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.

Filter by
Sorted by
Tagged with
0
votes
0answers
12 views

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 ...
2
votes
0answers
40 views

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_{...
1
vote
1answer
164 views

What would happen if a magnet was pushed towards a copper tube in space?

So the question was inspired by one of curious comments on youtube. What exactly would happen if you pushed a strong neodymium magnet towards the copper tube (aiming for the opening in an effort to ...
0
votes
0answers
23 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 ...
0
votes
1answer
32 views

Does the spin has a determinate value in magnetic field?

Consider a 1/2 spin particle like proton in magnetic field B in z direction with strength as high as in NMR appliances. Then the anomalous Zeeman Effect occurs. And the particle has two possible ...
0
votes
0answers
9 views

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} ...
0
votes
2answers
353 views

Faraday's law and motional EMF

My understanding of motional EMF is that one of the ways it is created is by moving a conductor (moving such that its orientation doesn't change) in a uniform magnetic field (non changing). EMF is ...
0
votes
1answer
248 views

Long Current-Carrying Solenoid

Why is the magnetic field inside a long current-carrying solenoid does not depend on distance from the axis?
0
votes
1answer
41 views

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 ...
4
votes
3answers
143 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 ...
3
votes
0answers
171 views

Which part of a real Type II Superconductor magnetization loop represents the Meissner state?

So if we consider an ideal type II superconductor the magnetization should look like this The Meissner state is to be found between $0$ and $H_{c1}$ and the superconductor works as an ideal diamagnet ...
0
votes
0answers
6 views

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{...
0
votes
2answers
197 views

How does Lenz law conserve energy in this case?

A magnet is falling into the coil as shown. The current in the coil creates a magnet as shown ( by the right-hand grip rule ). Now, as the magnet falls towards the coil, the magnetic field strength in ...
0
votes
1answer
23 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 ...
0
votes
1answer
57 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 ...
-1
votes
0answers
24 views

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

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 ...
0
votes
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 ...
2
votes
2answers
153 views

Magnetic levitation against Earnshaw's Theorem?

Given six strong magnets, what if we fix three of them to a table in a simple, horizontal, equilateral triangle-like formation (with their north poles sticking up), and the other three to the points ...
0
votes
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 ...
2
votes
0answers
24 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 ...
0
votes
0answers
3 views

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 ...
8
votes
4answers
1k views

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?
-1
votes
1answer
25 views

Motion of magnetic dipoles in electromagnetic fields [closed]

Please can anyone tell me the: 1) motion of an electric dipole in uniform electric field 2) motion of an electric dipole in non uniform electric field 3) motion of a magnetic dipole in uniform ...
-1
votes
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,...
1
vote
0answers
14 views

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 ...
0
votes
1answer
15 views

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 ...
1
vote
2answers
164 views

Magnetism in different reference frames

Moving electric charges produce magnetic fields. As explained in this great Physics.StackExchange answer, we can think of magnetism as simply electrostatics combined with special relativity. My ...
0
votes
2answers
457 views

Vector Potential of a rotating Spherical Shell

I have done all the calculation in finding the vector potential leading up to the equation 5.68. But then Prof. Griffiths goes back to the original figure and mentions that the coordinate of the point ...
1
vote
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 ...
1
vote
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 ...
0
votes
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?
0
votes
1answer
10 views

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 ...
1
vote
4answers
99 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. ...
0
votes
1answer
322 views

Deflection of compass and rest position through Magnetic induction

I found a problem with a compass and a magnet, as diagrammed below. The needle of the compass was oscillating, but when a soft iron bar was placed in the “X” then the needle came to rest. Why did ...
0
votes
1answer
173 views

Magnetic field and electric field close to small signal audio

I have built a very compact tube amplifier. I have a $6$ V AC / $3$A supply powering the vacuum tube heaters. The 2 wires (positive & return current) are very close to the input. The input ...
0
votes
1answer
155 views

General Question about Faraday Disk and a Loop

If we have a constant magnetic field, $B$, perpendicular to a rotating metal disk (essentially Faradays's disk), with some angular frequency, $f$ . Then there will be an emf across the ends of the ...
0
votes
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?
0
votes
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 ...
0
votes
0answers
7 views

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 ...
0
votes
0answers
8 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 ...
3
votes
1answer
57 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 ...
0
votes
5answers
846 views

Why does more rapidly changing magnetic field induce greater EMF?

I am confused about the above question. I know that when you move a magnet in and out of a close loop of wire, you induce a EMF in the wire. The change of moving the wire in a out of a wire is what is ...
0
votes
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 ...
0
votes
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 ...
0
votes
1answer
182 views

What can be done to increase the strength of a given electromagnet?

There's a lot of information online about increasing the strength of an electromagnet with more turns, different cores, etc, but not much about factors in the power supply that affect the strength of ...
0
votes
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 ...
0
votes
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\...
1
vote
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 ...
2
votes
0answers
20 views

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 \...
0
votes
0answers
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 ...