Questions tagged [magnetic-fields]

For questions that utilize the concept of magnetic fields (commonly denoted by the letter B), or for questions whose answers likely involve magnetic fields. More specific than the [magnetism] tag, as questions about the phenomenon & theory of magnetism do not necessarily involve the discussion of fields.

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Larmor precession and atomic magnetic dipole moment

I'm hoping someone can help me understand why a classical atomic magnetic dipole moment precesses around the direction of an applied magnetic field, rather than simply aligning with the field. From ...
dgwp's user avatar
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How can I estimate the force of an electromagnet?

I am doing an experiment on electromagnetism, basically I am just testing the pulling force of an electromagnet using a newton meter with a magnetic hook and seeing how the pulling force changes as i ...
Matias Red's user avatar
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Using the magnetic masses model how do i find the induced magnetic field due to a magnetic point charge?

I am deriving an equation modelling a magnetic guitar pickup and I am stuck. I am trying to derive based on a paper for guitar pickups and it uses a magnetic masses method to find the magnetic flux at ...
KL Web Design's user avatar
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Superconductor Cube levitating in Vertical magnetic field

Suppose there's a Magnetic field in vertical direction and we hold and release a superconductor cube so experimentally it is seen that the cube floats/hovers in the same orientation as it was released ...
Macron's user avatar
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How does plate thickness affect magnetic levitation?

I’ve been watching videos: Like this about magnetic levitation. They have a copper plate, normally quite thick, a smaller disk magnet under, and a larger disk magnet on top. Upon movement of the ...
SpiralingTessaract8164's user avatar
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How do the currents induced by the $E$-field and $H$-field flow? Which of the two currents induced by $E$ or $H$ has the larger amplitude?

I came across this problem for an exam preparation question, which I am struggling to answer. Consider a sphere made of thin metal, with a radius of 1 m, at 20 km distance from an AM transmitter ...
HAPU's user avatar
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5 votes
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Time for ferromagnet to align with magnetic field

A ferromagnet is inside a solenoid. When the current in the solenoid flips its direction, the solenoid magnetic field flips. As a consequence, the ferromagnet magnetization flips. What determines the ...
Rd Basha's user avatar
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Can a homogenous electric/magnetic field vary in time?

In either case I was thinking their curl is cero since they're homogenous. But that only leaves with $- \frac{\partial B}{\partial t}=0$ for example, but then?
MarioPEM's user avatar
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Isn't linearly polarised light actually chiral or am I stupid?

Isn't linearly polarised light actually chiral when taking the magnetic field into account? Just looking at the electric field is just 2D and therefore achiral, obviously. But with the magnetic field ...
Jorge's user avatar
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Why the Sun does not shoot relativistic jets?

I saw the features of the Sun here and it has almost everything include nanojets and CME but not relativistic jets. Isn't the Sun magnetically active so why isn't it capable of shooting out ...
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Force on Neodymium Magnet due to Magnetic Field from Electromagnet

I am a mechanical engineer currently in a university research program, and my project involves mixing bonded neodymium powder (Magnequench for those who are interested) into a polymer in order to ...
Thomas's user avatar
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Magnets in 2 Spatial Dimensions?

In 2+1 dimensions of spacetime, the electromagnetic field is made up of a vector electric field and a scalar magnetic field. At each point in space, there is a magnetic field value, which we can ...
Anthony Khodanian's user avatar
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How different is the induced magnetic field of a coil with a solid rod core and a sheet-wrapped one? (Assuming both use the same material)

I'm doing research for a university project and looking for commercial references for Mu metal, I found out that in my country at P2B (particular to business) level, sheets are significantly easier to ...
murisio's user avatar
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Does the Change in Area Not Affect EMF Calculation in a Time-Varying Magnetic Field?

I had this Question as a Homework : Given a conducting frame of width $𝐿$. A mobile conductor is mounted on the knitting needle that moves on the closing one at speed $\vec{𝒗} = 𝑣\hat{x}$ while ...
Losh_EE's user avatar
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Line Width of Resonance Peak in NMR Experiment

I'm studying the NMR experiment at the moment and was wondering what the line width of the resonance peaks represents? When I've looked into it, it just comes up with the definition that it's 'the ...
user374355's user avatar
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Magnetic Levitation Question

For a physics project, I am experimenting with magnetic levitation. The goal of the project is to levitate a magnet on top of a plate of material. The guidelines for the project are that the plate ...
SpiralingTessaract8164's user avatar
2 votes
1 answer
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Does parasitic capacitance contribute to the magnetic flux?

When modeling a real inductor, typically the equivalent circuit is the following one: Source A series resistance and parallel capacitor is added. This model works very well to explain the following ...
rr1303's user avatar
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Question regarding Neel temperature for antiferromagnetic material

I am doing an experiment, where I find that the neel temperature (AFM - PM transition) of a sample is increasing with increase in the magnetic field. Although I tried to find an explanation, I could ...
kvs's user avatar
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Typically, how much could an ferromagnetic core amplify the field of a solenoid?

