the section. Why is that \sum_{\sigma = \pm1} \sigma P(\sigma) equals to \left< \sigma \right>? And what does \left< \sigma \right> actually mean? Is it the average...
If electrons have a magnetic moment (or behave like they have) why don't all orient North Up in a magnetic field (pointing down)? Plus, if thought as magnetic dipoles, like poles repel, therefore all should point the same direction. In a Stern-Gerlach apparattus shouldn't the magnetic moment...
In exam we have a question like this ,
I said its false cause ##U=-\vec μ⋅\vec B## , ##U=-μBcosθ## when ##cosθ=1## it is in the most stable point.But when ##cosθ=-1## its not, since.In both cases ##\vec μ## and ##\vec B## are parallel ?
Homework Statement
A 15-turn rectangular loop of wire of width 10 cm and length 20 cm has a current of 2.5 A flowing through it. Two sides of the loop are oriented parallel to a uniform magnetic field of strength 0.037 T, and the other two sides are perpendicular to the magnetic field. (a) What...
Every magnetic object has a magnetic moment. From electrons to molecules, to even planets.
But my question is, what determines how much of a magnetic moment a quantum object has? I'm not sure if "how much" is the right word for it. What determines the "quantity" of a magnetic moment of a...
https://link.springer.com/chapter/10.1007/978-3-540-39664-2_1
http://iopscience.iop.org/article/10.1088/0031-8949/1988/T22/016/pdf
In these two experiments done back in the 80's, electrons were trapped inside a penning trap for long periods of time. They were measuring the ratio of the magnetic...
I'm told that the MnO crystal resembles in structure that of NaCl (FCC) with lattice constant a, and am first asked to write a general expression for the position vector Rj of the ion j in the unit cell of MnO. I am then asked to find the vector K for MnO in order to use the relation...
Homework Statement
In classical physics, a system's magnetic moment can be written like so: \mu = g\frac{Q}{2M}L, where ##Q## is the total charge, ##M## is the total mass of the system and ##L## the angular momentum.
a) Show, that for a cylinder (##I = \frac{1}{2}MR^2##) spinning around its...
When I induce magnetic flux through a closed loop, I should expect the lines of flux produced by current in that loop to oppose the change of flux through that loop. But what happens when that loop, say a rectangular loop, is curved into the shape of the letter J (like a candy cane) and my flux...
I read that the stoichiometric half-metallic compound has integer spin moment. For this, n(up)-n(down) should be integer. Since n(up) +n(down) is always integer, either n(up) or n(down) should be integer to make total spin moment integer. I could not understand how the presence of energy gap in...
Hey there!
I would really appreciate if someone could help me with the following problem. I didn't find it anywhere (textbooks, web...).
Not only currents but also magnetized bodies possesses magnetic moment. I know that if the magnetized body is at rest in a constant external magnetic field...
How is it calculated from magnetic susceptibility measurements using the mass of the sample?
I know only this formula https://en.wikipedia.org/wiki/Magnetic_moment#Magnetic_moment_of_an_atom, but there is no mass, only quantum numbers.
I'm asking the above question as I imagined a current loop made out of a curving wire that cannot fit into a flat plane.
Where does the direction of μ point then?
Also, is there only one μ value for any current loop, independent of the chosen axis of tilting?
Or can a current loop have...
Hey all, I'm having some issues with electromagnetism here.
Let's say we have a particle with magnetic moment ##\vec{\mu} = \mu_0 \hat{x}## and magnetic field ##\vec{B(x)} = B_0 \frac{x}{a} \hat{x}## where ##\mu_0,B_0,a## are constants.
If we assume that the magnetic field ##B_0## is far, far...
The magnetic moment ##\vec{M}## of a charged particle is defined as ##\vec{M}=\frac{1}{2}q\,(\,\vec{r}\times\vec{v})##.
Starting with torque ##\vec{N}=\vec{M}\times\vec{B}##, I arrive at a contradiction.
Consider a charge particle moving at a constant speed ##v## anticlockwise in a circle of...
Every magnetic dipole has a magnetic moment associated to it. Magnetic moment of electromagnets could be found by ##M = iA##. But for permanant magnets how it is measured? If we use this formula it implies that there must be some internal current flowing in permanant magnet.
Is it true?
What...
Homework Statement
If there's a current I flowing through the rectangular conductor and it's located in the magnetic field in such way that normal vector of the surface that this rectangle forms closes the angle of 60 degrees with magnetic induction vector find total magnetic moment of this...
Dear All,
Hi, I am pretty new in the area of magnetism. Please pardon me for some questions that might be pretty fundamental and basic here.
I am trying to understand the difference between magnetic moment and magnetization. I thought I understood magnetization as the degree to which a magnet...
Homework Statement
Describe, with examples, what is meant by magnetic moment. What gives rise to a magnetic moment in a proton/neutron?
Homework Equations
The Attempt at a Solution
I know what a magnetic moment is, just struggling with the other parts of the question.
So what I'm thinking is...
Homework Statement
A circle-formed circuit with an area A lies in the (xy)-plane. An electric current I runs clockwise through the circuit (figure 1). An external magnetic field B exerts a torque t = D(3i - 4j) on the circuit, where D is a positive constant, i is the x-axis unit vector and j is...
Homework Statement
A bar magnet floats above another bar magnet. The first has mass u1 and magnetic moment m1=m1k^ and is on the ground. The second has mass u2 and mag. moment m2=-m2k^ and is a distance z above the ground, find z
2. Homework Equations
I assume I need to calculate the magnetic...
Homework Statement
I'm working on a problem that says that
>If $\varepsilon_{\pm}=\mp (\mu \mu_0 H + k \theta \frac{M}{\mu N} )$ is the energy of the atom of a specimen that can orient itself either parallel or antiparallel in a magnetic field, show that $ \frac{M}{\mu N}= tanh(\frac{1}{kT}(...
Homework Statement
Find spin only magnetic moment of ##[Fe(H2O)5NO]^{2+}##
Homework Equations
None
The Attempt at a Solution
When I used Google, the magnetic moment in 3.87
##Fe## is in +1 oxidation state. So configuration is $$[Ar]3d^64s^1$$
There are 5 unpaired electrons. How does magnetic...