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
60 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 ...
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1answer
79 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
50 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
19 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
16 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 ...
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0answers
12 views

What causes a larger (longer) electrical arc when using a tesla coil

So, I really don't know much about this subject, if any at all, but I'd like to do a project on it. I've done some testing with my tesla coil and there appears to be a trend such that a larger ...
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0answers
10 views

What is an approximation for the B-field of a bar magnet?

I've found the following equation in this source: $$B_\text{N,S} = \frac{\mu m}{4\pi r_\text{N,S}^2}$$ Where $r$ is the distance of "one pole"? I do not get how this can be well defined. The effective ...
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0answers
14 views

Will diamagnetic behave as magnet to other magnets when placed in magnetic fields? [duplicate]

If we use magnetic field on diamagnetic.Will it behave as magnet? According to diamagnetic metals they create opposing magnetic field.Is that mean that diamagnetic become magnet itself? Will it ...
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1answer
29 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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0answers
81 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 $2v_f$. While the droplet is in rest on a surface, if I approach two magnets in ...
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0answers
22 views

Where is the positive pole on a toroid magnet?

What dictates which direction the poles point on a toroid magnet? Assuming you set up magnets touching positive to negative assembled in a toroid shape. It is made out of neodymium magnets so there is ...
2
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1answer
93 views

Why is there no induced electric field in the experiment (Faraday's Law)

Below are three circuit diagrams for each of Faraday's experiments that allowed Faraday to come up with Faraday's Law. In Griffiths' Introduction to Electrodynamics Griffiths states (on page 302 of ...
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1answer
78 views

Is there any material that is NOT conductive and IS magnetically attractive?

Is there any material which is NOT conductive and IS magnetically attractive? I am in need of a material which I can shape and use within a machine. It must be very attracted to magnets similarly to ...
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0answers
59 views

Peierls substitution vs minimal coupling

In the presence of vector potential (let's assume it's uniform), a tight-binding Hamiltonian will be changed according to the Peierls substitution: $t_{ij}c_i^{\dagger}c_j \to ...
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0answers
10 views

How does magnetic field leverage exchange interaction?

A 1 Tesla magnetic field corresponds to the energy of less than a millielectronvolt. However, fields of that order seem to saturate the magnetization of many solids, be they ferromagnets or ...
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1answer
52 views

How can we define the energy stored in a (conservative) force field?

I have come to know from my textbook that energy is stored in the E-field of a capacitor, in the B-field of an inductor and so on. Take the example of an inductor. The derivation bewilders me ...
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1answer
72 views

why in IYPT problem it said that the non-ferromagnetic disk repel?!how?

for the shaded-pole motor, our rotatable disk is paramagnetic, so it must be attracted to the magnetic field of the inductor. but in the question it said it repelled. does that para disk increase the ...
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4answers
192 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
93 views

If earth's magnetic field disappeared, would cosmic radiation lead to increased radioactivity?

This is about the effect of cosmic radiation on earth. Is it the type of radiation that could make things radioactive? So if earth's magnetic field weakened considerably (such as could happen if it ...
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1answer
59 views

Can a magnetic field be focused at a distance?

There are interesting arrangements of magnets that can strengthen the field in some places while weakening it in others. This is discussed in Can magnetic fields be redirected and focused at one ...
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1answer
28 views

Mu-metal Magnetic shielding

If I want to have a magnetic field only at only one point (or line) in the box. If I will enclose the box with mu-metal and leave a hole a few millimetres in size in it, will it work? Thank you.
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1answer
46 views

How to convert EM fields to EM waves?

How a body producing electricity and magnetic fields become a body radiating electromagnetic waves?
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2answers
45 views

Magnetic Field and Flow of Vector Potential

I am sorry, when my question is not really concrete, but here we go. Consider the Hamiltonian function $$H(x, \xi) = \frac{1}{2m}\bigl|\xi - eA(x)\bigr|^2$$ corresponding to a charged particle in a ...
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1answer
53 views

Constant magnetic field attenuation by µ-metal (mu-metal)

I am interested in the magnetic field attenuation by µ-metal. Specifically shielding from earth's magnetic field $\boldsymbol{H}_E$ through closed cylindrical layers of such a metal, yielding an ...
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0answers
32 views

can magnet used in engines

My friend has told an idea that if the same poled magnets are placed in the motors instead of engines,it will produce the ultimate energy.because same poles are repelling each other. is it possible?
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1answer
29 views

Larmor precession for time-changing magnetic field?

Wikipedia gives the formula for Larmor precession for the magnetic moment in an external field ${\mathbf B}$. But nothing at all is mentioned about whether the field can have a time dependence. Since ...
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1answer
42 views

Does the magnetic anisotropy state only have two possible directions?

Wikipedia says "The magnetic moment of magnetically anisotropic materials will tend to align with an easy axis". Does this mean that it is completely impossible to orient the magnetic moment with any ...
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1answer
66 views

Is there a magnetic line that is a Eucliden straight line?

