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 ...

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2answers
222 views

Torque per unit length on infinite rotating charged cylinder

For homework I have the following question, but I am stuck on finding the torque on the cylinder. An infinite cylinder of radius $R$ carries a uniform surface charge $\sigma$. We start rotating the ...
2
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4answers
243 views

How any material can provide electrostatic and magnetic shielding

Several metallic objects like Iron, Copper etc can provide electrostatic shielding (one should remain inside the car during thunderstorm) and several superconductors like HTS (High Temperature ...
7
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2answers
821 views

Mechanism by which electric and magnetic fields interrelate

I read that force due to electric field on some particle in one reference frame can exhibit itself as force due to magnetic field in some other reference frame and that electric and magnetic fields ...
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3answers
51 views

Where is the energy stored in an inductor?

In an inductor, Most text books say that the $(1/2)Li^2$ is stored in the magnetic field. But is there another way to explain this? In a capacitor I understand that all the energy that the battery ...
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1answer
21 views

Wireless energy flow through earths magnetic field

Seeing that technologies such as that developed by WItricity are based on magnetic fields, is it possible to transfer electricity that way through earths magnetic field?
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1answer
65 views

magnetic field of a rotating ring magnet

Can the magnetic field of a rotating ring magnet induce current in a conductor? Is there a flux linkage between magnetic field of a rotating ring magnet and a conductor?
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2answers
69 views

Magnetic Field of a Current Loop using Ampère's Law

A typical exercise while introducing the Biot-Savart Law is to calculate the magnetic field caused by a circular current loop at a point P located in its central axis, as shown in the following ...
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4answers
172 views

Do the integral forms of Maxwell's Equations have limited applicability because of retardation?

In the usual bookwork treatment, it is easy to show that the differential and integral forms of Maxwell's equations are equivalent using Gauss's and Stokes's theorems. I have always thought that ...
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2answers
68 views

What physical forces allows for electromagnetic induction

In electromagnetic induction, what force is actually doing the work? what physical force actually drives the electrons around the circuit? Let's say we have a coil and an increasing magnetic field ...
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1answer
27 views

What does an induced emf do to a loop of varying current?

I know that the magnetic flux through a loop in space is proportional to the current such that $\Phi=LI$. Therefore a change in magnetic flux will produce an emf, so $\mathscr{E}=-L\dfrac{dI}{dt}$. ...
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2answers
2k views

Is there a relation between the magnetic field force of the earth and the gravitational force between the earth and other bodies? [on hold]

According to Newton's Universal Law of gravitation, we can say that a huge body of mass will attract another body of mass within a short range, however, if both bodies are for instance magnetic, ...
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1answer
320 views

Coercivity of a ferromagnetic material?

I understand that coercivity is the field/force required to demagnetize/magnetize a ferromagnetic material. What if we had two opposite magnetic fields of different strengths values H acting on the ...
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1answer
60 views

Magnetic flux of a loop due to another loop

The scenario is the following, I am given 2 loops with the same radius, r, a distance of d, and same current of I. In the left loop the current goes counter clockwise, in the right loop the current is ...
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0answers
46 views

Why do we define the magnetic field around a conducting rod as concentric instead of radial?

Why is it that we define the magnetic field around a conducting rod as concentric instead of being radially outwards? Ok, we know from the Lorentz force law, that the magnetic force is the cross ...
2
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4answers
116 views

Faraday's Law - recursive?

So we know that the EMF is induced by change of flux. The thing that was always confusing me is the following: we start changing the magnetic field which in turn induces electric field which makes ...
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0answers
21 views

Ed Leedskalnin's “Perpetual Motion Holder” (PMH)

Edward Leedskalnin (Coral Castle) describes a perpetual motion holder in his writings. I've built one and pretty much know how it works (I think). It is NOT a perpetual motion device by any means, ...
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2answers
74 views

Derivation of Faraday's law using Lorentz force?