I have been confused by this for days. Consider a ring-shape solenoid with DC current. If we insert a ferromagetic core (cylinder) into the solenoid, how many time it could amplify the field, compared ...
Lucas's user avatar
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Magnetic field of a magnet bar and the dipoles inside [closed]

The attached picture shows a magnet bar including the green magnetic dipoles inside. In each frame the opposite poles of the two neigbouing dipoles are shown. Can one say that the opposite poles in ...
H. Khani's user avatar
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How do you express the electric and magnetic field of a TEM uniform plane wave due to a magnetic current density?

Given an infinite plane sheet of time-harmonic ($\text{e}^{j\omega t}$) electric and magnetic surface current densitites, $\textbf{J}_{es}$ & $\textbf{J}_{ms}$, respectively, is located in free ...
Rasmus Andersen's user avatar
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1 answer
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Understanding sources (charge and current densities) in Jefimenko Equations

Let's consider the two Jefimenko Equations: $$E(r,t) = \frac{1}{4πϵ_0}∭_V[\frac{e_{r-r'}}{|r-r'|^2} ρ(r',t_r' )+ \frac{1}{c} \frac{e_{r-r'}}{|r-r'|} \frac{∂ρ(r',t_r')}{∂t} - \frac{1}{c^2} \frac{1}{|...
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Is the total magnetic moment of an object equal to the sum of the magnetic moments of the parts that compose it?

For example, given a spherical shell with charge $Q$ rotating on its axis, can I think of it as the composition of many concentric coils and integrate the infinitesimal magnetic moments $d\vec \mu$ to ...
phy6's user avatar
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1 answer
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Why/how is this crumpled wad of aluminum foil exhibiting strong magnetic repulsion against everything?

Forgive the extreme, potentially unnecessary, detail, but I'm trying to include all possible info to account for all possibilities, as this has driven me mad here. I lined a baking pan with Great ...
Foxhole's user avatar
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1 answer
41 views

Is there any tools for observing magnetic fields and forces of black holes and galaxies?

I want to know about how we can find magnetic forces and fields in space around stars, planets, galaxies, pulsars especially pulsars. How (by what means) did determine magnetic fields around a pulsar?
QQQ's user avatar
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How would I calculate the minimum and maximum wavelength of the Bremsstrahlung released by an electron as it goes through a magnetic field?

Say, I have an electron gun and ground below it (with a potential difference of U) and two coils side by side between them producing a relatively homogenous magnetic field B. If I shoot an electron ...
Ominus's user avatar
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-1 votes
1 answer
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How is gradient magnetic field generated in MRI scanner, considering 0 divergence

During the phase and frequency encoding process of MRI scanner, gradient field with a gradient is applied along the direction to change kx and ky of spins at different spatial location. I am confused ...
Yan's user avatar
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Charged particles deflected by gravitational and magnetic fields

I am trying to better understand one of my previous questions, and another. Charged particle in uniform Magnetic field Does a charged particle orbiting Earth radiate? https://en.wikipedia.org/wiki/...
Zoltan K.'s user avatar
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Vector potentials that give monopole magnetic fields with good properties [duplicate]

I am looking for a vector potential $$\mathbf{A}=(A_x,A_y,A_z)$$ giving a monopole magnetic field $$\mathbf{B}=\mathbf{\nabla}\times \mathbf{A}= g\frac{\mathbf{r}}{r^3} = g \left( \frac{x}{r^3}, \frac{...
tony-c's user avatar
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Why does my magnet feel stronger when it is inside it's little metallic cover?

I was recently given a little badge thing to wear to celebrate some event. The badge can be fastened to my shirt using a little magnet. The badge and magnet have since become a little fidget toy for ...
Chechy Levas's user avatar
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29 views

Magnetostatics problem involving dipoles

A while back I came across a problem in which I were to find the force of attraction between a magnetic dipole and a spherical iron ball (which is much smaller than the distance between the dipole and ...
I_am_ant's user avatar
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0 answers
36 views

Outgassing at $10^{-7}$ Torr

I have two iron bars in a vacuum of $10^{-7}$ Torr. One is highly magnetized and the other is not. Will outgassing from the magnetized bar be less than the outgassing from the non-magnetized bar? ...
steveK's user avatar
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Why is 180 degree pulse applied after half echo time (TE) in Spin Echo sequence?

