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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 [tag:magnetism], as questions about the phenomenon & theory of magnetism do not necessarily involve the discussion of fields.

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24 views

Symmetry Argument of a Line Charge

I am been trying to make sense of my professor's lecture notes on where he talks about line charges; in general, I am lost when it comes to the symmetry argument in the case that $E_\phi=0$ on an ...
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1answer
28 views

Magnetic fields and electric fields relation [duplicate]

Why do we treat magnetic fields to be different from electric fields?.I thought special relativity had solved this thing.
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2answers
44 views

What causes a magnetic field to be produced at a point in space, when an electric current is flowing nearby?

We know that a current induces a magnetic field along a circular path around it But what exactly causes the magnetic field to produced in that point of space? Is it that change in the direction or ...
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15 views

NMR Bloch equations in 4D?

I'd like to apologize for the purely theoretical question in advance, but I find this an interesting thought-excercise. So basically me and my coworkers asked how the Bloch-equation would look like "...
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10 views

Forces acting on a charged particle [on hold]

List down the forces that act on a charged particle when, a) it is at rest and b) it starts to move.
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1answer
30 views

How does an electrical field influence a changing magnetic field?

I would like to know what happens in the following situation. (I am not planning on actually doing this - I just want to understand). Suppose I have a permanent magnet contained in a plastic capsule, ...
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10 views

Can we get energy from alternig locally the earth's magnetic field? [on hold]

Is it possible to create energy alterning between a state in which one system is under the influence of the earth's magnetic field and one in which it is isolated from it? Would it take more energy to ...
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0answers
19 views

Solenoid type Conductor [on hold]

A long hollow cylindrical conductor of length L and small radius carries total current I along its curved surface as shown in figure. The magnetic field inside the cylinder is I tried this question ...
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28 views

Magnetic field inside hollow cylinder [on hold]

A hollow thin walled conducting long cylinder of radius $R$ is carrying current I along its length. A thin slit of width $h$ is cut along the length of cylinder. What is the magnetic field just inside ...
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A doubt and different approach regarding “A hypothetical magnetic field existing…”

A popular question from the book HC Verma's Concepts of Physics goes like this:- "A hypothetical magnetic field existing in a region is given by $$ \vec{B}=B_{0} \vec{e}_{r} $$ where er denotes the ...
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27 views

Is the calculation of $\mu_0 \cdot M$ = Tesla valid?

in the Paper "Static Stern-Gerlach effect in magnetic force microscopy", they estimate: $$\mu_0 \cdot M= 1 \text{ T}$$ with $\mu_0$ in H/m which is the permeability of the free space, and $M$ is the ...
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Scalar Potential Boundary Conditions in Magnetic Diffusion

The magnetic diffusion equation, $$ \frac{1}{\mu\sigma}\nabla^2 \vec{H} = \frac{\partial \vec{H}}{\partial t}, $$ in one dimension is written, $$ \frac{1}{\mu \sigma} \frac{\partial^2 H}{\partial x^2} ...
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Magnetic field “lines” in $D \ne 4$ spacetimes

The electromagnetic field is represented by an antisymetric tensor $F_{ab} = -\, F_{ba}$ (the faraday). In $D = 4$ spacetimes, it has 6 independent componenents: 3 describing the electric field: $F_{...
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2answers
60 views

Does the spin has a determinate value in magnetic field?

Consider a 1/2 spin particle like proton in magnetic field $B$ in the $z$ direction with strength as high as in NMR appliances. Then the anomalous Zeeman Effect occurs. And the particle has two ...
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Power absorption - ferromagnetic resonance

Magnetic energy is given by: $$ E(t) = \mathbf{M}(t)\cdot \mathbf{H}(t)$$ Hence, the magnetic power becomes: $$P(t) = \mathbf{M}(t) \cdot \frac{\mathbf{H}(t)}{dt} + \mathbf{H}(t) \cdot \frac{\mathbf{...
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1answer
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Same length insulated wire small gauge vs larger gauge

I'm doing an school experiment with my daughter and I made two alternating current generators. One is a coil of 22 gauge wire and the other is a coil of 28 gauge wire where we rub a strong block of ...
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0answers
24 views

What shapes could we theoretically make a plasma window? [closed]

I have been reading up on the plasma window, originally discovered by Ady Hershcovitch. A copy of his original paper can be found here. Essentially it has been shown that plasma arcs can be used to ...
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1answer
24 views

Is it possible to change the direction of magnetization of a magnetic sheet?