For a stationary loop of wire with a time varying magnetic field $\vec{B}(t)$ through it. Is it possible to derive Faraday's law, using only the Lorentz force $$\vec{F}=q \vec v\times \vec B \tag ...
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0answers
15 views

electron trajectory in Bfield with energy kick at midpoint

So I wanted to get some second opinions on this situation I have thinking about.Lets say an electron enters, normally, a section of bfield that is perpendicular to its motion such that the electron ...
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0answers
17 views

Stabilizing the flow of instability [closed]

Where can I find the technology to print in a sphere an unstable pattern of magnetism surrounded with stable magnetism to provoque flow, And the opposite convex ?
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2answers
51 views

How can a magnetic field accelerate particles if it cannot do work?

A varying magnetic field can accelerate charge particles, but it is said that a magnetic field can't do any work so it should be able to speed up charged particles, right? How is this apparent ...
3
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3answers
598 views

How does a magnetic field cause objects to move?

I understand electricity and magnetism and the relationship between them. What I never understood, and never actually seen explained in any book or website, is how opposite magnetic fields cause ...
2
votes
1answer
98 views

Faraday's rotating wire experiment- Can it be explained without using Lorentz force?

I read about Faraday's rotating wire experiment which was the invention of the homopolar motor. He was clever enough to think it that way after observing the behavior of magnetic field around a ...
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0answers
23 views

Defining a gauge field for an anisotropic material under strain

I have a Hamiltonian for a system which is somewhat analogous to graphene but with additional degrees of freedom. The Hamiltonian is $H=\sum_q \Psi^\dagger \mathcal{H}\Psi$ where ...
0
votes
1answer
864 views

How can a magnet have a greater magnetic field strength than a bigger, heavier and more powerful magnet made of the exact same material?

Here are some informations I found on the magnetic field strength (also called "magnetic flux density" or "magnetic induction", commonly denoted as B and expressed in tesla or in gauss) of an average ...
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4answers
4k views

North and south of magnetic field

The current I is flowing upward in the wire in this figure. The direction of the magnetic filed due to the current can be determined by the right hand rule. Can we determine the north and the south ...
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2answers
69 views

Currents induced by rotation of a coil about magnetic field lines

If the coil on the left is rotated about the magnetic field lines, will there be an induced current? I know that the flux concerns only the component of the magnetic field perpendicular to the ...
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0answers
25 views

Change in effective gravity due to a B-field

I have a bar magnet being suspended in a B-field at an angle $\frac{\pi}{2}$ (45 degrees). If I change the frame of reference such that the bar magnet is at 0 degrees I intuitively know that the new ...
3
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4answers
311 views

Magnetic force between two charged particles?

I know the gravitational force between two particles with masses $m_1$, $m_2$: $$ \vec{F} = \frac{Gm_1m_2}{|\vec{r}|^2} \hat{r} $$ And I know the electrical force between two particles with charges ...
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0answers
13 views

How will a single particle move in a curved magnetic field

How will a single iron powder move around the middle of a bar magnet, that is, when the force line is curved? I couldn't figure it out neither quantitatively nor qualitatively since the direction of ...
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0answers
46 views

How does one calculate the applied magnetic strength of a superconductor?

How does one calculate the applied magnetic strength of a superconductor? I spoke with a faculty member about this question. He explained to me that if one can break the spin pairing of two electrons ...
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votes
2answers
148 views

Magnetic field by a solenoid?

I am really not able to understand why is it that the current,while finding the magnetic field in the solenoid (ideal one), is not $I$ the current flowing throught the solenoid but $nI$, where $n$ is ...
1
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1answer
21 views

Flux linkage of 2 coils in series

I have a question from magnetic circuits. I am an engineering student, therefore I will neglect some minor errors. There is a simple magnetic circuit with 2 coils ($C_1$ & $C_2$), with $N_1$ ...
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0answers
32 views

If we put diamagnetic material under strong electromagnet.Would the opposing magnetic fields strong enough to attract ferromagnetic materials?

Suppose we put a diamagnetic material (such as Bismuth or Pyrolytic Carbon) under a strong magnet (see image below). It would create opposing magnetic fields. Would the opposing magnetic field be ...
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1answer
164 views

Why does Earth behave like Natural Bar Magnet?

