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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36 views

What happens if I have a square conducting wire being permeated by a magnetic field and the field suddenly disappears?

Suppose there is a square conducting wire in a magnetic field. The two vertical branches will have the same emf, and the two horizontal branches will have 0 emf, resulting in a net emf of zero and ...
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0answers
8 views

How to get image current in magnetostatics? (magnetic slab)

I want to know the image current and its location which satisfies the boundary condition at the interface. This problem was originated from the problem 6-33 in Fields and wave electromagnetics, D. ...
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1answer
15 views

Moving coil through space

Programmer here, I have simple question about existence of magnetic field relative to the coil, when moving in space. Imagine we have coil L, that is connected to battery / power supply and coil is ...
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0answers
21 views

Magnetic field at focus of parabola [on hold]

A parabola in $x$-$y$ plane carries current $I$, find the magnetic field at the focus of the parabola. Assume focus is at the origin and the focal length of parabola is $d$.
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2answers
34 views

Force on non-moving charge in solenoid with increasing magnetic field

The problem: "Through a solenoid there is an increasing magnetic field $B$. For a positively charged particle not in motion, what is the direction of force on the particle?" Normally a non-moving ...
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0answers
18 views

Books of dynamo theory

I wanted recommendations of dynamo theory pdfs to make a report about magnetic fields of planets and stars with all the math behind it, like vector calculus, Lagrange functions, partial differential ...
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4answers
58 views

Why does a current-carrying conductor behave like a magnet?

I have heard that a current-carrying conductor behaves like a magnet, the reason why the magnetic needle of a compass kept near the circuit, deflects. Why is it so?
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1answer
33 views

Can the magnetic force between two magnets be explained classically via magnetization current?

Usually in Electrodynamics courses the magnetic forces are analysed via wire-wire interaction. I don't remember being shown a classical explanation for magnetic forces between magnets. Since it is a ...
2
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1answer
38 views

Will two opposing magnetic fields cancel out?

When a conductor induces eddy currents that creates a magnetic field opposing the change that created it, would the two fields at some point cancel out? Imagine the change to be so great, it ...
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3answers
40 views

Zero current induced in a loop

Consider the following two cases, Case 1 – A coil moving through a constant magnetic field Case 2 – A conductor moving through a constant magnetic field Now, in Case 1 (a coil moving through a ...
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2answers
32 views

Which centripetal force equation should I use for centripetal motion in uniform magnetic field, and why?

So far I learn two equations, doing the same thing: $$F_c = m\frac{v^2}{r} = qvB$$ It leaves me undecided when a question asks "by what factor is the force increased when velocity is double". The ...
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1answer
43 views

How can the magnetic field surrounding a current-carrying wire ever be uniform?

My book says that to find the force a current-carrying wire exerts on a moving charge, one uses $B = (\mu_0 / 2\pi)(I/r)$ to find the magnitude of magnetic field around the wire, and then uses that to ...
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1answer
19 views

magnetic intensity of cylinder sheet of charge having surface charge density K

Here is the problem I have by using $$a_z\times R = (0,0,1) \times (\rho-1.2,0,-z) = (\rho -1.2)a_\phi $$ $$H=\int_{-\infty}^{\infty}\int_{0}^{2\pi}\frac{2.4(\rho-1.2)d\phi dz}{4\pi ...
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2answers
35 views

What sources of magnetic fields in urban society are strong enough to lure a compass off north? [on hold]

I'm writing about the usage of magnetometers in navigation applications. As part of my reasoning about why you should be careful with it's usage (I've shown in experiments that some environments bring ...
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1answer
27 views

Already integrated formula of magnetic field for a finite line?

I was looking for a formula to simulate a magnetic field due to a straight finite line. The closest to what I wanted to find was in these lecture notes (formula 9.11.2 page 9-50), \begin{align} ...
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0answers
16 views

Do lightening strikes permanently magnetise metallic objects?