I want to try an experiment where I have to attract or repel thin sheets of material using an electromagnet. I have found lots of magnetic sheets for sale, but all of them are magnetized so that the ...
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1answer
59 views

Does a time-varying magnetic field ALWAYS produce an electric field?

Assume two similar point charges located a distance $\Delta y$ away from each other are set in motion with the same velocity $v$ in opposite directions as shown in the figure. The lab observer located ...
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1answer
21 views

Drone's sufficient engine RPMs initiated by Magnetic Fields

I've seen many videos where magnets are used to initiate and boost RPMs. Most of them are fake, where people are using compressed air at the backstage. Did anyone of you actually tried to challenge ...
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2answers
20 views

Could a disturbance to a magnetic field be detected near the source?

(Forgive my crude MS paint drawing) Imagine we have a large magnetic field coming from a powerful source. At the edge of the field where it is weak (A), we introduce a disturbance using another ...
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0answers
25 views

Eigenstates in a 2D metal disk with finite-size perpendicular magnetic field (Piece-wise Gauge)

Let's have a two-dimensional metal disk with radius R, and now I apply a uniform magnetic field B perpendicular to the disk, within the concentric part of the disk with radius r $\lt$ R. How can we ...
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Screened magnetic interactions

I hear all the time people saying magnetic interactions are not screened. I do not understand what it means. Is it related to the nonexistence of magnetic monopole? I assume you can always find some ...
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Will a magnet diffuse/defocus a laser?

I have read through hundreds of questions here and we discuss why light is not bent by an electric or magnetic field (at least not at easily visible levels in the classical sense), but that there is ...
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0answers
25 views

How to do colour map in MRI?

For this question, I assume if we do a colour map, it is based on the magnitude of the magnetic strength? After that how do we know where each coordinates belong to? Like for example at p= 0 degrees,...
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1answer
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Is it possible to measure the amplitude of a magnetic field independent of the orientation?

The strength of a magnetic field can be measured as strength in a specific direction. We can calculate the strength of a magnetic field along the field lines from measuring the strength in x,y,z ...
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4answers
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Can a magnet bend light? [duplicate]

As light is electromagnetic radiation. Then why I don't see any magnet bending light wave? Or why light doesn't diffract whenever it passes by a live wire?
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3answers
56 views

Why the magnetic field is perpendicular to the electric field?

I am a high school student. Recently I have read about magnetism. Each time I found magnetic field has to be perpendicular with electric field. Is there any explanation why is it?
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1answer
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Neutral hydrogen atoms in inhomogenous magnetic field

In the 1996 gre exam this scenario comes up in a question: a beam of neutral hydrogen atoms in their ground state pass through a region of of strong inhomogenous magnetic field. In the official ...
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2answers
63 views

Can a moving current carrying wire produce electric field?

As we know, a current carrying wire can create a magnetic field which is perpendicular to the direction of current (From relativity, we can understand why magnetic fields are produced ) and the net ...
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3answers
145 views

Stumped on understanding a Feynman lecture about force from wire on magnet

I must (sheepishly) admit that I'm stumped on a beginning page of The Feynman Lectures Volume 2. I have included a picture from the page. [Let me know if I'm breaking copyright, or if I can include ...
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4answers
102 views

Does the magnetic part of the Lorentz force do work?

The magnetic part of the Lorentz force is $$\vec F_L=q\left(\vec v\times\vec B\right)$$ As this force is always perpendicular to the direction of the movement, we learned that no work is done by it. ...
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1answer
33 views

Can a spacecraft be sent into orbit using magnetic propulsion?

Can a rocket potentially be sent to orbit using magnetic force? For example, If I attach two powerful magnets to a light spacecraft, will the resulting magnetic force be enough to move it?
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How to imagine the magnetic field resulted from current passing through circular coil?

are there any rules that can help you the imagine the magnetic field due to current passing through circular coil ? like the right hand rule which is used for determining the direction of magnetic ...
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1answer
18 views

If a metal rod of length l is moved perpendicularly, in a straight line, inside a uniform magnetic field, will a emf be induced in the rod?

