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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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Please explain the solution to this magnetic moment question [on hold]

I cant understand this question please explain it to me
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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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52 views

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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26 views

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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1answer
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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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54 views

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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Does a moving charged particle experience a force due to the magnetic dipole moment it produces interacting with external magnetic fields? [duplicate]

I have feeling that the force on a moving charged particle from an external field is due to the interaction of the external magnetic field with the magnetic field produced by the charged particle. ...
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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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1answer
36 views

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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1answer
32 views

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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1answer
30 views

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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2answers
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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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128 views

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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How does one measure the Lande $g$-factor of electrons in water?

In our lab, we have measured the Lande $g$-factor of the lone loosely bound electron in DPPH. Can we do the same experiment (Electron Spin Resonance) with water as a sample?
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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\...
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What happens when a bar magnet is cut in half?

What happens when a bar magnet is cut perpendicular to its axis of magnetization? On searching the internet, there a lot of people who suggest pole reversal occurs and the cut ends repel each other, ...
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Can the $s=1, m_s=0$ member of the spin triplet state lead to ferromagnetic alignment?

Ferromagnetism corresponds to the parallel alignment of spins, and it is said that for ferromagnetic alignment one requires the spin part of the wavefunction must be in one of the three symmetric ...
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Why does magnetic moment of a material oscillate with the inverse of magnetic field?

I'm studying magneto oscillatory behaviour, and up to the point of a B field creating circular levels in k-space, I am fine at this level. Can someone explain to me physically with as little maths as ...
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Expectation value of the magnetic moment

I am reading H. Ibach's Solid state physics on chapter 8. I am confused about the equation 8.10 that states the expectation value of a magnetic moment in a state $\psi$ is: $$ \boldsymbol{m}=\frac{\...
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How long does it take for a magnet to rotate to being parallel with magnetic field from Helmholtz coil?

In a physics project, we're making a Helmholtz coil, and placing a magnet orthogonal to the magnetic field from the coil. When the coils are turned on, the magnet will rotate to align with the coils ...
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1answer
113 views

How do electrons actually move in the Stern Gerlach experiment?

As I understand it, the Stern-Gerlach experiment discovered: Fire an electron horizontally through a vertical magnetic field. Then, beyond the acceleration $e \textbf{v}\times \textbf{B}$ due to its ...
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Magnetic moment force

I have two magnets with magnetic moment in the order of 10 emu pointing in the same direction and both in the $z$-axis a distance of 20 nm. What is the force that repels both magnets? I know the ...
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1answer
99 views

Magnet going through a current carrying loop

Consider a small magnet that is suspended just above a conducting fixed loop placed. The magnet is oriented perpendicular to the axis of the loop and is released to fall under gravity and at the same ...
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2answers
135 views

How can neutrinos have a magnetic moment in spite of being neutral and elementary?

How can neutrinos have a magnetic moment in spite of being elementary (as opposed to a neutron) and electrically neutral (as opposed to a proton)? How can it even be defined, and measured?
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Why Earth is like a magnetic dipole?

Earth’s magnetic field is mostly caused by electric currents in the liquid outer core, which is composed of conductive, molten iron. Loops of currents in the constantly moving, liquid iron create ...
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Intuition on Magnetic Dipoles and Magnetic Moment

1) Magnetic Moment in terms of magnetic poles: According to Wikipedia, " Magnetic poles always come in pairs, their forces partially cancel each other because while one pole pulls, the other repels. ...
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Derivation of Bohr magneton; how is the angular momentum derived if not from spin?

I'm trying to understand the derivation of the Bohr magneton $m_B$. The Bohr magneton is a calculation of the magnetic moment of a charged particle with some angular momentum. Generally, magnetic ...
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Force caused by the magnetic field on the electron spin

I have read there are two ways to express the force caused by a variable magnetic field over a magnetic moment depending on the source of the magnetic moment since it can come from a dipole or a loop ...