Has it been proven yet that lightening can permanently cause magnetism? If so, do all the high rise buildings have their lightening rods magnetised after every strike?
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2answers
41 views

Do permanent magnets have an electric current surrounding them?

Permanent magnets seems to have different properties to electromagnets, such that electromagnets can be used for induction and energy transfer if a conductor is placed within their changing magnetic ...
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1answer
32 views

Motional EMF and Conservation of energy

Consider a conducting rod moving in a uniform magnetic field $\vec{B}$ with a uniform velocity $\vec{v}$. According to the theory involved, the electrons experience the magnetic force ...
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4answers
74 views

Positive work by a magnetic field

Consider a single charge moving only under the influence of Magnetic Field $\vec{B}$. The charged particle moves in a circle and the work done by $\vec{B}$ is 0. Now consider a current element in a ...
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4answers
242 views

What is the *cause* of the Lorentz Force

Is it possible to explain what actually causes the force on a current carrying conductor in a magnetic field. I have read that this is due to the magnetic fields 'interacting' in some way. This ...
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0answers
27 views

How much energy is in a refrigerator magnet? [duplicate]

I used to contemplate a machine that would spin via the push of a magnet - not an uncommon idea I found - but apparently magnets dont push forever so no perpetual motion machine. But that got me ...
1
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1answer
67 views
+50

Prove that Laughlin's 3-electron states are a complete set of states

In R. B. Laughlin's 1983 Physical Review B article, Quantized motion of three two-dimensional electrons in a strong magnetic field, Laughlin separates out the center of mass motion of the electrons, ...
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1answer
29 views

How does a magnet cause magnetic force and its magnitude/direction?

Magnetic fields are created due to electron spin in the magnet. But how exactly does an electron "spinning" create forces around the magnet? Also, the magnetic force on a charge moving in the magnetic ...
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0answers
29 views

Can current be stopped using magnetic field?

Is it possible to stop a current "running" through wire only by using a magnetic field around the wire?
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0answers
37 views

Magnetic field on axis of solenoid

So first I'd like to say that I have asked similar questions to this one. However, all the answers involve a level of calculus that I do not yet know. (Still on limits, going to spend the rest of ...
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1answer
33 views

Magnetic field re-routing

Can a magnetic field be directed in a particular direction, that is re-route it, such that the magnetic field comes out in only one direction?
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1answer
51 views

What are the interpretations of ampere's circuital law for a single moving electron?

I understand from Ampere's circuital law that when a current passes though any open surface with a boundary (a circular boundary, for simplicity), then limit of summation of the scalar products of ...
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0answers
28 views

Quantity of force between two magnets

I have compiled data detailing a magnetic field. If I assume a duplicate magnet is set up across from it, how can I calculate the repulsive force between them?
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1answer
30 views

Does a magnet become less of a magnet if used to magnetize another piece of metal

If you run a magnet a few times over an unmagnetized piece of a magnetic material (such as an iron nail), you can convert it into a magnet as well. Will using a permanent magnet to magnetize something ...
3
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2answers
109 views

How can magnetic fields have energy and yet be unable to do work with that energy? [duplicate]

Magnetic fields can't do work. However, we use the following equation to describe the energy density of a magnetic field. $u = \frac{B^2}{2\mu_0}$ The term energy density suggests that the magnetic ...
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0answers
24 views

Magnetic field due to current carrying sheet

I have 2 infinite plates (x direction) with the width of A (y direction) and the distance between them is d (z direction). The current density is J on the first plate and -J on the second (the ...
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0answers
53 views

How it is predicted, that a moving charge has to have a magnetic field?

This question appears after this comment: Even electric charges without intrinsic magnetic dipoles moments produce magnetic fields when they move. My respons: All electric charges (electron, ...
3
votes
4answers
91 views

How does an inductor store magnetic energy?

