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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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How could you protect electronics from 100-1000g of acceleration [on hold]

I am currently researching the feasibility of setting up a coilgun that launches Cubesats for a paper.
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1answer
12 views

About Supercurrent Direction in London Theory of Supercondutivity

I'm studying superconductivity starting from London's approach. After you obtain the two London's eqs you get for the static case: $\quad \nabla^2 \textbf{B}=\frac{1}{\lambda_L^2}\textbf{B}$ If ...
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1answer
35 views

Electrons in an Inductor

What basically happens to the electrons, does the magnetic field produced by the electron moving in the inductor affect itself. what are the forces involved? Please elucidate the mathematics. The ...
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1answer
15 views

What is the flux $\Phi$ enclosed by cyclotron orbit, which can express the quantization rule?

Suppose an electron (mass $m$, charge $e$) in the xy-plane with $B=(0,0,B)$ (The classical EOM result in circular orbit). Using the Bohr-Sommerfeld quantization rule we can find that $E_n = (n+1/2)\...
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If is work done by magnetic field is 0 then why does 2 magnets attract when kept together? [duplicate]

If 2 magnets are kept close to each other they attract then shouldn't it be considered as work done by magnetic field?
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3answers
45 views

Explanation of Lenz's Law phenomena

If we drop a magnet through a copper pipe (without it touching any of the sides), it would fall slower than it would if there were no pipe. Having the pipe otherwise accelerate the magnet would be in ...
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3d transition metal atoms magnetization

When trying to characterize the magnetic nature of different atomic elements, 3d transition metals have stood out in a few papers that I have read but I still have a few questions about them. As I ...
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1answer
42 views

Sliding rod in magnetic field with two loops

The circuit is concatenated with a constant flux $B$ and the rod slides with constant velocity $v$. Find the current through the rod. Before I always solved the problem without the resistor $R_2$ by ...
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10 views

Can a magnetic field's orientation be transported?

The question might be formulated completely incorrectly, but the essence is : Is it possible to have a magnetic fields orientation be transported across a material, so that you can measure the fields ...
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1answer
32 views

Magnetic field around solenoid and toroid

Solenoid is proving a little bit confusing While getting through solenoid I found that the field outside it is extremely small and is negligible. Also the field at ends is half of that of center. ...
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1answer
26 views

Vector Poisson Equation for a symmetrical geometry

I was recently doing some simulations involving the vector Poisson equation and symmetrical geometries with respect to one plane. My question is basically if the computations involved can be reduced ...
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1answer
49 views

Can I replace a multipole expansion by a combination of separate dipoles?

If I want to be able to model a magnetic field flux density $\mathbf{B}$ from a magnetic source located at the origin at a position $\mathbf{r}$, it is my understanding that I can represent $\mathbf{B}...
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The solenoid and toroid a little bit confusing

While studying solenoid I came across the different arrangement of field lines around and inside it I was wondering why the field lines are parallel and uniform inside it but very far apart outside ...
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1answer
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Deducing the direction of the magnetic vector potential from its curl

We have an infinite cylinder of radius $a$ around the $z$ axis. The current density inside the cylinder is uniform: $\vec J=J_0\hat z$. We wish to find the magnetic vector potential $\vec A$ (though I ...
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2answers
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How would a moving charged particle react within a parallel arrangement and conical arrangement of magnetic fields?

I am very interested in finding out how a moving charged particle would react if it were to enter into an area with parallel magnetic fields and also if it were to enter into an area with conical ...
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6answers
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Permanent Magnetic Field vs Electromagnetic Field

If I put a permanent magnet under a box and an energized electromagnetic coil under another box could you tell me which box was covering the permanent magnet? If the answer is yes what test would you ...
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1answer
49 views

Properties of magnetic field [closed]

While studying magnetic field and electric field I encounter the following properties of it for which I need an explanation as what they mean. magnetism is relativistic magnetic field has ...
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1answer
31 views

How to find the direction of the magnetic field [closed]

When I was reading the chapter of magnetic field I got to know about the direction of the magnetic field around current carrying various shapes but I was confuse there as in some cases the direction ...
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0answers
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How/Why does this happen in this toy? [closed]

I made this spring action toy using magnetic balls (called neocubes) accidentally some time ago. But I do not understand the Physics behind it. Why won't the middle ones stick?
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1answer
25 views

Potential energy of a charge in a magnetic quadrupole field

I have a charged particle of charge $q$ that moves with velocity $\vec{V}$ from a position $\vec{r}$, inside a magnetic quadrupole field of the form: $$\vec{B}=B_{0}(x,y, -2z)$$ The Lorentz force acts ...
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1answer
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How does this magnetic toy work?

A nephew of mine has this toy called "Gravitrax". It is basically a track building kit - you can build various tracks for iron balls which go through the track thanks to gravity. However, there is ...
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3answers
46 views

What do the magnetic fields lines produced by a solenoid made out of another solenoid look like?

Suppose we take a solenoid: I was wondering what the magnetic field pattern would look like if the black current-carrying wire in the depicted solenoid was replaced by a solenoid. In other words, ...
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2answers
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Which Pole on a Magnet actually exerts the tension?