In my (though few) experiences, magnetic lines are always curved (with respect to a Euclidean plane). I have never seen there is any magnetic line that is Euclidean straight. If there is a magnetic ...
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2answers
85 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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1answer
105 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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1answer
34 views

Helmhoz coil - Define the magnetic field

I have to calculate the magnetic field at point x = R/2 (R is the separation between the two coils). I see why, for one coil, we only take the component along x from the B field as the values along ...
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1answer
58 views

How can a magnetic field produce an emf if the force produced does no work?

In the textbook I'm reading it gives an example of where a person pulls a rectangular wire with a velocity $v$ and the left side of that wire is in a uniform magnetic field. After some ...
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1answer
56 views

Can metal rods detect underground wires?

Until not long ago, I was working in the drilling and infrastructure business. Some people I was working with used metal rods as a "quick and dirty" method of detecting underground wiring, before ...
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0answers
37 views

Insulation for magnetic fields [duplicate]

How can I insulate conductors independently one off the other, where they pass through a magnetic field? Are there a techniques or alloys? There is a issue how to insulate copper wire where current ...
5
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1answer
52 views

Is a superconductor perfectly opaque?

Because of the Meissner effect, no magnetic fields can pierce through the body of a superconductor. Since EM waves need both their electric and magnetic field components, it cannot pierce through the ...
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1answer
87 views

Magnetic fields in transformers and back emf?

i am having some trouble with understanding the magnetic fields inside transformers and how they relate to back emf. My first query is: is the magnetic field produced inside the soft iron core ...
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1answer
76 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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1answer
58 views

Lifetime of the magnetization of a ferromagnet

In a ferromagnetic material, there's spontaneous magnetisation, meaning in the absence of a $\mathbf{B}$ field $\mathbf{M}\neq 0.$ This means that there may be different domains in the sample where ...
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4answers
159 views

Can current be induced in a superconductor?

Moving a magnet close to a conductor induces a current. If it consists of a superconducting material with resistance $R=0$, then my textbook says: Then the induced current will continue to flow ...
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1answer
48 views

What force does a magnetic field of a certain strength apply to an object?

Disclaimer: This question is mostly to fact-check an "Elementary" episode and is not home work related at all. For the curious, in that episode, a "20 tesla magnet" is used to propel bullets inside an ...
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2answers
97 views

Why is there a magnetic field around a magnet if there are no charges moving? [duplicate]

From what I understand, the magnetic force is just a relativistic effect of the electric force, and I understand how this is can be the case when considering the magnetic field generated by a current- ...
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1answer
25 views

Would a magnet still work on the outside of an oil filter?

If I attach a magnet to the outside of an oil filter (aiming to trap small ferro-magnetic particles that would otherwise pass through the filter) would it work? Yes I mean would the magnet still ...
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1answer
28 views

Magnetic Response of Stainless Steel

Is the austenitic stainless steels, like the common 300-serie, 100% NONMAGNETIC? Why some screws or bolts made of stainless steel, 300-serie, respond slightly to a quite strong magnetic field?
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0answers
33 views

Can electromagnetic fields be measured from a distance?

I know that direct measurements of electromagnetic fields can only tell information about the field near the probes, but I am curious if there is a way to measure the electromagnetic field in a not ...
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1answer
50 views

Magnetic field between two concentric inductors

Suppose we have two inductors with $n_1$ and $n_2$ turns, of radii $R_1$ and $R_2$ $(R_1 > R_2)$ respectively and length $l$. They are aligned concentrically and the smaller inductor is wholly ...
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1answer
48 views

Reactive near field for Wireless Power Transfer (WPT)

In literature it is stated that in reactive near field using high-Q coils in resonance the efficiency does not depend on coupling (ie. distance) and that coupling only has influence on rate of energy ...
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1answer
31 views

Why does a spinning nucleon generate a magnetic field?

I am trying to understand how NMR works, but I am not sure why a spinning nucleon produces a magnetic field. Is this a consequence of the quark structure inside?
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0answers
43 views

Calculation of Magnetisation current$(I_m)$

A Permanent magnet in the shape of a thin cylinder of length $10 \;\mathcal{cm}$ has $M=10^6A/m$. Calculate the Magnetisation Current $I_m$ (Here $M$ is the intensity of magnetisation) My ...
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1answer
37 views

Can a unique position be inferred by measuring the magnetic field around a disk magnet?

I was wondering, assuming we have a disk magnet and we measure the magnetic flux density components at ANY point around the magnet (where it is still relevant), is it possible to conclude which point ...
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2answers
55 views

Magnons contribution to spontaneous magnetization

In Statistical Physics part II of Landau's course in theoretical physics it is stated that the magnon part of the spontaneous magnetization can be calculated as $$ M_m \equiv M(T) - M(0) = ...