I am trying to figure out what the potential energy of an inductor with a current really means. In a capacitor, the energy stored works like this: if you let the plates attract each other, before ...
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1answer
34 views

If we were to observe a cluster of planets from a star's magnetic north, which direction would they appear to orbit? Clockwise or counter clockwise?

I have a question, and it's been a topic of great discussion amongst my peers. If we look at galaxies or clusters of planets around stars, they appear to be moving both clockwise and counter ...
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1answer
38 views

Force of electromagnet on a wire [closed]

I'm trying to produce an equation for the force produced by an electromagnet on a wire. I'm very aware I don't know any vector calculus but I think as it's the special case (Perpendicular) I can just ...
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0answers
17 views

Off-axial Field of Finite Solenoid

Regarding the computation of the off-axial field of a finite solenoid: The Radial and Z components of the off-axial magnetic field of a solenoid are given as: \begin{align} B_r &= \frac{\mu ...
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2answers
57 views

Concept of a Magnetic Field

I was reading a physics book by some author and I got a little too confused with the explanation he stated about magnetic fields. A magnetic field is a field of force produced by current-carrying ...
0
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1answer
46 views

Fringing effect of electric current

We know the what is the fringing effect of electric field in capacitor, of magnetic field in some in some solenoid or magnetic field in through joint of some metal. But is there is something similar ...
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0answers
28 views

A magnet floating due to Meissner effect

If a magnet is floating due to the Meissner effect, can the magnet rotate freely under influence of external field in spite of the presence of north and south pole in it ?
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0answers
21 views

surface current density

Surface current density, K is defined as: K = σv where σ is surface charge density and v is velocity. Given a uniformly charged spherical shell with radius R, spinning at constant angular velocity ω, ...
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0answers
57 views

$E$-field from changing current in straight wire

A very long insulated wire oriented along the $z$ axis of a cylindrical coordinate system is carrying current that is defined by the following function: $$I(t) =Io + k⋅t$$ (current increases linearly ...
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0answers
45 views

Regarding Ampere's Circuital Law

If I am to show that Ampere's Circuital law holds true for any arbitrary closed loop in a plane normal to the straight wire, with its validity already established for the closed loop being a circle of ...
0
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1answer
18 views

$H$ field from corresponding $E$ field (antenna)

The $E$ field at $kr >> 1$ due to a short dipole oriented in the $z$-direction and located at the origin is: $$E_0 = \frac{10^3e^{-jkr}}{r}\sin\theta\space\space(V/m)$$ Can I just solve for the ...
1
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1answer
35 views

Dependence of Hall coefficient on temperature in copper

As part of a project on the Hall Effect in metals, we would like to find out whether the Hall Coefficient of copper depends on its temperature, and if so how. We passed a current I through a copper ...
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2answers
92 views

What is the secret of this perpetual motion machine with neodimimum magnets?

The following device is apparently based on magnetic forces only and has no visible energy source: Where is it's energy source? Full video: http://www.youtube.com/watch?v=eA0b-8pqUCk UPDATE One ...
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0answers
46 views

Adding Magnetic Fields?

Ok, so we all know that the strength of a magnetic field can be increased if a wire with current flowing through it is surrounding the magnet. Because the current flowing through the wire is making a ...
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2answers
80 views

Magnet dimensions for 3-phase permanent generator

I'm making a 3-phase permenant generator. According to Faraday's law, the emf produced is negative number of turns times the change in magnetic flux over the change in time. If it is only the CHANGE ...
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2answers
66 views

Particle beam in infinite magnetic field

In a physics exam at university I had the following problem: A proton-deuteron beam is accelerated by a $\Delta V = 10^7\,\mathrm{V}$ difference of potential. At some point, the particles enter ...
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0answers
29 views

Magnetic levitation project

For the past four years, I have been working on a project that will allow permanent magnets to levitate stably above a magnetic surface. So far I have tested my first theory which was to see if ...