The definition of Echo Time from Radiopaedia: The echo time (TE) refers to the time between the application of the radiofrequency excitation pulse and the peak of the signal induced in the coil. It ...
HelpNeederStudent's user avatar
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36 views

How do "traditional" and Nagaoka magnetism differ in their mechanism

I see that Nagaoka magnetism is a low-temperature quantum effect from "minimizing" the energy of the system, but that explanation, while erudite, doesn't really explore any specifics - ...
user121330's user avatar
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1 answer
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Stoner-Wohlfarth hysteresis at 0 magnetic field

There is something that is confusing me about the Stoner-Wohlfarth model. Looking at the wiki page, one sees this picture for the hysteresis loop: The angles denoted are the angles between the field ...
Andreas Christophilopoulos's user avatar
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1 answer
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How can position of charge moving under magnetic field have different positions for different observers

Assume we have a point charge $Q$ moving with velocity $\vec{v}$ with respect to an observer at rest and is in the presence of magnetic field $\vec{B}$. $\vec{B}$ and $\vec{v}$ are perpendicular to ...
Nipun Kulshreshtha's user avatar
-2 votes
2 answers
87 views

Why is the work done on a particle in a magnetic field zero? [closed]

In the image below, the negative charged particle with a velocity v experiences of force in a magnetic field F perpendicular to the velocity v. The work done on the particle is said to be 0, but why? ...
Yogi Bear's user avatar
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1 answer
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Magnetic mirror and pitch angle of plasmas

I've been learning about magnetic mirrors and how the pitch angle determines whether a particle will be trapped in it or not. I've also learnt about how, when a plasma is trapped, collisions between ...
user374355's user avatar
1 vote
1 answer
48 views

Homogenous magnetic field properties

So I have seen in my uni's notes that if $\vec A = \vec r \times \vec H$ in an homogenous magnetic field then it is $\vec H = \vec \nabla \times \vec A$ , but there is no mathematical or physical ...
Konstantina-Dimitra P.'s user avatar
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Influence of magnetic dipoles on the atomic structure

Niels Bohr in 1922: „Thus LEWIS, who in several respects independently came to the same conclusions as Kossel, suggested that the number 8 characterizing the first groups of the periodic system might ...
HolgerFiedler's user avatar
-2 votes
2 answers
83 views

Does electron moving in a circular motion inside a magnetic field experience acceleration? [closed]

I always thought that object turning means acceleration but what if an electron is caught inside a magnetic field that simply changes it path into a circular one so no electric field is allowed. The ...
user6760's user avatar
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2 votes
1 answer
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When is $\vec D$ or $\vec H$ constant throughout a change in medium?

My question is regarding what happens with $\vec D$ and $\vec H$, when the medium changes, in the case of $\vec D$ when the dielectric changes from $\epsilon_1$ to $\epsilon_0$ or to another $\...
Xetrez's user avatar
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5 votes
2 answers
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Why is there no current in a magnet even though magnetic field is present?

Why is there no current in a magnet even though magnetic field is present? We know current is produced due to magnetic field and vice versa. But there is no current produced in a magnet, why?
Mathematition_From_Wallmart's user avatar
3 votes
0 answers
46 views

Finding the magnetic field from magnetization

with distributing magnetic bipolars in vacuum, we have the magnetization: $$\vec{M}= \frac{a}{\rho}M_{0}\hat{\phi}$$ in the region $0<a\leq\rho\leq b$ , $0\leq \phi<2\times\pi$ , $0\leq z\leq ...
pixiethepixel's user avatar
1 vote
1 answer
129 views

Explanation of the magnetic force in the lab frame

Reasons for the existence of a magnetic force can be found in the rest frame of a moving electron next to a current carrying wire as explained in Chapter 5.9 "Interaction between a moving charge ...
Frank Breitling's user avatar
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1 answer
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Lorentz force separation from induction in rotating loop within AC magnetic field

I was wondering , is it possible to create a loop of any kind of geometry that could rotate in a non homogeneous AC magnetic field and have no net induction within the loop but only have current ...
Girts's user avatar
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Magnets: amplifying a magnetic beam - concern of weakening over time

We have a specific requirement to concentrate a magnetic beam using small Neodymium Magnets. Came across several older threads and within those, an older -now expired- patent: https://patents.google....
George S.'s user avatar
-2 votes
1 answer
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Where is this circular loop attracted? [closed]

A circular loop carrying current "I" in anti-clockwise direction is placed between two straight and parallel wires each carrying current I. Ignoring the force of the straight wires on each ...
Sahaj's user avatar
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Direction of magnetic field, current carrying conductor and its motion

In Fleming's left hand rule, we can see that if current is in direction of middle finger and magnetic field in the direction of fore finger, the thrust must act on the direction of the thumb. These ...
Jithin Sunildas's user avatar
1 vote
1 answer
52 views

Since velocity is a relative quantity, does this mean magnetic force will act as an electrostatic force in a non-intertial frame?

Assume there are two identical bodies (A & B) moving with same velocity, where body 'A' has some non-zero charge while 'B' is electrically neutral. If they come across a magnetic field. 'A' will ...
Ashutosh's user avatar
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