My questions is on magnets, is the north pole being attracted to the south pole or is the south pole attracted to the north. Basically I am thinking as magnets as 2 pieces of matter with a tension ...
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0answers
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Calculate the magnetic field of 2 circular conductor wires, [closed]

Calculate the magnetic field from 2 circular conductor wires, where the inner wire has radius A and the outer wire has radius B. Both are different types of wire and also have different currents. ...
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0answers
48 views

Everyday magnetism as a consequence of perfect balance of electrical effects

Consider two charges moving in space, both at the same speed and parallel to each other. Because they are moving, they will behave like two currents and will have a magnetic field associated with ...
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0answers
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why doesn't EM waves get weaker as we travel further away from the source [duplicate]

I know that as we get further away from the charge or from the magnetic field source both magnetic field and electric field decreases ,so why don't electromagnetic waves get weaker as the travel ...
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3answers
74 views

Divergence of magnetic field

Consider a point near one of the poles of a bar magnet. The magnetic field lines do appear to spread, but according to Maxwell's equations the divergence of a magnetic field is always zero. So what's ...
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2answers
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The form of $H$ in a bar magnet

The magnetic field strength, H looks very different inside a bar magnet as shown below I have two main questions regarding this, why can we regard ‘magnetisation poles’ as the sources of H. When I ...
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1answer
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Can't Determine the direction of rotation of a coil

Speaking of coils and torque here, So I have a coil and after I did fleming's right hand rule to get the direction of the torque (let it be the positive x-axis unit vector î can't remember it ...
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1answer
44 views

Interaction of three electromagnets placed in a row [closed]

I'm trying to solve a practical problem, as follows: I want to make a system that consists of three electromagnets arranged as in the picture. The two side ones can’t move, but the middle one can. ...
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1answer
29 views

Is there a minimum field required in order to start magnetizing an initially unmagnetized ferromagnet?

The question Would a compass with unmagnetized needle work? never seems to have been resolved, due to getting bogged down in a number of sub-issues where different people made seemingly contradictory ...
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1answer
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Radon / Alpha / 100s of bar magnets - To what degree are large bar magnets affecting the concentration of alpha particles? [closed]

A guitar pickup magnet is a bar magnet with about 60-100, sometimes 250 gauss. Each pickup has 1 magnet. At our shop, we have about 200-300 pickups all in a concentration of one room. These magnets ...
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0answers
25 views

Magnetic field at the center of a rotating charged square loop

Consider a square loop of side length $2a$, with a total charge $Q$ uniformly distributed along its sides (so that the line charge density is $\lambda=\frac{Q}{8a}$), set spinning at angular velocity $...
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0answers
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Magnetic field intensity H and Magnetic field density B

Standards Organizations have recently moved to magnetic constant as the preferred name for μ0, although the older name continues to be listed as a synonym. Historically, the constant μ0 has had ...
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4answers
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Would a compass with unmagnetized needle work?

We know that the needle that is used in a compass is a permanently magnetized ferromagnetic material and commonly steel is used. If we used an unmagnetized iron needle instead, would it still align ...
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0answers
10 views

Why does semimetals (particularly nearly compensated ones) have very strong magnetoresistance?

It's well established that semimetals, i.e. metals with both electrons and holes, have a strongest enhancement of its resistance when subject to a magnetic field (namely magnetoresistance). From the ...
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1answer
33 views

Meissner effect

Meissner effect Why do field lines again get back to straight line after getting deflecting during superconducting state?
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1answer
31 views

How can Resistance be transferred across in a Transformer?

Can someone tell me how the resistor could be transfered from the secondary to the primary side? Could you give me a concise explanation on how it's possible? A simple analogy/analysis would be very ...
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0answers
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What's the explanation for Kohler's rule?

In a metal, the increase of resistivity ($\Delta\rho$) due to an applied magnetic field follows a functional form of the parameter $\rho_0/B$ (residual resistivity divided by magnetic field) i.e. $$(\...
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1answer
40 views

Why this transformer have different power input & output?

Assume an ideal transformer with the same number of windings, the primary windings generate 50VAC, 10Amps (5Ohms), the secondary side has a 10 Ohms resistor, if the voltage induced on the secondary ...
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0answers
30 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 tree to the points of ...
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0answers
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Conceptual question about Magnetism? [duplicate]

I am confused about Magnetic force whether it does work or NOT because i think that the battery does the word and the magnetic force only redirects the work done by battery into some displacement etc. ...
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1answer
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Deduction of $\mathbf H =\dfrac{\mathbf B}{\mu_0}-\mathbf M$

merry Christmas to all the users! I want to get to $\mathbf H =\dfrac{\mathbf B}{\mu_0}-\mathbf M$ from the superposition principle, like some texts have done in electrostatics with $\mathbf D=\...
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1answer
27 views

Does a block of iron over a magnet distort the magnetic field between them?

Consider an ideal magnet with even field across its pole's surface and a block of iron over it (fig B). (Disregard the "moving coil" for now) The question is: Is the magnetic field between the ...
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1answer
39 views

Electromagnetic Force vs Magnetic Force

I am confused between these two types of forces, what makes them different? For example, a moving ferromagnetic object in a solenoid that moves because of a magnetic field created. Which field would ...
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2answers
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Superconductive magnet as a source of energy?

Could we charge a superconductive magnet and use it as a source of energy?
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1answer
59 views

Induced EMF in single stationary wire

Suppose we have a conducting stationary wire in a uniform magnetic field: $$\mathbf B(t) = kt \mathbf u_z$$ with $k>0$. Assume the wire is a segment that lies on the $xy$ plane and its length is ...
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1answer
34 views

Is there an magnetic field around ideal conductor?

Im gonna dive straight to the point: If you run some current through, say, copper wire you will get a magnetic field around it; that is how the gauss guns work. My questions are: 1) Is it possible ...
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3answers
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Can visible light be affected by magnetism?

I would like to start by saying that I am not a physicist and I don't really know a lot about the subject! We all know that without Earth's magnetic field, electromagnetic radiation from the sun ...