What is the reason for the Earth to behave like a bar magnet and have poles (North and South poles)?
3
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1answer
445 views

Why is the magnetic field stronger at the edges of a bar magnet?

I have been performing an experiment at school in which I test the force on an iron surface from the magnetic field of an electromagnet. The electromagnet has a rectangular iron core. The theory ...
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1answer
29 views

Given a Magnetic Field vector, what is the Electric Field, charge density, & current density?

I tried searching for this before having to ask, so please forgive me if I missed a previous question similar to mine. This is a Grad class, so I may be unnecessarily too careful in not assuming ...
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2answers
50 views

Divergence of vector potential

I was given the vector potential $$\vec A (\vec r) = - \vec a \times \nabla \frac{1}{r}$$ with a constant vector $\vec a$. Now, I found the $\vec B$ field which is I think $- \vec a \frac{2}{r^3}$, ...
1
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1answer
72 views

Magnetic field of a static disk magnet

I have a magnetic disk (Radius R, height h) that creates magnetic field lines (axisymmetrical). I simulated the field lines, exported the data and am now trying to fit a function into the data to have ...
2
votes
1answer
40 views

If a cube magnet were a die, how would it be numbered?

I have a number of cube-shaped magnets. If I start with 64 cubes all in one long chain and begin arbitrarily "folding over" groups of them so that I am left with a 4x4x4 cube, I rarely get the same ...
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2answers
36 views

What happens to electric field of a bar magnet?

Electromagtic waves say that Magnetic field and electric field exist orthogonal to each other. Also all electric field has some magnetic field and vice-versa (As I understand). In that case what is ...
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0answers
30 views

Why is no work done by magnetic forces in a uniform B and E field (perpendicular to one another)?

Say $B$ points in the $x$ direction, and $E$ points in the $z$ direction. Assuming a charged particle begins at rest at the origin, its motion will be a cycloid that progresses indefinitely in the ...
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2answers
71 views

How to demagnetize a magnet temporarily?

How to demagnetize a magnet temporarily? Is it possible making a permanent magnet demagnetize for a short span of time? Or at least long time but temporarily!
1
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0answers
19 views

Earth's magnetic effect on my magnet

My magnet seems to work independently of, and unaffected by, the Earth's magnetic field, yet the magnetic field of my magnet changes as I introduce some other similar magnets of varied sizes into its ...
0
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2answers
53 views

Why do we lose signal in elevators? [duplicate]

Whenever I am talking on my phone and walk into the elevator the call drops as soon as the doors close, and also the WiFi signal completely stops. Why does this happen? Note: I am asking this ...
1
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1answer
609 views

Force from solenoid

I'd like to approximate the force from a solenoid, or at the very least find a formula which is proportional to the force so that I can experimentally find the constant for my particular case. ...
0
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1answer
49 views

Forces on a wire moving in a magnetic field?

When a wire is placed inside a magnetic field and current starts to flow in that wire, that wire experiences the Lorentz force = $IL \times B$ and beings to move. Aside from induced motional - ...
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1answer
46 views

Can we shield a certain region of space from magnetic field? [duplicate]

Recently I learnt about shielding a region of space from an electric filed. I wondered if the same can happen for magnetic field.
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0answers
9 views

BH Curve of NdFeB Magnet, Grade N50

Every magnet manufacturer provides his own BH-demagnetazation curve of the Neodymium Iron Boron (NdFeB) permanent magnet, grade N50, differently from other manufacturers. Is there a trusted ...
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0answers
14 views

Is there a way to detect acceleration of an object using a magnetic field readings (magnetometer)

I intend to design an application for Android which uses the accelerometer to detect the acceleration. However I'd also like to use the magnetometer to reduce the noise from accelerometer readings. My ...
2
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0answers
68 views

What does the net force do with this droplet in magnetic field?

Consider a spherical droplet with radious $R_d$ which is coated with an immiscible ferrofluid with volume equal to $2v_f$ (shown dark in Fig. 1). While the droplet is in rest on a surface, if I ...