The magnetic flux density is constant, and the rod is being moved inside the field. And if an emf is induced, how does the flux linkage change in this rod? The cross sectional area of this rod ...
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0answers
9 views

Metal Plate will not lie flat in a magnetic field created by Helmholtz coil

I am trying to make an EM field to do non contact compression. I have wound to Helmholtz coils and threw in a gray iron cores in both to try and increase the field strength. The coils have a 60mm ...
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0answers
27 views

Achieve geosynchronous orbital speeds at leo while moving relative to a electric field

Would it be possible for an object to move at geosynchronous orbital speeds at LEO? Assume that a superconductive ring extending around the entire Earth existed at the same height as the ISS. Could an ...
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4answers
100 views

3 Dimensional Law of Cosines? Magnetic Vector Potential Problem

I am working on a problem similar to one in my textbook - however, I am having an issue understanding the example. Can someone explain the formulas from this picture? I am confused about using the law ...
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1answer
20 views

How to stabilize magnetic fields in/around electron microscope?

Let us assume we have a very strong electron microscope. One that would need multiple electro-static and electro-magnetic lenses. The electrostatic lens is used to accelerate the electrons to a ...
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1answer
59 views

Surprisingly Uniform Magnetic Field inside a Rotating Charged Sphere

Consider this: A spherical shell of radius R, carrying a uniform surface charge $σ$, is set spinning at an angular velocity $ω$. What can be said about the magnetic field inside the sphere? I ...
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0answers
13 views

Electromagnetism question about the magnetic flux and inductance of a parallel wire transmission line

I derived using the formula for the magnetic field of an infinite wire that the flux between the wires is the same as that in the answer but with $b-a$ on top. This is because when you integrate $B\...
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1answer
30 views

How to determine the magnetic permeability of an area containing multiple substances

So I'm trying to determine the magnetic permeability of an area that contains multiple substances. let's say i have some volume $V$ that is filled with two substances, one is iron filings and the rest ...
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0answers
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How do you apply “flux-rule” in free space?

Faraday's law of induction states that, the tangential component of the force per unit charge$^*$; EMF produced in a loop of wire, is equal to change in the magnetic flux through the loop, $$\int_C \...
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14 views

diamagnetic substances and experimental support of electron configuration

In a basic explanation I have read regarding apparatus used to show the electron configuration of a material's atoms, it states that diamagnetic substances when weighed in the presence of an external ...
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1answer
33 views

Force acting on a current carrying hollow conductor within a magnetic field

It is known that when a current carrying conductor is placed within a magnetic field and current flows perpendicular to the magnetic field, a force is exerted on the conductor. In figure 1, a square ...
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0answers
15 views

How should I express the force field acting on a ring in Thomson's jumping ring experiment?

I did Thomson's Jumping Ring Experiment with some additional factors added. I used aluminium rings of the same inner diameter, same thickness (at 2 mm), but varying outer diameter (starting from 65 mm ...
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2answers
56 views

What is providing the force required to move the conductor in a changing magnetic field?

Earlier, I came across this problem. It goes as, "The current in the long wire is suddenly switched off. Neglecting gravity, what is the velocity acquired by the loop" Attached figure: Now, my ...
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0answers
18 views

Proof that $\text{Magnetic Flux Density} = {\text{Magentic Flux} \over A\sin(θ)}?$

Problem : How is $\text{Magnetic Flux Density} = {\text{Magnetic Flux} \over A\sin(θ)}$ (this is the formula my text book has given me) Where $θ$ is the angle between magnetic flux lines and plane ...
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2answers
41 views

What really is an electric/magnetic field?

Have you ever wondered how we can see this field or how it's formed its shape in space? I know we can feel that there's one by its effect which is the force. But what does it look like? We all know ...
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1answer
55 views

Why aren't primary and secondary coils of a transformer overlapped over each other? [closed]

I am aware that soft iron core present in a transformer does prevent flux leakage. But practically there is some non-negligible flux leakage nonetheless. Why not then just overlap the coils over each ...